You can not select more than 25 topics
Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
202 lines
5.8 KiB
202 lines
5.8 KiB
/*************************************************************************
|
|
* Title: I2C master library using hardware TWI interface
|
|
* Author: Peter Fleury <pfleury@gmx.ch> http://jump.to/fleury
|
|
* File: $Id: twimaster.c,v 1.4 2015/01/17 12:16:05 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 <avr/io.h>
|
|
|
|
#include "i2cMaster.h"
|
|
|
|
/* define CPU frequency in hz here if not defined in Makefile */
|
|
#ifndef F_CPU
|
|
#define F_CPU 16000000UL
|
|
#endif
|
|
|
|
/* I2C clock in Hz */
|
|
#define SCL_CLOCK 100000L
|
|
|
|
/*************************************************************************
|
|
Initialization of the I2C bus interface. Need to be called only once
|
|
*************************************************************************/
|
|
void initI2C(void)
|
|
{
|
|
/* initialize TWI clock: 100 kHz clock, TWPS = 0 => prescaler = 1 */
|
|
TWI_BUS_PORT |= 1<<SCL|1<<SDA;
|
|
TWI_BUS_DDR &=~(1<<SCL|1<<SDA);
|
|
TWSR = 0; /* no prescaler */
|
|
TWBR = ((F_CPU/SCL_CLOCK)-16)/2; /* must be > 10 for stable operation */
|
|
}
|
|
|
|
/*************************************************************************
|
|
Issues a start condition and sends address and transfer direction.
|
|
return 0 = device accessible, 1= start condition didn't transmit,
|
|
2= master as transmitter/receiver didn't receive an ACK
|
|
*************************************************************************/
|
|
uint8_t i2cStart(uint8_t 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; // (repeated) start condition NOT transmitted
|
|
|
|
// 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 2; // master as transmitter/receiver didn't receive ACK
|
|
|
|
return 0;
|
|
}
|
|
|
|
|
|
/*************************************************************************
|
|
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 i2cStartWait(uint8_t 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;
|
|
}
|
|
|
|
break;
|
|
}
|
|
}
|
|
|
|
/*************************************************************************
|
|
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
|
|
*************************************************************************/
|
|
uint8_t i2cRepeatStart(uint8_t address)
|
|
{
|
|
return i2cStart(address);
|
|
}
|
|
|
|
/*************************************************************************
|
|
Terminates the data transfer and releases the I2C bus
|
|
*************************************************************************/
|
|
void i2cStop(void)
|
|
{
|
|
/* send stop condition */
|
|
TWCR = (1 << TWINT | 1 << TWEN | 1 << TWSTO);
|
|
|
|
// wait until stop condition is executed and bus released
|
|
while(TWCR & (1 << TWSTO))
|
|
;
|
|
}
|
|
|
|
/*************************************************************************
|
|
Send one byte to I2C device
|
|
|
|
Input: byte to be transfered
|
|
Return: 0 write successful
|
|
1 write failed
|
|
*************************************************************************/
|
|
uint8_t i2cWrite(uint8_t 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;
|
|
}
|
|
|
|
/*************************************************************************
|
|
Read one byte from the I2C device, request more data from device
|
|
|
|
Return: byte read from I2C device
|
|
*************************************************************************/
|
|
uint8_t i2cReadAck(void)
|
|
{
|
|
TWCR = (1 << TWINT | 1 << TWEN | 1 << TWEA);
|
|
while(!(TWCR & (1 << TWINT)))
|
|
;
|
|
|
|
return TWDR;
|
|
}
|
|
|
|
/*************************************************************************
|
|
Read one byte from the I2C device, read is followed by a stop condition
|
|
|
|
Return: byte read from I2C device
|
|
*************************************************************************/
|
|
uint8_t i2cReadNak(void)
|
|
{
|
|
TWCR = (1 << TWINT | 1 << TWEN);
|
|
while(!(TWCR & (1 << TWINT)))
|
|
;
|
|
|
|
return TWDR;
|
|
}
|