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/*
Copyright 2010,2011,2012,2013 Jun WAKO <wakojun@gmail.com>
*/
#include <stdbool.h>
#include <util/delay.h>
#include "debug.h"
#include "ibm4704.h"
#define WAIT(stat, us, err) do { \
if (!wait_##stat(us)) { \
ibm4704_error = err; \
goto ERROR; \
} \
} while (0)
uint8_t ibm4704_error = 0;
void ibm4704_init(void)
{
inhibit();
}
/*
Host to Keyboard
----------------
Data bits are LSB first and Parity is odd. Clock has around 60us high and 30us low part.
____ __ __ __ __ __ __ __ __ __ ________
Clock \______/ \_/ \_/ \_/ \_/ \_/ \_/ \_/ \_/ \_/
^ ____ ____ ____ ____ ____ ____ ____ ____ ____ ____ ___
Data ____|__/ X____X____X____X____X____X____X____X____X____X \___
| Start 0 1 2 3 4 5 6 7 P Stop
Request by host
Start bit: can be long as 300-350us.
Request: Host pulls Clock line down to request to send a command.
Timing: After Request keyboard pull up Data and down Clock line to low for start bit.
After request host release Clock line once Data line becomes hi.
Host writes a bit while Clock is hi and Keyboard reads while low.
Stop bit: Host releases or pulls up Data line to hi after 9th clock and waits for keyboard pull down the line to lo.
*/
uint8_t ibm4704_send(uint8_t data)
{
bool parity = true; // odd parity
ibm4704_error = 0;
/* Request to send */
idle();
clock_lo();
/* wait for Start bit(Clock:lo/Data:hi) */
WAIT(data_hi, 300, 0x30);
/* Data bit */
for (uint8_t i = 0; i < 8; i++) {
WAIT(clock_hi, 100, 0x40+i);
//_delay_us(5);
if (data&(1<<i)) {
parity = !parity;
data_hi();
} else {
data_lo();
}
WAIT(clock_lo, 100, 0x48+i);
}
/* Parity bit */
WAIT(clock_hi, 100, 0x34);
if (parity) { data_hi(); } else { data_lo(); }
WAIT(clock_lo, 100, 0x35);
/* Stop bit */
WAIT(clock_hi, 100, 0x34);
data_hi();
/* End */
WAIT(data_lo, 100, 0x36);
inhibit();
_delay_us(200); // wait to recover clock to hi
return 0;
ERROR:
inhibit();
if (ibm4704_error >= 0x30) {
xprintf("x%02X ", ibm4704_error);
}
_delay_us(200); // wait to recover clock to hi
return -1;
}
/* receive data when host want else inhibit communication */
uint8_t ibm4704_recv_response(void)
{
// 250 * 100us(wait start bit in ibm4704_recv)
uint8_t data = 0;
uint8_t try = 250;
do {
data = ibm4704_recv();
} while (try-- && ibm4704_error);
return data;
}
/*
Keyboard to Host
----------------
Data bits are LSB first and Parity is odd. Clock has around 60us high and 30us low part.
____ __ __ __ __ __ __ __ __ __ ________
Clock \____/ \_/ \_/ \_/ \_/ \_/ \_/ \_/ \_/ \_/
____ ____ ____ ____ ____ ____ ____ ____ ____ ____
Data ____/ X____X____X____X____X____X____X____X____X____X________
Start 0 1 2 3 4 5 6 7 P Stop
Start bit: can be long as 300-350us.
Inhibit: Pull Data line down to inhibit keyboard to send.
Timing: Host reads bit while Clock is hi.
Stop bit: Keyboard pulls down Data line to lo after 9th clock.
*/
uint8_t ibm4704_recv(void)
{
uint8_t data = 0;
bool parity = true; // odd parity
ibm4704_error = IBM4704_ERR_NONE;
idle();
_delay_us(5); // wait for line settles
/* start bit */
WAIT(clock_lo, 100, 0x11); // wait for keyboard to send
WAIT(data_hi, 100, 0x12); // can be delayed that long
WAIT(clock_hi, 100, 0x13); // first rising edge which can take longer
/* data */
for (uint8_t i = 0; i < 8; i++) {
WAIT(clock_hi, 100, 0x20+i);
//_delay_us(5);
if (data_in()) {
parity = !parity;
data |= (1<<i);
}
WAIT(clock_lo, 150, 0x28+i);
}
/* parity */
WAIT(clock_hi, 100, 0x17);
if (data_in() != parity) {
ibm4704_error = IBM4704_ERR_PARITY;
goto ERROR;
}
WAIT(clock_lo, 150, 0x18);
/* stop bit */
WAIT(clock_hi, 100, 0x19);
WAIT(data_lo, 1, 0x19);
inhibit();
_delay_us(200); // wait to recover clock to hi
return data;
ERROR:
if (ibm4704_error > 0x12) {
xprintf("x%02X ", ibm4704_error);
}
inhibit();
_delay_us(200); // wait to recover clock to hi
return -1;
}
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