mirror of
https://github.com/openstenoproject/qmk
synced 2024-11-14 12:34:39 +00:00
208 lines
6 KiB
C
208 lines
6 KiB
C
/*************************************************************************
|
|
* 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 */
|