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