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Diffstat (limited to 'keyboard/ergodox_ez/twimaster.c')
| -rw-r--r-- | keyboard/ergodox_ez/twimaster.c | 208 |
1 files changed, 208 insertions, 0 deletions
diff --git a/keyboard/ergodox_ez/twimaster.c b/keyboard/ergodox_ez/twimaster.c new file mode 100644 index 0000000000..f91c08e6e4 --- /dev/null +++ b/keyboard/ergodox_ez/twimaster.c @@ -0,0 +1,208 @@ +/************************************************************************* +* Title: I2C master library using hardware TWI interface +* Author: Peter Fleury <pfleury@gmx.ch> http://jump.to/fleury +* File: $Id: twimaster.c,v 1.3 2005/07/02 11:14:21 Peter Exp $ +* Software: AVR-GCC 3.4.3 / avr-libc 1.2.3 +* Target: any AVR device with hardware TWI +* Usage: API compatible with I2C Software Library i2cmaster.h +**************************************************************************/ +#include <inttypes.h> +#include <compat/twi.h> + +#include <i2cmaster.h> + + +/* define CPU frequency in Mhz here if not defined in Makefile */ +#ifndef F_CPU +#define F_CPU 16000000UL +#endif + +/* I2C clock in Hz */ +#define SCL_CLOCK 400000L + + +/************************************************************************* + Initialization of the I2C bus interface. Need to be called only once +*************************************************************************/ +void i2c_init(void) +{ + /* initialize TWI clock + * minimal values in Bit Rate Register (TWBR) and minimal Prescaler + * bits in the TWI Status Register should give us maximal possible + * I2C bus speed - about 444 kHz + * + * for more details, see 20.5.2 in ATmega16/32 secification + */ + + TWSR = 0; /* no prescaler */ + TWBR = 10; /* must be >= 10 for stable operation */ + +}/* i2c_init */ + + +/************************************************************************* + Issues a start condition and sends address and transfer direction. + return 0 = device accessible, 1= failed to access device +*************************************************************************/ +unsigned char i2c_start(unsigned char address) +{ + uint8_t twst; + + // send START condition + TWCR = (1<<TWINT) | (1<<TWSTA) | (1<<TWEN); + + // wait until transmission completed + while(!(TWCR & (1<<TWINT))); + + // check value of TWI Status Register. Mask prescaler bits. + twst = TW_STATUS & 0xF8; + if ( (twst != TW_START) && (twst != TW_REP_START)) return 1; + + // send device address + TWDR = address; + TWCR = (1<<TWINT) | (1<<TWEN); + + // wail until transmission completed and ACK/NACK has been received + while(!(TWCR & (1<<TWINT))); + + // check value of TWI Status Register. Mask prescaler bits. + twst = TW_STATUS & 0xF8; + if ( (twst != TW_MT_SLA_ACK) && (twst != TW_MR_SLA_ACK) ) return 1; + + return 0; + +}/* i2c_start */ + + +/************************************************************************* + Issues a start condition and sends address and transfer direction. + If device is busy, use ack polling to wait until device is ready + + Input: address and transfer direction of I2C device +*************************************************************************/ +void i2c_start_wait(unsigned char address) +{ + uint8_t twst; + + + while ( 1 ) + { + // send START condition + TWCR = (1<<TWINT) | (1<<TWSTA) | (1<<TWEN); + + // wait until transmission completed + while(!(TWCR & (1<<TWINT))); + + // check value of TWI Status Register. Mask prescaler bits. + twst = TW_STATUS & 0xF8; + if ( (twst != TW_START) && (twst != TW_REP_START)) continue; + + // send device address + TWDR = address; + TWCR = (1<<TWINT) | (1<<TWEN); + + // wail until transmission completed + while(!(TWCR & (1<<TWINT))); + + // check value of TWI Status Register. Mask prescaler bits. + twst = TW_STATUS & 0xF8; + if ( (twst == TW_MT_SLA_NACK )||(twst ==TW_MR_DATA_NACK) ) + { + /* device busy, send stop condition to terminate write operation */ + TWCR = (1<<TWINT) | (1<<TWEN) | (1<<TWSTO); + + // wait until stop condition is executed and bus released + while(TWCR & (1<<TWSTO)); + + continue; + } + //if( twst != TW_MT_SLA_ACK) return 1; + break; + } + +}/* i2c_start_wait */ + + +/************************************************************************* + Issues a repeated start condition and sends address and transfer direction + + Input: address and transfer direction of I2C device + + Return: 0 device accessible + 1 failed to access device +*************************************************************************/ +unsigned char i2c_rep_start(unsigned char address) +{ + return i2c_start( address ); + +}/* i2c_rep_start */ + + +/************************************************************************* + Terminates the data transfer and releases the I2C bus +*************************************************************************/ +void i2c_stop(void) +{ + /* send stop condition */ + TWCR = (1<<TWINT) | (1<<TWEN) | (1<<TWSTO); + + // wait until stop condition is executed and bus released + while(TWCR & (1<<TWSTO)); + +}/* i2c_stop */ + + +/************************************************************************* + Send one byte to I2C device + + Input: byte to be transfered + Return: 0 write successful + 1 write failed +*************************************************************************/ +unsigned char i2c_write( unsigned char data ) +{ + uint8_t twst; + + // send data to the previously addressed device + TWDR = data; + TWCR = (1<<TWINT) | (1<<TWEN); + + // wait until transmission completed + while(!(TWCR & (1<<TWINT))); + + // check value of TWI Status Register. Mask prescaler bits + twst = TW_STATUS & 0xF8; + if( twst != TW_MT_DATA_ACK) return 1; + return 0; + +}/* i2c_write */ + + +/************************************************************************* + Read one byte from the I2C device, request more data from device + + Return: byte read from I2C device +*************************************************************************/ +unsigned char i2c_readAck(void) +{ + TWCR = (1<<TWINT) | (1<<TWEN) | (1<<TWEA); + while(!(TWCR & (1<<TWINT))); + + return TWDR; + +}/* i2c_readAck */ + + +/************************************************************************* + Read one byte from the I2C device, read is followed by a stop condition + + Return: byte read from I2C device +*************************************************************************/ +unsigned char i2c_readNak(void) +{ + TWCR = (1<<TWINT) | (1<<TWEN); + while(!(TWCR & (1<<TWINT))); + + return TWDR; + +}/* i2c_readNak */ |