[Keyboard] Convert Corne Keyboard to Split Common (#6001)

* [Keyboard] Convert Corne Keyboard to Split Common

* Add VIA Support

* Makes sure that ol(e)d and new OLED implementation can't coexist

* Add licensing header to files

* Add changes based on feedback from foostan

* Fixes

17 files changed, 2090 insertions, 0 deletions

diff --git a/keyboards/crkbd/rev1/legacy/config.h b/keyboards/crkbd/rev1/legacy/config.h
new file mode 100644
index 0000000000..9e3676414c
--- /dev/null
+++ b/keyboards/crkbd/rev1/legacy/config.h
@@ -0,0 +1,23 @@
+/*
+Copyright 2012 Jun Wako <wakojun@gmail.com>
+Copyright 2015 Jack Humbert
+
+This program is free software: you can redistribute it and/or modify
+it under the terms of the GNU General Public License as published by
+the Free Software Foundation, either version 2 of the License, or
+(at your option) any later version.
+
+This program is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+GNU General Public License for more details.
+
+You should have received a copy of the GNU General Public License
+along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+#pragma once
+
+#include <serial_config.h>
+
+#define PRODUCT         Corne Keyboard Rev.1 (Legacy Split)
diff --git a/keyboards/crkbd/rev1/legacy/i2c.c b/keyboards/crkbd/rev1/legacy/i2c.c
new file mode 100644
index 0000000000..7b45c3f866
--- /dev/null
+++ b/keyboards/crkbd/rev1/legacy/i2c.c
@@ -0,0 +1,162 @@
+#include <util/twi.h>
+#include <avr/io.h>
+#include <stdlib.h>
+#include <avr/interrupt.h>
+#include <util/twi.h>
+#include <stdbool.h>
+#include "i2c.h"
+
+#if defined(USE_I2C) || defined(USE_MATRIX_I2C)
+
+// Limits the amount of we wait for any one i2c transaction.
+// Since were running SCL line 100kHz (=> 10μs/bit), and each transactions is
+// 9 bits, a single transaction will take around 90μs to complete.
+//
+// (F_CPU/SCL_CLOCK)  =>  # of μC cycles to transfer a bit
+// poll loop takes at least 8 clock cycles to execute
+#define I2C_LOOP_TIMEOUT (9+1)*(F_CPU/SCL_CLOCK)/8
+
+#define BUFFER_POS_INC() (slave_buffer_pos = (slave_buffer_pos+1)%SLAVE_BUFFER_SIZE)
+
+volatile uint8_t i2c_slave_buffer[SLAVE_BUFFER_SIZE];
+
+static volatile uint8_t slave_buffer_pos;
+static volatile bool slave_has_register_set = false;
+
+// Wait for an i2c operation to finish
+inline static
+void i2c_delay(void) {
+  uint16_t lim = 0;
+  while(!(TWCR & (1<<TWINT)) && lim < I2C_LOOP_TIMEOUT)
+    lim++;
+
+  // easier way, but will wait slightly longer
+  // _delay_us(100);
+}
+
+// Setup twi to run at 100kHz or 400kHz (see ./i2c.h SCL_CLOCK)
+void i2c_master_init(void) {
+  // no prescaler
+  TWSR = 0;
+  // Set TWI clock frequency to SCL_CLOCK. Need TWBR>10.
+  // Check datasheets for more info.
+  TWBR = ((F_CPU/SCL_CLOCK)-16)/2;
+}
+
+// Start a transaction with the given i2c slave address. The direction of the
+// transfer is set with I2C_READ and I2C_WRITE.
+// returns: 0 => success
+//          1 => error
+uint8_t i2c_master_start(uint8_t address) {
+  TWCR = (1<<TWINT) | (1<<TWEN) | (1<<TWSTA);
+
+  i2c_delay();
+
+  // check that we started successfully
+  if ( (TW_STATUS != TW_START) && (TW_STATUS != TW_REP_START))
+    return 1;
+
+  TWDR = address;
+  TWCR = (1<<TWINT) | (1<<TWEN);
+
+  i2c_delay();
+
+  if ( (TW_STATUS != TW_MT_SLA_ACK) && (TW_STATUS != TW_MR_SLA_ACK) )
+    return 1; // slave did not acknowledge
+  else
+    return 0; // success
+}
+
+
+// Finish the i2c transaction.
+void i2c_master_stop(void) {
+  TWCR = (1<<TWINT) | (1<<TWEN) | (1<<TWSTO);
+
+  uint16_t lim = 0;
+  while(!(TWCR & (1<<TWSTO)) && lim < I2C_LOOP_TIMEOUT)
+    lim++;
+}
+
+// Write one byte to the i2c slave.
+// returns 0 => slave ACK
+//         1 => slave NACK
+uint8_t i2c_master_write(uint8_t data) {
+  TWDR = data;
+  TWCR = (1<<TWINT) | (1<<TWEN);
+
+  i2c_delay();
+
+  // check if the slave acknowledged us
+  return (TW_STATUS == TW_MT_DATA_ACK) ? 0 : 1;
+}
+
+// Read one byte from the i2c slave. If ack=1 the slave is acknowledged,
+// if ack=0 the acknowledge bit is not set.
+// returns: byte read from i2c device
+uint8_t i2c_master_read(int ack) {
+  TWCR = (1<<TWINT) | (1<<TWEN) | (ack<<TWEA);
+
+  i2c_delay();
+  return TWDR;
+}
+
+void i2c_reset_state(void) {
+  TWCR = 0;
+}
+
+void i2c_slave_init(uint8_t address) {
+  TWAR = address << 0; // slave i2c address
+  // TWEN  - twi enable
+  // TWEA  - enable address acknowledgement
+  // TWINT - twi interrupt flag
+  // TWIE  - enable the twi interrupt
+  TWCR = (1<<TWIE) | (1<<TWEA) | (1<<TWINT) | (1<<TWEN);
+}
+
+ISR(TWI_vect);
+
+ISR(TWI_vect) {
+  uint8_t ack = 1;
+  switch(TW_STATUS) {
+    case TW_SR_SLA_ACK:
+      // this device has been addressed as a slave receiver
+      slave_has_register_set = false;
+      break;
+
+    case TW_SR_DATA_ACK:
+      // this device has received data as a slave receiver
+      // The first byte that we receive in this transaction sets the location
+      // of the read/write location of the slaves memory that it exposes over
+      // i2c.  After that, bytes will be written at slave_buffer_pos, incrementing
+      // slave_buffer_pos after each write.
+      if(!slave_has_register_set) {
+        slave_buffer_pos = TWDR;
+        // don't acknowledge the master if this memory loctaion is out of bounds
+        if ( slave_buffer_pos >= SLAVE_BUFFER_SIZE ) {
+          ack = 0;
+          slave_buffer_pos = 0;
+        }
+        slave_has_register_set = true;
+      } else {
+        i2c_slave_buffer[slave_buffer_pos] = TWDR;
+        BUFFER_POS_INC();
+      }
+      break;
+
+    case TW_ST_SLA_ACK:
+    case TW_ST_DATA_ACK:
+      // master has addressed this device as a slave transmitter and is
+      // requesting data.
+      TWDR = i2c_slave_buffer[slave_buffer_pos];
+      BUFFER_POS_INC();
+      break;
+
+    case TW_BUS_ERROR: // something went wrong, reset twi state
+      TWCR = 0;
+    default:
+      break;
+  }
+  // Reset everything, so we are ready for the next TWI interrupt
+  TWCR |= (1<<TWIE) | (1<<TWINT) | (ack<<TWEA) | (1<<TWEN);
+}
+#endif
diff --git a/keyboards/crkbd/rev1/legacy/i2c.h b/keyboards/crkbd/rev1/legacy/i2c.h
new file mode 100644
index 0000000000..710662c7ab
--- /dev/null
+++ b/keyboards/crkbd/rev1/legacy/i2c.h
@@ -0,0 +1,46 @@
+#pragma once
+
+#include <stdint.h>
+
+#ifndef F_CPU
+#define F_CPU 16000000UL
+#endif
+
+#define I2C_READ 1
+#define I2C_WRITE 0
+
+#define I2C_ACK 1
+#define I2C_NACK 0
+
+#define SLAVE_BUFFER_SIZE 0x10
+
+// i2c SCL clock frequency 400kHz
+#define SCL_CLOCK  400000L
+
+extern volatile uint8_t i2c_slave_buffer[SLAVE_BUFFER_SIZE];
+
+void i2c_master_init(void);
+uint8_t i2c_master_start(uint8_t address);
+void i2c_master_stop(void);
+uint8_t i2c_master_write(uint8_t data);
+uint8_t i2c_master_read(int);
+void i2c_reset_state(void);
+void i2c_slave_init(uint8_t address);
+
+
+static inline unsigned char i2c_start_read(unsigned char addr) {
+  return i2c_master_start((addr << 1) | I2C_READ);
+}
+
+static inline unsigned char i2c_start_write(unsigned char addr) {
+  return i2c_master_start((addr << 1) | I2C_WRITE);
+}
+
+// from SSD1306 scrips
+extern unsigned char i2c_rep_start(unsigned char addr);
+extern void i2c_start_wait(unsigned char addr);
+extern unsigned char i2c_readAck(void);
+extern unsigned char i2c_readNak(void);
+extern unsigned char i2c_read(unsigned char ack);
+
+#define i2c_read(ack)  (ack) ? i2c_readAck() : i2c_readNak();
diff --git a/keyboards/crkbd/rev1/legacy/legacy.c b/keyboards/crkbd/rev1/legacy/legacy.c
new file mode 100644
index 0000000000..595ff1eaf7
--- /dev/null
+++ b/keyboards/crkbd/rev1/legacy/legacy.c
@@ -0,0 +1,19 @@
+/*
+Copyright 2019 @foostan
+Copyright 2020 Drashna Jaelre <@drashna>
+
+This program is free software: you can redistribute it and/or modify
+it under the terms of the GNU General Public License as published by
+the Free Software Foundation, either version 2 of the License, or
+(at your option) any later version.
+
+This program is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+GNU General Public License for more details.
+
+You should have received a copy of the GNU General Public License
+along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+#include "legacy.h"
diff --git a/keyboards/crkbd/rev1/legacy/legacy.h b/keyboards/crkbd/rev1/legacy/legacy.h
new file mode 100644
index 0000000000..6c6308e592
--- /dev/null
+++ b/keyboards/crkbd/rev1/legacy/legacy.h
@@ -0,0 +1,21 @@
+/*
+Copyright 2019 @foostan
+Copyright 2020 Drashna Jaelre <@drashna>
+
+This program is free software: you can redistribute it and/or modify
+it under the terms of the GNU General Public License as published by
+the Free Software Foundation, either version 2 of the License, or
+(at your option) any later version.
+
+This program is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+GNU General Public License for more details.
+
+You should have received a copy of the GNU General Public License
+along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+#pragma once
+
+#include "rev1.h"
diff --git a/keyboards/crkbd/rev1/legacy/matrix.c b/keyboards/crkbd/rev1/legacy/matrix.c
new file mode 100644
index 0000000000..46dead369f
--- /dev/null
+++ b/keyboards/crkbd/rev1/legacy/matrix.c
@@ -0,0 +1,393 @@
+/*
+Copyright 2012 Jun Wako <wakojun@gmail.com>
+
+This program is free software: you can redistribute it and/or modify
+it under the terms of the GNU General Public License as published by
+the Free Software Foundation, either version 2 of the License, or
+(at your option) any later version.
+
+This program is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+GNU General Public License for more details.
+
+You should have received a copy of the GNU General Public License
+along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+/*
+ * scan matrix
+ */
+#include <stdint.h>
+#include <stdbool.h>
+#include <string.h>
+#include <avr/io.h>
+#include <avr/wdt.h>
+#include <avr/interrupt.h>
+#include <util/delay.h>
+#include "print.h"
+#include "debug.h"
+#include "util.h"
+#include "matrix.h"
+#include "split_util.h"
+#include "quantum.h"
+
+#ifdef USE_MATRIX_I2C
+#  include "i2c.h"
+#else // USE_SERIAL
+#  include "split_scomm.h"
+#endif
+
+#ifndef DEBOUNCE
+#  define DEBOUNCE	5
+#endif
+
+#define ERROR_DISCONNECT_COUNT 5
+
+static uint8_t debouncing = DEBOUNCE;
+static const int ROWS_PER_HAND = MATRIX_ROWS/2;
+static uint8_t error_count = 0;
+uint8_t is_master = 0 ;
+
+static const uint8_t row_pins[MATRIX_ROWS] = MATRIX_ROW_PINS;
+static const uint8_t col_pins[MATRIX_COLS] = MATRIX_COL_PINS;
+
+/* matrix state(1:on, 0:off) */
+static matrix_row_t matrix[MATRIX_ROWS];
+static matrix_row_t matrix_debouncing[MATRIX_ROWS];
+
+static matrix_row_t read_cols(void);
+static void init_cols(void);
+static void unselect_rows(void);
+static void select_row(uint8_t row);
+static uint8_t matrix_master_scan(void);
+
+
+__attribute__ ((weak))
+void matrix_init_kb(void) {
+    matrix_init_user();
+}
+
+__attribute__ ((weak))
+void matrix_scan_kb(void) {
+    matrix_scan_user();
+}
+
+__attribute__ ((weak))
+void matrix_init_user(void) {
+}
+
+__attribute__ ((weak))
+void matrix_scan_user(void) {
+}
+
+inline
+uint8_t matrix_rows(void)
+{
+    return MATRIX_ROWS;
+}
+
+inline
+uint8_t matrix_cols(void)
+{
+    return MATRIX_COLS;
+}
+
+void tx_rx_leds_init(void)
+{
+#ifndef NO_DEBUG_LEDS
+    setPinOutput(B0);
+    setPinOutput(D5);
+    writePinHigh(B0);
+    writePinHigh(D5);
+#endif
+}
+
+void tx_led_on(void)
+{
+#ifndef NO_DEBUG_LEDS
+    writePinLow(D5);
+#endif
+}
+
+void tx_led_off(void)
+{
+#ifndef NO_DEBUG_LEDS
+    writePinHigh(D5);
+#endif
+}
+
+void rx_led_on(void)
+{
+#ifndef NO_DEBUG_LEDS
+    writePinLow(B0);
+#endif
+}
+
+void rx_led_off(void)
+{
+#ifndef NO_DEBUG_LEDS
+    writePinHigh(B0);
+#endif
+}
+
+
+void matrix_init(void)
+{
+    split_keyboard_setup();
+
+    // initialize row and col
+    unselect_rows();
+    init_cols();
+
+    tx_rx_leds_init();
+
+    // initialize matrix state: all keys off
+    for (uint8_t i=0; i < MATRIX_ROWS; i++) {
+        matrix[i] = 0;
+        matrix_debouncing[i] = 0;
+    }
+
+    is_master = has_usb();
+
+    matrix_init_quantum();
+}
+
+uint8_t _matrix_scan(void)
+{
+    // Right hand is stored after the left in the matirx so, we need to offset it
+    int offset = isLeftHand ? 0 : (ROWS_PER_HAND);
+
+    for (uint8_t i = 0; i < ROWS_PER_HAND; i++) {
+        select_row(i);
+        _delay_us(30);  // without this wait read unstable value.
+        matrix_row_t cols = read_cols();
+        if (matrix_debouncing[i+offset] != cols) {
+            matrix_debouncing[i+offset] = cols;
+            debouncing = DEBOUNCE;
+        }
+        unselect_rows();
+    }
+
+    if (debouncing) {
+        if (--debouncing) {
+            _delay_ms(1);
+        } else {
+            for (uint8_t i = 0; i < ROWS_PER_HAND; i++) {
+                matrix[i+offset] = matrix_debouncing[i+offset];
+            }
+        }
+    }
+
+    return 1;
+}
+
+#ifdef USE_MATRIX_I2C
+
+// Get rows from other half over i2c
+int i2c_transaction(void) {
+    int slaveOffset = (isLeftHand) ? (ROWS_PER_HAND) : 0;
+
+    int err = i2c_master_start(SLAVE_I2C_ADDRESS + I2C_WRITE);
+    if (err) goto i2c_error;
+
+    // start of matrix stored at 0x00
+    err = i2c_master_write(0x00);
+    if (err) goto i2c_error;
+
+    // Start read
+    err = i2c_master_start(SLAVE_I2C_ADDRESS + I2C_READ);
+    if (err) goto i2c_error;
+
+    if (!err) {
+        int i;
+        for (i = 0; i < ROWS_PER_HAND-1; ++i) {
+            matrix[slaveOffset+i] = i2c_master_read(I2C_ACK);
+        }
+        matrix[slaveOffset+i] = i2c_master_read(I2C_NACK);
+        i2c_master_stop();
+    } else {
+i2c_error: // the cable is disconnceted, or something else went wrong
+        i2c_reset_state();
+        return err;
+    }
+
+    return 0;
+}
+
+#else // USE_SERIAL
+
+int serial_transaction(int master_changed) {
+    int slaveOffset = (isLeftHand) ? (ROWS_PER_HAND) : 0;
+#ifdef SERIAL_USE_MULTI_TRANSACTION
+    int ret=serial_update_buffers(master_changed);
+#else
+    int ret=serial_update_buffers();
+#endif
+    if (ret ) {
+        if(ret==2) rx_led_on();
+        return 1;
+    }
+    rx_led_off();
+    memcpy(&matrix[slaveOffset],
+        (void *)serial_slave_buffer, SERIAL_SLAVE_BUFFER_LENGTH);
+    return 0;
+}
+#endif
+
+uint8_t matrix_scan(void)
+{
+    if (is_master) {
+        matrix_master_scan();
+    }else{
+        matrix_slave_scan();
+        int offset = (isLeftHand) ? ROWS_PER_HAND : 0;
+        memcpy(&matrix[offset],
+               (void *)serial_master_buffer, SERIAL_MASTER_BUFFER_LENGTH);
+        matrix_scan_quantum();
+    }
+    return 1;
+}
+
+
+uint8_t matrix_master_scan(void) {
+
+    int ret = _matrix_scan();
+    int mchanged = 1;
+
+    int offset = (isLeftHand) ? 0 : ROWS_PER_HAND;
+
+#ifdef USE_MATRIX_I2C
+//    for (int i = 0; i < ROWS_PER_HAND; ++i) {
+        /* i2c_slave_buffer[i] = matrix[offset+i]; */
+//        i2c_slave_buffer[i] = matrix[offset+i];
+//    }
+#else // USE_SERIAL
+  #ifdef SERIAL_USE_MULTI_TRANSACTION
+    mchanged = memcmp((void *)serial_master_buffer,
+		      &matrix[offset], SERIAL_MASTER_BUFFER_LENGTH);
+  #endif
+    memcpy((void *)serial_master_buffer,
+	   &matrix[offset], SERIAL_MASTER_BUFFER_LENGTH);
+#endif
+
+#ifdef USE_MATRIX_I2C
+    if( i2c_transaction() ) {
+#else // USE_SERIAL
+    if( serial_transaction(mchanged) ) {
+#endif
+        // turn on the indicator led when halves are disconnected
+        tx_led_on();
+
+        error_count++;
+
+        if (error_count > ERROR_DISCONNECT_COUNT) {
+            // reset other half if disconnected
+            int slaveOffset = (isLeftHand) ? (ROWS_PER_HAND) : 0;
+            for (int i = 0; i < ROWS_PER_HAND; ++i) {
+                matrix[slaveOffset+i] = 0;
+            }
+        }
+    } else {
+        // turn off the indicator led on no error
+        tx_led_off();
+        error_count = 0;
+    }
+    matrix_scan_quantum();
+    return ret;
+}
+
+void matrix_slave_scan(void) {
+    _matrix_scan();
+
+    int offset = (isLeftHand) ? 0 : ROWS_PER_HAND;
+
+#ifdef USE_MATRIX_I2C
+    for (int i = 0; i < ROWS_PER_HAND; ++i) {
+        /* i2c_slave_buffer[i] = matrix[offset+i]; */
+        i2c_slave_buffer[i] = matrix[offset+i];
+    }
+#else // USE_SERIAL
+  #ifdef SERIAL_USE_MULTI_TRANSACTION
+    int change = 0;
+  #endif
+    for (int i = 0; i < ROWS_PER_HAND; ++i) {
+  #ifdef SERIAL_USE_MULTI_TRANSACTION
+        if( serial_slave_buffer[i] != matrix[offset+i] )
+	    change = 1;
+  #endif
+        serial_slave_buffer[i] = matrix[offset+i];
+    }
+  #ifdef SERIAL_USE_MULTI_TRANSACTION
+    slave_buffer_change_count += change;
+  #endif
+#endif
+}
+
+bool matrix_is_modified(void)
+{
+    if (debouncing) return false;
+    return true;
+}
+
+inline
+bool matrix_is_on(uint8_t row, uint8_t col)
+{
+    return (matrix[row] & ((matrix_row_t)1<<col));
+}
+
+inline
+matrix_row_t matrix_get_row(uint8_t row)
+{
+    return matrix[row];
+}
+
+void matrix_print(void)
+{
+    print("\nr/c 0123456789ABCDEF\n");
+    for (uint8_t row = 0; row < MATRIX_ROWS; row++) {
+        phex(row); print(": ");
+        pbin_reverse16(matrix_get_row(row));
+        print("\n");
+    }
+}
+
+uint8_t matrix_key_count(void)
+{
+    uint8_t count = 0;
+    for (uint8_t i = 0; i < MATRIX_ROWS; i++) {
+        count += bitpop16(matrix[i]);
+    }
+    return count;
+}
+
+static void  init_cols(void)
+{
+    for(int x = 0; x < MATRIX_COLS; x++) {
+        _SFR_IO8((col_pins[x] >> 4) + 1) &=  ~_BV(col_pins[x] & 0xF);
+        _SFR_IO8((col_pins[x] >> 4) + 2) |= _BV(col_pins[x] & 0xF);
+    }
+}
+
+static matrix_row_t read_cols(void)
+{
+    matrix_row_t result = 0;
+    for(int x = 0; x < MATRIX_COLS; x++) {
+        result |= (_SFR_IO8(col_pins[x] >> 4) & _BV(col_pins[x] & 0xF)) ? 0 : (1 << x);
+    }
+    return result;
+}
+
+static void unselect_rows(void)
+{
+    for(int x = 0; x < ROWS_PER_HAND; x++) {
+        _SFR_IO8((row_pins[x] >> 4) + 1) &=  ~_BV(row_pins[x] & 0xF);
+        _SFR_IO8((row_pins[x] >> 4) + 2) |= _BV(row_pins[x] & 0xF);
+    }
+}
+
+static void select_row(uint8_t row)
+{
+    _SFR_IO8((row_pins[row] >> 4) + 1) |=  _BV(row_pins[row] & 0xF);
+    _SFR_IO8((row_pins[row] >> 4) + 2) &= ~_BV(row_pins[row] & 0xF);
+}
diff --git a/keyboards/crkbd/rev1/legacy/post_config.h b/keyboards/crkbd/rev1/legacy/post_config.h
new file mode 100644
index 0000000000..b3d6346cc8
--- /dev/null
+++ b/keyboards/crkbd/rev1/legacy/post_config.h
@@ -0,0 +1,27 @@
+/*
+Copyright 2019 @foostan
+Copyright 2020 Drashna Jaelre <@drashna>
+
+This program is free software: you can redistribute it and/or modify
+it under the terms of the GNU General Public License as published by
+the Free Software Foundation, either version 2 of the License, or
+(at your option) any later version.
+
+This program is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+GNU General Public License for more details.
+
+You should have received a copy of the GNU General Public License
+along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+#pragma once
+
+#ifdef SSD1306OLED
+#    define USE_I2C
+#endif
+
+#if defined(OLED_DRIVER_ENABLE) && (defined(USE_I2C) || defined(USE_MATRIX_I2C))
+#    error Cannot use both legacy i2c driver and new i2c_master driver at the same time. Undefine USE_I2C and/or USE_MATRIX_I2C
+#endif
diff --git a/keyboards/crkbd/rev1/legacy/rules.mk b/keyboards/crkbd/rev1/legacy/rules.mk
new file mode 100644
index 0000000000..2bef242977
--- /dev/null
+++ b/keyboards/crkbd/rev1/legacy/rules.mk
@@ -0,0 +1,7 @@
+CUSTOM_MATRIX = yes
+
+SRC += 	matrix.c \
+		split_util.c \
+		split_scomm.c
+
+QUANTUM_LIB_SRC += i2c.c serial.c
diff --git a/keyboards/crkbd/rev1/legacy/serial.c b/keyboards/crkbd/rev1/legacy/serial.c
new file mode 100644
index 0000000000..f6293c3dc2
--- /dev/null
+++ b/keyboards/crkbd/rev1/legacy/serial.c
@@ -0,0 +1,589 @@
+/*
+ * WARNING: be careful changing this code, it is very timing dependent
+ *
+ * 2018-10-28 checked
+ *  avr-gcc 4.9.2
+ *  avr-gcc 5.4.0
+ *  avr-gcc 7.3.0
+ */
+
+#ifndef F_CPU
+#define F_CPU 16000000
+#endif
+
+#include <avr/io.h>
+#include <avr/interrupt.h>
+#include <util/delay.h>
+#include <stddef.h>
+#include <stdbool.h>
+#include "serial.h"
+
+#ifdef SOFT_SERIAL_PIN
+
+#ifdef __AVR_ATmega32U4__
+  // if using ATmega32U4 I2C, can not use PD0 and PD1 in soft serial.
+  #ifdef USE_I2C
+    #if SOFT_SERIAL_PIN == D0 || SOFT_SERIAL_PIN == D1
+      #error Using ATmega32U4 I2C, so can not use PD0, PD1
+    #endif
+  #endif
+
+  #if SOFT_SERIAL_PIN >= D0 && SOFT_SERIAL_PIN <= D3
+    #define SERIAL_PIN_DDR   DDRD
+    #define SERIAL_PIN_PORT  PORTD
+    #define SERIAL_PIN_INPUT PIND
+    #if SOFT_SERIAL_PIN == D0
+      #define SERIAL_PIN_MASK _BV(PD0)
+      #define EIMSK_BIT       _BV(INT0)
+      #define EICRx_BIT       (~(_BV(ISC00) | _BV(ISC01)))
+      #define SERIAL_PIN_INTERRUPT INT0_vect
+    #elif  SOFT_SERIAL_PIN == D1
+      #define SERIAL_PIN_MASK _BV(PD1)
+      #define EIMSK_BIT       _BV(INT1)
+      #define EICRx_BIT       (~(_BV(ISC10) | _BV(ISC11)))
+      #define SERIAL_PIN_INTERRUPT INT1_vect
+    #elif  SOFT_SERIAL_PIN == D2
+      #define SERIAL_PIN_MASK _BV(PD2)
+      #define EIMSK_BIT       _BV(INT2)
+      #define EICRx_BIT       (~(_BV(ISC20) | _BV(ISC21)))
+      #define SERIAL_PIN_INTERRUPT INT2_vect
+    #elif  SOFT_SERIAL_PIN == D3
+      #define SERIAL_PIN_MASK _BV(PD3)
+      #define EIMSK_BIT       _BV(INT3)
+      #define EICRx_BIT       (~(_BV(ISC30) | _BV(ISC31)))
+      #define SERIAL_PIN_INTERRUPT INT3_vect
+    #endif
+  #elif  SOFT_SERIAL_PIN == E6
+    #define SERIAL_PIN_DDR   DDRE
+    #define SERIAL_PIN_PORT  PORTE
+    #define SERIAL_PIN_INPUT PINE
+    #define SERIAL_PIN_MASK  _BV(PE6)
+    #define EIMSK_BIT        _BV(INT6)
+    #define EICRx_BIT        (~(_BV(ISC60) | _BV(ISC61)))
+    #define SERIAL_PIN_INTERRUPT INT6_vect
+  #else
+  #error invalid SOFT_SERIAL_PIN value
+  #endif
+
+#else
+ #error serial.c now support ATmega32U4 only
+#endif
+
+//////////////// for backward compatibility ////////////////////////////////
+#ifndef SERIAL_USE_MULTI_TRANSACTION
+/* --- USE Simple API (OLD API, compatible with let's split serial.c) */
+  #if SERIAL_SLAVE_BUFFER_LENGTH > 0
+  uint8_t volatile serial_slave_buffer[SERIAL_SLAVE_BUFFER_LENGTH] = {0};
+  #endif
+  #if SERIAL_MASTER_BUFFER_LENGTH > 0
+  uint8_t volatile serial_master_buffer[SERIAL_MASTER_BUFFER_LENGTH] = {0};
+  #endif
+  uint8_t volatile status0 = 0;
+
+SSTD_t transactions[] = {
+    { (uint8_t *)&status0,
+  #if SERIAL_MASTER_BUFFER_LENGTH > 0
+      sizeof(serial_master_buffer), (uint8_t *)serial_master_buffer,
+  #else
+      0, (uint8_t *)NULL,
+  #endif
+  #if SERIAL_SLAVE_BUFFER_LENGTH > 0
+      sizeof(serial_slave_buffer), (uint8_t *)serial_slave_buffer
+  #else
+      0, (uint8_t *)NULL,
+  #endif
+  }
+};
+
+void serial_master_init(void)
+{ soft_serial_initiator_init(transactions, TID_LIMIT(transactions)); }
+
+void serial_slave_init(void)
+{ soft_serial_target_init(transactions, TID_LIMIT(transactions)); }
+
+// 0 => no error
+// 1 => slave did not respond
+// 2 => checksum error
+int serial_update_buffers()
+{
+    int result;
+    result = soft_serial_transaction();
+    return result;
+}
+
+#endif // end of Simple API (OLD API, compatible with let's split serial.c)
+////////////////////////////////////////////////////////////////////////////
+
+#define ALWAYS_INLINE __attribute__((always_inline))
+#define NO_INLINE __attribute__((noinline))
+#define _delay_sub_us(x)    __builtin_avr_delay_cycles(x)
+
+// parity check
+#define ODD_PARITY 1
+#define EVEN_PARITY 0
+#define PARITY EVEN_PARITY
+
+#ifdef SERIAL_DELAY
+  // custom setup in config.h
+  // #define TID_SEND_ADJUST 2
+  // #define SERIAL_DELAY 6             // micro sec
+  // #define READ_WRITE_START_ADJUST 30 // cycles
+  // #define READ_WRITE_WIDTH_ADJUST 8 // cycles
+#else
+// ============ Standard setups ============
+
+#ifndef SELECT_SOFT_SERIAL_SPEED
+#define SELECT_SOFT_SERIAL_SPEED 1
+//  0: about 189kbps
+//  1: about 137kbps (default)
+//  2: about 75kbps
+//  3: about 39kbps
+//  4: about 26kbps
+//  5: about 20kbps
+#endif
+
+#if __GNUC__ < 6
+  #define TID_SEND_ADJUST 14
+#else
+  #define TID_SEND_ADJUST 2
+#endif
+
+#if SELECT_SOFT_SERIAL_SPEED == 0
+  // Very High speed
+  #define SERIAL_DELAY 4             // micro sec
+  #if __GNUC__ < 6
+    #define READ_WRITE_START_ADJUST 33 // cycles
+    #define READ_WRITE_WIDTH_ADJUST 3 // cycles
+  #else
+    #define READ_WRITE_START_ADJUST 34 // cycles
+    #define READ_WRITE_WIDTH_ADJUST 7 // cycles
+  #endif
+#elif SELECT_SOFT_SERIAL_SPEED == 1
+  // High speed
+  #define SERIAL_DELAY 6             // micro sec
+  #if __GNUC__ < 6
+    #define READ_WRITE_START_ADJUST 30 // cycles
+    #define READ_WRITE_WIDTH_ADJUST 3 // cycles
+  #else
+    #define READ_WRITE_START_ADJUST 33 // cycles
+    #define READ_WRITE_WIDTH_ADJUST 7 // cycles
+  #endif
+#elif SELECT_SOFT_SERIAL_SPEED == 2
+  // Middle speed
+  #define SERIAL_DELAY 12            // micro sec
+  #define READ_WRITE_START_ADJUST 30 // cycles
+  #if __GNUC__ < 6
+    #define READ_WRITE_WIDTH_ADJUST 3 // cycles
+  #else
+    #define READ_WRITE_WIDTH_ADJUST 7 // cycles
+  #endif
+#elif SELECT_SOFT_SERIAL_SPEED == 3
+  // Low speed
+  #define SERIAL_DELAY 24            // micro sec
+  #define READ_WRITE_START_ADJUST 30 // cycles
+  #if __GNUC__ < 6
+    #define READ_WRITE_WIDTH_ADJUST 3 // cycles
+  #else
+    #define READ_WRITE_WIDTH_ADJUST 7 // cycles
+  #endif
+#elif SELECT_SOFT_SERIAL_SPEED == 4
+  // Very Low speed
+  #define SERIAL_DELAY 36            // micro sec
+  #define READ_WRITE_START_ADJUST 30 // cycles
+  #if __GNUC__ < 6
+    #define READ_WRITE_WIDTH_ADJUST 3 // cycles
+  #else
+    #define READ_WRITE_WIDTH_ADJUST 7 // cycles
+  #endif
+#elif SELECT_SOFT_SERIAL_SPEED == 5
+  // Ultra Low speed
+  #define SERIAL_DELAY 48            // micro sec
+  #define READ_WRITE_START_ADJUST 30 // cycles
+  #if __GNUC__ < 6
+    #define READ_WRITE_WIDTH_ADJUST 3 // cycles
+  #else
+    #define READ_WRITE_WIDTH_ADJUST 7 // cycles
+  #endif
+#else
+#error invalid SELECT_SOFT_SERIAL_SPEED value
+#endif /* SELECT_SOFT_SERIAL_SPEED */
+#endif /* SERIAL_DELAY */
+
+#define SERIAL_DELAY_HALF1 (SERIAL_DELAY/2)
+#define SERIAL_DELAY_HALF2 (SERIAL_DELAY - SERIAL_DELAY/2)
+
+#define SLAVE_INT_WIDTH_US 1
+#ifndef SERIAL_USE_MULTI_TRANSACTION
+  #define SLAVE_INT_RESPONSE_TIME SERIAL_DELAY
+#else
+  #define SLAVE_INT_ACK_WIDTH_UNIT 2
+  #define SLAVE_INT_ACK_WIDTH 4
+#endif
+
+static SSTD_t *Transaction_table = NULL;
+static uint8_t Transaction_table_size = 0;
+
+inline static void serial_delay(void) ALWAYS_INLINE;
+inline static
+void serial_delay(void) {
+  _delay_us(SERIAL_DELAY);
+}
+
+inline static void serial_delay_half1(void) ALWAYS_INLINE;
+inline static
+void serial_delay_half1(void) {
+  _delay_us(SERIAL_DELAY_HALF1);
+}
+
+inline static void serial_delay_half2(void) ALWAYS_INLINE;
+inline static
+void serial_delay_half2(void) {
+  _delay_us(SERIAL_DELAY_HALF2);
+}
+
+inline static void serial_output(void) ALWAYS_INLINE;
+inline static
+void serial_output(void) {
+  SERIAL_PIN_DDR |= SERIAL_PIN_MASK;
+}
+
+// make the serial pin an input with pull-up resistor
+inline static void serial_input_with_pullup(void) ALWAYS_INLINE;
+inline static
+void serial_input_with_pullup(void) {
+  SERIAL_PIN_DDR  &= ~SERIAL_PIN_MASK;
+  SERIAL_PIN_PORT |= SERIAL_PIN_MASK;
+}
+
+inline static uint8_t serial_read_pin(void) ALWAYS_INLINE;
+inline static
+uint8_t serial_read_pin(void) {
+  return !!(SERIAL_PIN_INPUT & SERIAL_PIN_MASK);
+}
+
+inline static void serial_low(void) ALWAYS_INLINE;
+inline static
+void serial_low(void) {
+  SERIAL_PIN_PORT &= ~SERIAL_PIN_MASK;
+}
+
+inline static void serial_high(void) ALWAYS_INLINE;
+inline static
+void serial_high(void) {
+  SERIAL_PIN_PORT |= SERIAL_PIN_MASK;
+}
+
+void soft_serial_initiator_init(SSTD_t *sstd_table, int sstd_table_size)
+{
+    Transaction_table = sstd_table;
+    Transaction_table_size = (uint8_t)sstd_table_size;
+    serial_output();
+    serial_high();
+}
+
+void soft_serial_target_init(SSTD_t *sstd_table, int sstd_table_size)
+{
+    Transaction_table = sstd_table;
+    Transaction_table_size = (uint8_t)sstd_table_size;
+    serial_input_with_pullup();
+
+    // Enable INT0-INT3,INT6
+    EIMSK |= EIMSK_BIT;
+#if SERIAL_PIN_MASK == _BV(PE6)
+    // Trigger on falling edge of INT6
+    EICRB &= EICRx_BIT;
+#else
+    // Trigger on falling edge of INT0-INT3
+    EICRA &= EICRx_BIT;
+#endif
+}
+
+// Used by the sender to synchronize timing with the reciver.
+static void sync_recv(void) NO_INLINE;
+static
+void sync_recv(void) {
+  for (uint8_t i = 0; i < SERIAL_DELAY*5 && serial_read_pin(); i++ ) {
+  }
+  // This shouldn't hang if the target disconnects because the
+  // serial line will float to high if the target does disconnect.
+  while (!serial_read_pin());
+}
+
+// Used by the reciver to send a synchronization signal to the sender.
+static void sync_send(void) NO_INLINE;
+static
+void sync_send(void) {
+  serial_low();
+  serial_delay();
+  serial_high();
+}
+
+// Reads a byte from the serial line
+static uint8_t serial_read_chunk(uint8_t *pterrcount, uint8_t bit) NO_INLINE;
+static uint8_t serial_read_chunk(uint8_t *pterrcount, uint8_t bit) {
+    uint8_t byte, i, p, pb;
+
+  _delay_sub_us(READ_WRITE_START_ADJUST);
+  for( i = 0, byte = 0, p = PARITY; i < bit; i++ ) {
+      serial_delay_half1();   // read the middle of pulses
+      if( serial_read_pin() ) {
+          byte = (byte << 1) | 1; p ^= 1;
+      } else {
+          byte = (byte << 1) | 0; p ^= 0;
+      }
+      _delay_sub_us(READ_WRITE_WIDTH_ADJUST);
+      serial_delay_half2();
+  }
+  /* recive parity bit */
+  serial_delay_half1();   // read the middle of pulses
+  pb = serial_read_pin();
+  _delay_sub_us(READ_WRITE_WIDTH_ADJUST);
+  serial_delay_half2();
+
+  *pterrcount += (p != pb)? 1 : 0;
+
+  return byte;
+}
+
+// Sends a byte with MSB ordering
+void serial_write_chunk(uint8_t data, uint8_t bit) NO_INLINE;
+void serial_write_chunk(uint8_t data, uint8_t bit) {
+    uint8_t b, p;
+    for( p = PARITY, b = 1<<(bit-1); b ; b >>= 1) {
+        if(data & b) {
+            serial_high(); p ^= 1;
+        } else {
+            serial_low();  p ^= 0;
+        }
+        serial_delay();
+    }
+    /* send parity bit */
+    if(p & 1) { serial_high(); }
+    else      { serial_low(); }
+    serial_delay();
+
+    serial_low(); // sync_send() / senc_recv() need raise edge
+}
+
+static void serial_send_packet(uint8_t *buffer, uint8_t size) NO_INLINE;
+static
+void serial_send_packet(uint8_t *buffer, uint8_t size) {
+  for (uint8_t i = 0; i < size; ++i) {
+    uint8_t data;
+    data = buffer[i];
+    sync_send();
+    serial_write_chunk(data,8);
+  }
+}
+
+static uint8_t serial_recive_packet(uint8_t *buffer, uint8_t size) NO_INLINE;
+static
+uint8_t serial_recive_packet(uint8_t *buffer, uint8_t size) {
+  uint8_t pecount = 0;
+  for (uint8_t i = 0; i < size; ++i) {
+    uint8_t data;
+    sync_recv();
+    data = serial_read_chunk(&pecount, 8);
+    buffer[i] = data;
+  }
+  return pecount == 0;
+}
+
+inline static
+void change_sender2reciver(void) {
+    sync_send();          //0
+    serial_delay_half1(); //1
+    serial_low();         //2
+    serial_input_with_pullup(); //2
+    serial_delay_half1(); //3
+}
+
+inline static
+void change_reciver2sender(void) {
+    sync_recv();     //0
+    serial_delay();  //1
+    serial_low();    //3
+    serial_output(); //3
+    serial_delay_half1(); //4
+}
+
+static inline uint8_t nibble_bits_count(uint8_t bits)
+{
+    bits = (bits & 0x5) + (bits >> 1 & 0x5);
+    bits = (bits & 0x3) + (bits >> 2 & 0x3);
+    return bits;
+}
+
+// interrupt handle to be used by the target device
+ISR(SERIAL_PIN_INTERRUPT) {
+
+#ifndef SERIAL_USE_MULTI_TRANSACTION
+  serial_low();
+  serial_output();
+  SSTD_t *trans = Transaction_table;
+#else
+  // recive transaction table index
+  uint8_t tid, bits;
+  uint8_t pecount = 0;
+  sync_recv();
+  bits = serial_read_chunk(&pecount,7);
+  tid = bits>>3;
+  bits = (bits&7) != nibble_bits_count(tid);
+  if( bits || pecount> 0 || tid > Transaction_table_size ) {
+      return;
+  }
+  serial_delay_half1();
+
+  serial_high(); // response step1 low->high
+  serial_output();
+  _delay_sub_us(SLAVE_INT_ACK_WIDTH_UNIT*SLAVE_INT_ACK_WIDTH);
+  SSTD_t *trans = &Transaction_table[tid];
+  serial_low(); // response step2 ack high->low
+#endif
+
+  // target send phase
+  if( trans->target2initiator_buffer_size > 0 )
+      serial_send_packet((uint8_t *)trans->target2initiator_buffer,
+                         trans->target2initiator_buffer_size);
+  // target switch to input
+  change_sender2reciver();
+
+  // target recive phase
+  if( trans->initiator2target_buffer_size > 0 ) {
+      if (serial_recive_packet((uint8_t *)trans->initiator2target_buffer,
+                               trans->initiator2target_buffer_size) ) {
+          *trans->status = TRANSACTION_ACCEPTED;
+      } else {
+          *trans->status = TRANSACTION_DATA_ERROR;
+      }
+  } else {
+      *trans->status = TRANSACTION_ACCEPTED;
+  }
+
+  sync_recv(); //weit initiator output to high
+}
+
+/////////
+//  start transaction by initiator
+//
+// int  soft_serial_transaction(int sstd_index)
+//
+// Returns:
+//    TRANSACTION_END
+//    TRANSACTION_NO_RESPONSE
+//    TRANSACTION_DATA_ERROR
+// this code is very time dependent, so we need to disable interrupts
+#ifndef SERIAL_USE_MULTI_TRANSACTION
+int  soft_serial_transaction(void) {
+  SSTD_t *trans = Transaction_table;
+#else
+int  soft_serial_transaction(int sstd_index) {
+  if( sstd_index > Transaction_table_size )
+      return TRANSACTION_TYPE_ERROR;
+  SSTD_t *trans = &Transaction_table[sstd_index];
+#endif
+  cli();
+
+  // signal to the target that we want to start a transaction
+  serial_output();
+  serial_low();
+  _delay_us(SLAVE_INT_WIDTH_US);
+
+#ifndef SERIAL_USE_MULTI_TRANSACTION
+  // wait for the target response
+  serial_input_with_pullup();
+  _delay_us(SLAVE_INT_RESPONSE_TIME);
+
+  // check if the target is present
+  if (serial_read_pin()) {
+    // target failed to pull the line low, assume not present
+    serial_output();
+    serial_high();
+    *trans->status = TRANSACTION_NO_RESPONSE;
+    sei();
+    return TRANSACTION_NO_RESPONSE;
+  }
+
+#else
+  // send transaction table index
+  int tid = (sstd_index<<3) | (7 & nibble_bits_count(sstd_index));
+  sync_send();
+  _delay_sub_us(TID_SEND_ADJUST);
+  serial_write_chunk(tid, 7);
+  serial_delay_half1();
+
+  // wait for the target response (step1 low->high)
+  serial_input_with_pullup();
+  while( !serial_read_pin() ) {
+      _delay_sub_us(2);
+  }
+
+  // check if the target is present (step2 high->low)
+  for( int i = 0; serial_read_pin(); i++ ) {
+      if (i > SLAVE_INT_ACK_WIDTH + 1) {
+          // slave failed to pull the line low, assume not present
+          serial_output();
+          serial_high();
+          *trans->status = TRANSACTION_NO_RESPONSE;
+          sei();
+          return TRANSACTION_NO_RESPONSE;
+      }
+      _delay_sub_us(SLAVE_INT_ACK_WIDTH_UNIT);
+  }
+#endif
+
+  // initiator recive phase
+  // if the target is present syncronize with it
+  if( trans->target2initiator_buffer_size > 0 ) {
+      if (!serial_recive_packet((uint8_t *)trans->target2initiator_buffer,
+                                trans->target2initiator_buffer_size) ) {
+          serial_output();
+          serial_high();
+          *trans->status = TRANSACTION_DATA_ERROR;
+          sei();
+          return TRANSACTION_DATA_ERROR;
+      }
+   }
+
+  // initiator switch to output
+  change_reciver2sender();
+
+  // initiator send phase
+  if( trans->initiator2target_buffer_size > 0 ) {
+      serial_send_packet((uint8_t *)trans->initiator2target_buffer,
+                         trans->initiator2target_buffer_size);
+  }
+
+  // always, release the line when not in use
+  sync_send();
+
+  *trans->status = TRANSACTION_END;
+  sei();
+  return TRANSACTION_END;
+}
+
+#ifdef SERIAL_USE_MULTI_TRANSACTION
+int soft_serial_get_and_clean_status(int sstd_index) {
+    SSTD_t *trans = &Transaction_table[sstd_index];
+    cli();
+    int retval = *trans->status;
+    *trans->status = 0;;
+    sei();
+    return retval;
+}
+#endif
+
+#endif
+
+// Helix serial.c history
+//   2018-1-29 fork from let's split and add PD2, modify sync_recv() (#2308, bceffdefc)
+//   2018-6-28 bug fix master to slave comm and speed up (#3255, 1038bbef4)
+//             (adjusted with avr-gcc 4.9.2)
+//   2018-7-13 remove USE_SERIAL_PD2 macro (#3374, f30d6dd78)
+//             (adjusted with avr-gcc 4.9.2)
+//   2018-8-11 add support multi-type transaction (#3608, feb5e4aae)
+//             (adjusted with avr-gcc 4.9.2)
+//   2018-10-21 fix serial and RGB animation conflict (#4191, 4665e4fff)
+//             (adjusted with avr-gcc 7.3.0)
+//   2018-10-28 re-adjust compiler depend value of delay (#4269, 8517f8a66)
+//             (adjusted with avr-gcc 5.4.0, 7.3.0)
diff --git a/keyboards/crkbd/rev1/legacy/serial.h b/keyboards/crkbd/rev1/legacy/serial.h
new file mode 100644
index 0000000000..7e0c0847a4
--- /dev/null
+++ b/keyboards/crkbd/rev1/legacy/serial.h
@@ -0,0 +1,84 @@
+#ifndef SOFT_SERIAL_H
+#define SOFT_SERIAL_H
+
+#include <stdbool.h>
+
+// /////////////////////////////////////////////////////////////////
+// Need Soft Serial defines in config.h
+// /////////////////////////////////////////////////////////////////
+// ex.
+//  #define SOFT_SERIAL_PIN ??   // ?? = D0,D1,D2,D3,E6
+//  OPTIONAL: #define SELECT_SOFT_SERIAL_SPEED ? // ? = 1,2,3,4,5
+//                                               //  1: about 137kbps (default)
+//                                               //  2: about 75kbps
+//                                               //  3: about 39kbps
+//                                               //  4: about 26kbps
+//                                               //  5: about 20kbps
+//
+// //// USE Simple API (OLD API, compatible with let's split serial.c)
+// ex.
+//  #define SERIAL_SLAVE_BUFFER_LENGTH MATRIX_ROWS/2
+//  #define SERIAL_MASTER_BUFFER_LENGTH 1
+//
+// //// USE flexible API (using multi-type transaction function)
+//  #define SERIAL_USE_MULTI_TRANSACTION
+//
+// /////////////////////////////////////////////////////////////////
+
+
+#ifndef SERIAL_USE_MULTI_TRANSACTION
+/* --- USE Simple API (OLD API, compatible with let's split serial.c) */
+#if SERIAL_SLAVE_BUFFER_LENGTH > 0
+extern volatile uint8_t serial_slave_buffer[SERIAL_SLAVE_BUFFER_LENGTH];
+#endif
+#if SERIAL_MASTER_BUFFER_LENGTH > 0
+extern volatile uint8_t serial_master_buffer[SERIAL_MASTER_BUFFER_LENGTH];
+#endif
+
+void serial_master_init(void);
+void serial_slave_init(void);
+int serial_update_buffers(void);
+
+#endif // USE Simple API
+
+// Soft Serial Transaction Descriptor
+typedef struct _SSTD_t  {
+    uint8_t *status;
+    uint8_t initiator2target_buffer_size;
+    uint8_t *initiator2target_buffer;
+    uint8_t target2initiator_buffer_size;
+    uint8_t *target2initiator_buffer;
+} SSTD_t;
+#define TID_LIMIT( table ) (sizeof(table) / sizeof(SSTD_t))
+
+// initiator is transaction start side
+void soft_serial_initiator_init(SSTD_t *sstd_table, int sstd_table_size);
+// target is interrupt accept side
+void soft_serial_target_init(SSTD_t *sstd_table, int sstd_table_size);
+
+// initiator resullt
+#define TRANSACTION_END 0
+#define TRANSACTION_NO_RESPONSE 0x1
+#define TRANSACTION_DATA_ERROR  0x2
+#define TRANSACTION_TYPE_ERROR  0x4
+#ifndef SERIAL_USE_MULTI_TRANSACTION
+int  soft_serial_transaction(void);
+#else
+int  soft_serial_transaction(int sstd_index);
+#endif
+
+// target status
+// *SSTD_t.status has
+//   initiator:
+//       TRANSACTION_END
+//    or TRANSACTION_NO_RESPONSE
+//    or TRANSACTION_DATA_ERROR
+//   target:
+//       TRANSACTION_DATA_ERROR
+//    or TRANSACTION_ACCEPTED
+#define TRANSACTION_ACCEPTED 0x8
+#ifdef SERIAL_USE_MULTI_TRANSACTION
+int  soft_serial_get_and_clean_status(int sstd_index);
+#endif
+
+#endif /* SOFT_SERIAL_H */
diff --git a/keyboards/crkbd/rev1/legacy/serial_config.h b/keyboards/crkbd/rev1/legacy/serial_config.h
new file mode 100644
index 0000000000..40d11d4de2
--- /dev/null
+++ b/keyboards/crkbd/rev1/legacy/serial_config.h
@@ -0,0 +1,22 @@
+/*
+Copyright 2019 @foostan
+Copyright 2020 Drashna Jaelre <@drashna>
+
+This program is free software: you can redistribute it and/or modify
+it under the terms of the GNU General Public License as published by
+the Free Software Foundation, either version 2 of the License, or
+(at your option) any later version.
+
+This program is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+GNU General Public License for more details.
+
+You should have received a copy of the GNU General Public License
+along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+#ifndef SOFT_SERIAL_PIN
+#define SOFT_SERIAL_PIN D2
+#define SERIAL_USE_MULTI_TRANSACTION
+#endif
diff --git a/keyboards/crkbd/rev1/legacy/serial_config_simpleapi.h b/keyboards/crkbd/rev1/legacy/serial_config_simpleapi.h
new file mode 100644
index 0000000000..bd152ddda3
--- /dev/null
+++ b/keyboards/crkbd/rev1/legacy/serial_config_simpleapi.h
@@ -0,0 +1,23 @@
+/*
+Copyright 2019 @foostan
+Copyright 2020 Drashna Jaelre <@drashna>
+
+This program is free software: you can redistribute it and/or modify
+it under the terms of the GNU General Public License as published by
+the Free Software Foundation, either version 2 of the License, or
+(at your option) any later version.
+
+This program is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+GNU General Public License for more details.
+
+You should have received a copy of the GNU General Public License
+along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+#pragma once
+
+#undef SERIAL_USE_MULTI_TRANSACTION
+#define SERIAL_SLAVE_BUFFER_LENGTH MATRIX_ROWS/2
+#define SERIAL_MASTER_BUFFER_LENGTH MATRIX_ROWS/2
diff --git a/keyboards/crkbd/rev1/legacy/split_scomm.c b/keyboards/crkbd/rev1/legacy/split_scomm.c
new file mode 100644
index 0000000000..c14bb32a43
--- /dev/null
+++ b/keyboards/crkbd/rev1/legacy/split_scomm.c
@@ -0,0 +1,111 @@
+/*
+Copyright 2019 @foostan
+Copyright 2020 Drashna Jaelre <@drashna>
+
+This program is free software: you can redistribute it and/or modify
+it under the terms of the GNU General Public License as published by
+the Free Software Foundation, either version 2 of the License, or
+(at your option) any later version.
+
+This program is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+GNU General Public License for more details.
+
+You should have received a copy of the GNU General Public License
+along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+#ifdef USE_SERIAL
+#ifdef SERIAL_USE_MULTI_TRANSACTION
+/* --- USE flexible API (using multi-type transaction function) --- */
+
+#include <stdbool.h>
+#include <stdint.h>
+#include <stddef.h>
+#include <split_scomm.h>
+#include "serial.h"
+#ifdef CONSOLE_ENABLE
+  #include "debug.h"
+#endif
+
+uint8_t volatile serial_slave_buffer[SERIAL_SLAVE_BUFFER_LENGTH] = {0};
+uint8_t volatile serial_master_buffer[SERIAL_MASTER_BUFFER_LENGTH] = {0};
+uint8_t volatile status_com = 0;
+uint8_t volatile status1 = 0;
+uint8_t slave_buffer_change_count = 0;
+uint8_t s_change_old = 0xff;
+uint8_t s_change_new = 0xff;
+
+SSTD_t transactions[] = {
+#define GET_SLAVE_STATUS 0
+    /* master buffer not changed, only recive slave_buffer_change_count */
+    { (uint8_t *)&status_com,
+      0, NULL,
+      sizeof(slave_buffer_change_count), &slave_buffer_change_count,
+    },
+#define PUT_MASTER_GET_SLAVE_STATUS 1
+    /* master buffer changed need send, and recive slave_buffer_change_count  */
+    { (uint8_t *)&status_com,
+      sizeof(serial_master_buffer), (uint8_t *)serial_master_buffer,
+      sizeof(slave_buffer_change_count), &slave_buffer_change_count,
+    },
+#define GET_SLAVE_BUFFER 2
+    /* recive serial_slave_buffer */
+    { (uint8_t *)&status1,
+      0, NULL,
+      sizeof(serial_slave_buffer), (uint8_t *)serial_slave_buffer
+    }
+};
+
+void serial_master_init(void)
+{
+    soft_serial_initiator_init(transactions, TID_LIMIT(transactions));
+}
+
+void serial_slave_init(void)
+{
+    soft_serial_target_init(transactions, TID_LIMIT(transactions));
+}
+
+// 0 => no error
+// 1 => slave did not respond
+// 2 => checksum error
+int serial_update_buffers(int master_update)
+{
+    int status, smatstatus;
+    static int need_retry = 0;
+
+    if( s_change_old != s_change_new ) {
+        smatstatus = soft_serial_transaction(GET_SLAVE_BUFFER);
+        if( smatstatus == TRANSACTION_END ) {
+            s_change_old = s_change_new;
+#ifdef CONSOLE_ENABLE
+            if (debug_matrix) {
+                uprintf("slave matrix = %b %b %b %b\n",
+                    serial_slave_buffer[0], serial_slave_buffer[1],
+                    serial_slave_buffer[2], serial_slave_buffer[3]);
+            }
+#endif
+        }
+    } else {
+        // serial_slave_buffer dosen't change
+        smatstatus = TRANSACTION_END; // dummy status
+    }
+
+    if( !master_update && !need_retry) {
+        status = soft_serial_transaction(GET_SLAVE_STATUS);
+    } else {
+        status = soft_serial_transaction(PUT_MASTER_GET_SLAVE_STATUS);
+    }
+    if( status == TRANSACTION_END ) {
+        s_change_new = slave_buffer_change_count;
+        need_retry = 0;
+    } else {
+        need_retry = 1;
+    }
+    return smatstatus;
+}
+
+#endif // SERIAL_USE_MULTI_TRANSACTION
+#endif /* USE_SERIAL */
diff --git a/keyboards/crkbd/rev1/legacy/split_scomm.h b/keyboards/crkbd/rev1/legacy/split_scomm.h
new file mode 100644
index 0000000000..47f0ca1b9d
--- /dev/null
+++ b/keyboards/crkbd/rev1/legacy/split_scomm.h
@@ -0,0 +1,42 @@
+/*
+Copyright 2019 @foostan
+Copyright 2020 Drashna Jaelre <@drashna>
+
+This program is free software: you can redistribute it and/or modify
+it under the terms of the GNU General Public License as published by
+the Free Software Foundation, either version 2 of the License, or
+(at your option) any later version.
+
+This program is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+GNU General Public License for more details.
+
+You should have received a copy of the GNU General Public License
+along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+#ifndef SPLIT_COMM_H
+#define SPLIT_COMM_H
+
+#ifndef SERIAL_USE_MULTI_TRANSACTION
+/* --- USE Simple API (OLD API, compatible with let's split serial.c) --- */
+#include "serial.h"
+
+#else
+/* --- USE flexible API (using multi-type transaction function) --- */
+// Buffers for master - slave communication
+#define SERIAL_SLAVE_BUFFER_LENGTH MATRIX_ROWS/2
+#define SERIAL_MASTER_BUFFER_LENGTH MATRIX_ROWS/2
+
+extern volatile uint8_t serial_slave_buffer[SERIAL_SLAVE_BUFFER_LENGTH];
+extern volatile uint8_t serial_master_buffer[SERIAL_MASTER_BUFFER_LENGTH];
+extern uint8_t slave_buffer_change_count;
+
+void serial_master_init(void);
+void serial_slave_init(void);
+int serial_update_buffers(int master_changed);
+
+#endif
+
+#endif /* SPLIT_COMM_H */
diff --git a/keyboards/crkbd/rev1/legacy/split_util.c b/keyboards/crkbd/rev1/legacy/split_util.c
new file mode 100644
index 0000000000..d0fee04ad6
--- /dev/null
+++ b/keyboards/crkbd/rev1/legacy/split_util.c
@@ -0,0 +1,127 @@
+/*
+Copyright 2019 @foostan
+Copyright 2020 Drashna Jaelre <@drashna>
+
+This program is free software: you can redistribute it and/or modify
+it under the terms of the GNU General Public License as published by
+the Free Software Foundation, either version 2 of the License, or
+(at your option) any later version.
+
+This program is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+GNU General Public License for more details.
+
+You should have received a copy of the GNU General Public License
+along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+#include <avr/io.h>
+#include <avr/wdt.h>
+#include <avr/power.h>
+#include <avr/interrupt.h>
+#include <util/delay.h>
+#include <avr/eeprom.h>
+#include "split_util.h"
+#include "matrix.h"
+#include "keyboard.h"
+#include "wait.h"
+
+#ifdef EE_HANDS
+#    include "eeconfig.h"
+#endif
+
+#ifdef USE_MATRIX_I2C
+#  include "i2c_master.h"
+#else
+#  include "split_scomm.h"
+#endif
+
+#ifndef SPLIT_USB_TIMEOUT
+#    define SPLIT_USB_TIMEOUT 2000
+#endif
+
+#ifndef SPLIT_USB_TIMEOUT_POLL
+#    define SPLIT_USB_TIMEOUT_POLL 10
+#endif
+
+volatile bool isLeftHand = true;
+
+bool waitForUsb(void) {
+    for (uint8_t i = 0; i < (SPLIT_USB_TIMEOUT / SPLIT_USB_TIMEOUT_POLL); i++) {
+        // This will return true if a USB connection has been established
+        if (UDADDR & _BV(ADDEN)) {
+            return true;
+        }
+        wait_ms(SPLIT_USB_TIMEOUT_POLL);
+    }
+
+    // Avoid NO_USB_STARTUP_CHECK - Disable USB as the previous checks seem to enable it somehow
+    (USBCON &= ~(_BV(USBE) | _BV(OTGPADE)));
+
+    return false;
+}
+
+__attribute__((weak)) bool is_keyboard_left(void) {
+#if defined(SPLIT_HAND_PIN)
+    // Test pin SPLIT_HAND_PIN for High/Low, if low it's right hand
+    setPinInput(SPLIT_HAND_PIN);
+    return readPin(SPLIT_HAND_PIN);
+#elif defined(EE_HANDS)
+    return eeconfig_read_handedness();
+#elif defined(MASTER_RIGHT)
+    return !has_usb();
+#endif
+
+    return has_usb();
+}
+
+__attribute__((weak)) bool has_usb(void) {
+    static enum { UNKNOWN, MASTER, SLAVE } usbstate = UNKNOWN;
+
+    // only check once, as this is called often
+    if (usbstate == UNKNOWN) {
+#if defined(SPLIT_USB_DETECT)
+        usbstate = waitForUsb() ? MASTER : SLAVE;
+#elif defined(__AVR__)
+        USBCON |= (1 << OTGPADE);  // enables VBUS pad
+        wait_us(5);
+
+        usbstate = (USBSTA & (1 << VBUS)) ? MASTER : SLAVE;  // checks state of VBUS
+#else
+        usbstate = MASTER;
+#endif
+    }
+
+    return (usbstate == MASTER);
+}
+
+static void keyboard_master_setup(void) {
+
+#ifdef USE_MATRIX_I2C
+    i2c_init();
+#else
+    serial_master_init();
+#endif
+}
+
+static void keyboard_slave_setup(void) {
+
+#ifdef USE_MATRIX_I2C
+    i2c_slave_init(SLAVE_I2C_ADDRESS);
+#else
+    serial_slave_init();
+#endif
+}
+
+// this code runs before the usb and keyboard is initialized
+void split_keyboard_setup(void) {
+    isLeftHand = is_keyboard_left();
+
+   if (has_usb()) {
+      keyboard_master_setup();
+   } else {
+      keyboard_slave_setup();
+   }
+   sei();
+}
diff --git a/keyboards/crkbd/rev1/legacy/split_util.h b/keyboards/crkbd/rev1/legacy/split_util.h
new file mode 100644
index 0000000000..414763bff2
--- /dev/null
+++ b/keyboards/crkbd/rev1/legacy/split_util.h
@@ -0,0 +1,37 @@
+/*
+Copyright 2019 @foostan
+Copyright 2020 Drashna Jaelre <@drashna>
+
+This program is free software: you can redistribute it and/or modify
+it under the terms of the GNU General Public License as published by
+the Free Software Foundation, either version 2 of the License, or
+(at your option) any later version.
+
+This program is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+GNU General Public License for more details.
+
+You should have received a copy of the GNU General Public License
+along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+#ifndef SPLIT_KEYBOARD_UTIL_H
+#define SPLIT_KEYBOARD_UTIL_H
+
+#include <stdbool.h>
+#include "eeconfig.h"
+
+#define SLAVE_I2C_ADDRESS           0x32
+
+extern volatile bool isLeftHand;
+
+// slave version of matix scan, defined in matrix.c
+void matrix_slave_scan(void);
+
+void split_keyboard_setup(void);
+bool has_usb(void);
+
+void matrix_master_OLED_init (void);
+
+#endif
diff --git a/keyboards/crkbd/rev1/legacy/ssd1306.c b/keyboards/crkbd/rev1/legacy/ssd1306.c
new file mode 100644
index 0000000000..b04b7e15c1
--- /dev/null
+++ b/keyboards/crkbd/rev1/legacy/ssd1306.c
@@ -0,0 +1,357 @@
+#ifdef SSD1306OLED
+
+#include "ssd1306.h"
+#include "i2c.h"
+#include <string.h>
+#include "print.h"
+#ifdef PROTOCOL_LUFA
+#include "lufa.h"
+#endif
+#include "sendchar.h"
+#include "timer.h"
+
+struct CharacterMatrix display;
+
+extern const unsigned char font[] PROGMEM;
+
+#ifndef OLED_BLANK_CHAR
+#define OLED_BLANK_CHAR ' '
+#endif
+
+#ifndef OLED_BITS_FILTER
+#define OLED_BITS_FILTER
+#endif
+
+// Set this to 1 to help diagnose early startup problems
+// when testing power-on with ble.  Turn it off otherwise,
+// as the latency of printing most of the debug info messes
+// with the matrix scan, causing keys to drop.
+#define DEBUG_TO_SCREEN 0
+
+//static uint16_t last_battery_update;
+//static uint32_t vbat;
+//#define BatteryUpdateInterval 10000 /* milliseconds */
+
+// 'last_flush' is declared as uint16_t,
+// so this must be less than 65535
+#ifndef ScreenOffInterval
+#define ScreenOffInterval 60000 /* milliseconds */
+#endif
+
+#if DEBUG_TO_SCREEN
+static uint8_t displaying;
+#endif
+static uint16_t last_flush;
+
+static bool force_dirty = true;
+
+// Write command sequence.
+// Returns true on success.
+static inline bool _send_cmd1(uint8_t cmd) {
+  bool res = false;
+
+  if (i2c_start_write(SSD1306_ADDRESS)) {
+    xprintf("failed to start write to %d\n", SSD1306_ADDRESS);
+    goto done;
+  }
+
+  if (i2c_master_write(0x0 /* command byte follows */)) {
+    print("failed to write control byte\n");
+
+    goto done;
+  }
+
+  if (i2c_master_write(cmd)) {
+    xprintf("failed to write command %d\n", cmd);
+    goto done;
+  }
+  res = true;
+done:
+  i2c_master_stop();
+  return res;
+}
+
+#define send_cmd1(c) if (!_send_cmd1(c)) {goto done;}
+#define send_cmds(c) if (!_send_cmds(c,sizeof(c))) {goto done;}
+#define cmd1(X) X
+#define cmd2(X,Y) X,Y
+#define cmd3(X,Y,Z) X,Y,Z
+
+static bool _send_cmds(const uint8_t* p,uint8_t sz) {
+  for(uint8_t i=sz;i;i--) {
+    send_cmd1( pgm_read_byte(p++) );
+  }
+  return true;
+done:
+  return false;
+}
+
+#define SEND_CMDS(...) {static const uint8_t _cmds[] PROGMEM = { __VA_ARGS__,0 };send_cmds(_cmds);}
+
+static void clear_display(void) {
+  matrix_clear(&display);
+
+  // Clear all of the display bits (there can be random noise
+  // in the RAM on startup)
+  SEND_CMDS(
+    cmd3(PageAddr, 0, (DisplayHeight / 8) - 1),
+    cmd3(ColumnAddr, 0, DisplayWidth - 1)
+  );
+
+  if (i2c_start_write(SSD1306_ADDRESS)) {
+    goto done;
+  }
+  if (i2c_master_write(0x40)) {
+    // Data mode
+    goto done;
+  }
+  for (uint8_t row = MatrixRows;row; row--) {
+    for (uint8_t col = DisplayWidth; col; col--) {
+      i2c_master_write(0);
+    }
+  }
+
+  display.dirty = false;
+
+done:
+  i2c_master_stop();
+}
+
+#if DEBUG_TO_SCREEN
+#undef sendchar
+static int8_t capture_sendchar(uint8_t c) {
+  sendchar(c);
+  iota_gfx_write_char(c);
+
+  if (!displaying) {
+    iota_gfx_flush();
+  }
+  return 0;
+}
+#endif
+
+bool iota_gfx_init(bool rotate) {
+  bool success = false;
+
+  i2c_master_init();
+  SEND_CMDS(
+    cmd1(DisplayOff),
+    cmd2(SetDisplayClockDiv, 0x80),
+    cmd2(SetMultiPlex, DisplayHeight - 1),
+    cmd2(SetDisplayOffset, 0),
+    cmd1(SetStartLine | 0x0),
+    cmd2(SetChargePump, 0x14 /* Enable */),
+    cmd2(SetMemoryMode, 0 /* horizontal addressing */)
+  );
+
+  if(rotate){
+    // the following Flip the display orientation 180 degrees
+  SEND_CMDS(
+    cmd1(SegRemap),
+    cmd1(ComScanInc)
+  );
+  }else{
+    // Flips the display orientation 0 degrees
+  SEND_CMDS(
+      cmd1(SegRemap | 0x1),
+      cmd1(ComScanDec)
+    );
+  }
+
+  SEND_CMDS(
+#ifdef SSD1306_128X64
+	cmd2(SetComPins, 0x12),
+#else
+	cmd2(SetComPins, 0x2),
+#endif
+    cmd2(SetContrast, 0x8f),
+    cmd2(SetPreCharge, 0xf1),
+    cmd2(SetVComDetect, 0x40),
+    cmd1(DisplayAllOnResume),
+    cmd1(NormalDisplay),
+    cmd1(DeActivateScroll),
+    cmd1(DisplayOn),
+
+    cmd2(SetContrast, 0) // Dim
+  );
+
+  clear_display();
+
+  success = true;
+
+  iota_gfx_flush();
+
+#if DEBUG_TO_SCREEN
+  print_set_sendchar(capture_sendchar);
+#endif
+
+done:
+  return success;
+}
+
+bool iota_gfx_off(void) {
+  bool success = false;
+
+  send_cmd1(DisplayOff);
+  success = true;
+
+done:
+  return success;
+}
+
+bool iota_gfx_on(void) {
+  bool success = false;
+
+  send_cmd1(DisplayOn);
+  success = true;
+
+done:
+  return success;
+}
+
+void matrix_write_char_inner(struct CharacterMatrix *matrix, uint8_t c) {
+  *matrix->cursor = c;
+  ++matrix->cursor;
+
+  if (matrix->cursor - &matrix->display[0][0] == sizeof(matrix->display)) {
+    // We went off the end; scroll the display upwards by one line
+    memmove(&matrix->display[0], &matrix->display[1],
+            MatrixCols * (MatrixRows - 1));
+    matrix->cursor = &matrix->display[MatrixRows - 1][0];
+    memset(matrix->cursor, OLED_BLANK_CHAR, MatrixCols);
+  }
+}
+
+void matrix_write_char(struct CharacterMatrix *matrix, uint8_t c) {
+  matrix->dirty = true;
+
+  if (c == '\n') {
+    // Clear to end of line from the cursor and then move to the
+    // start of the next line
+    uint8_t cursor_col = (matrix->cursor - &matrix->display[0][0]) % MatrixCols;
+
+    while (cursor_col++ < MatrixCols) {
+      matrix_write_char_inner(matrix, OLED_BLANK_CHAR);
+    }
+    return;
+  }
+
+  matrix_write_char_inner(matrix, c);
+}
+
+void iota_gfx_write_char(uint8_t c) {
+  matrix_write_char(&display, c);
+}
+
+void matrix_write(struct CharacterMatrix *matrix, const char *data) {
+  while (*data) {
+    matrix_write_char(matrix, *data);
+    ++data;
+  }
+}
+
+void matrix_write_ln(struct CharacterMatrix *matrix, const char *data) {
+  matrix_write(matrix, data);
+  matrix_write(matrix, "\n");
+}
+
+void iota_gfx_write(const char *data) {
+  matrix_write(&display, data);
+}
+
+void matrix_write_P(struct CharacterMatrix *matrix, const char *data) {
+  while (true) {
+    uint8_t c = pgm_read_byte(data);
+    if (c == 0) {
+      return;
+    }
+    matrix_write_char(matrix, c);
+    ++data;
+  }
+}
+
+void iota_gfx_write_P(const char *data) {
+  matrix_write_P(&display, data);
+}
+
+void matrix_clear(struct CharacterMatrix *matrix) {
+  memset(matrix->display, OLED_BLANK_CHAR, sizeof(matrix->display));
+  matrix->cursor = &matrix->display[0][0];
+  matrix->dirty = true;
+}
+
+void iota_gfx_clear_screen(void) {
+  matrix_clear(&display);
+}
+
+void matrix_render(struct CharacterMatrix *matrix) {
+  last_flush = timer_read();
+  iota_gfx_on();
+#if DEBUG_TO_SCREEN
+  ++displaying;
+#endif
+
+  // Move to the home position
+  SEND_CMDS(
+    cmd3(PageAddr, 0, MatrixRows - 1),
+    cmd3(ColumnAddr, 0, (MatrixCols * FontWidth) - 1)
+  );
+
+  if (i2c_start_write(SSD1306_ADDRESS)) {
+    goto done;
+  }
+  if (i2c_master_write(0x40)) {
+    // Data mode
+    goto done;
+  }
+
+  for (uint8_t row = 0; row < MatrixRows; ++row) {
+    for (uint8_t col = 0; col < MatrixCols; ++col) {
+      const uint8_t *glyph = font + (matrix->display[row][col] * FontWidth);
+
+      for (uint8_t glyphCol = 0; glyphCol < FontWidth; ++glyphCol) {
+        uint8_t colBits = pgm_read_byte(glyph + glyphCol);
+        i2c_master_write(colBits OLED_BITS_FILTER);
+      }
+
+      // 1 column of space between chars (it's not included in the glyph)
+      //i2c_master_write(0);
+    }
+  }
+
+  matrix->dirty = false;
+
+done:
+  i2c_master_stop();
+#if DEBUG_TO_SCREEN
+  --displaying;
+#endif
+}
+
+void iota_gfx_flush(void) {
+  matrix_render(&display);
+}
+
+__attribute__ ((weak))
+void iota_gfx_task_user(void) {
+}
+
+void iota_gfx_task(void) {
+  iota_gfx_task_user();
+
+  if (display.dirty|| force_dirty) {
+    iota_gfx_flush();
+    force_dirty = false;
+  }
+
+  if (ScreenOffInterval !=0 && timer_elapsed(last_flush) > ScreenOffInterval) {
+    iota_gfx_off();
+  }
+}
+
+bool process_record_gfx(uint16_t keycode, keyrecord_t *record) {
+  force_dirty = true;
+  return true;
+}
+
+#endif