1 /*************************************************************************
2 * Title: I2C master library using hardware TWI interface
3 * Author: Peter Fleury <pfleury@gmx.ch> http://jump.to/fleury
4 * File: $Id: twimaster.c,v 1.3 2005/07/02 11:14:21 Peter Exp $
5 * Software: AVR-GCC 3.4.3 / avr-libc 1.2.3
6 * Target: any AVR device with hardware TWI
7 * Usage: API compatible with I2C Software Library i2cmaster.h
8 **************************************************************************/
10 #include <compat/twi.h>
12 #include <i2cmaster.h>
15 /* define CPU frequency in Mhz here if not defined in Makefile */
17 #define F_CPU 16000000UL
21 #define SCL_CLOCK 400000L
24 /*************************************************************************
25 Initialization of the I2C bus interface. Need to be called only once
26 *************************************************************************/
29 /* initialize TWI clock
30 * minimal values in Bit Rate Register (TWBR) and minimal Prescaler
31 * bits in the TWI Status Register should give us maximal possible
32 * I2C bus speed - about 444 kHz
34 * for more details, see 20.5.2 in ATmega16/32 secification
37 TWSR = 0; /* no prescaler */
38 TWBR = 10; /* must be >= 10 for stable operation */
43 /*************************************************************************
44 Issues a start condition and sends address and transfer direction.
45 return 0 = device accessible, 1= failed to access device
46 *************************************************************************/
47 unsigned char i2c_start(unsigned char address)
51 // send START condition
52 TWCR = (1<<TWINT) | (1<<TWSTA) | (1<<TWEN);
54 // wait until transmission completed
55 while(!(TWCR & (1<<TWINT)));
57 // check value of TWI Status Register. Mask prescaler bits.
58 twst = TW_STATUS & 0xF8;
59 if ( (twst != TW_START) && (twst != TW_REP_START)) return 1;
61 // send device address
63 TWCR = (1<<TWINT) | (1<<TWEN);
65 // wail until transmission completed and ACK/NACK has been received
66 while(!(TWCR & (1<<TWINT)));
68 // check value of TWI Status Register. Mask prescaler bits.
69 twst = TW_STATUS & 0xF8;
70 if ( (twst != TW_MT_SLA_ACK) && (twst != TW_MR_SLA_ACK) ) return 1;
77 /*************************************************************************
78 Issues a start condition and sends address and transfer direction.
79 If device is busy, use ack polling to wait until device is ready
81 Input: address and transfer direction of I2C device
82 *************************************************************************/
83 void i2c_start_wait(unsigned char address)
90 // send START condition
91 TWCR = (1<<TWINT) | (1<<TWSTA) | (1<<TWEN);
93 // wait until transmission completed
94 while(!(TWCR & (1<<TWINT)));
96 // check value of TWI Status Register. Mask prescaler bits.
97 twst = TW_STATUS & 0xF8;
98 if ( (twst != TW_START) && (twst != TW_REP_START)) continue;
100 // send device address
102 TWCR = (1<<TWINT) | (1<<TWEN);
104 // wail until transmission completed
105 while(!(TWCR & (1<<TWINT)));
107 // check value of TWI Status Register. Mask prescaler bits.
108 twst = TW_STATUS & 0xF8;
109 if ( (twst == TW_MT_SLA_NACK )||(twst ==TW_MR_DATA_NACK) )
111 /* device busy, send stop condition to terminate write operation */
112 TWCR = (1<<TWINT) | (1<<TWEN) | (1<<TWSTO);
114 // wait until stop condition is executed and bus released
115 while(TWCR & (1<<TWSTO));
119 //if( twst != TW_MT_SLA_ACK) return 1;
123 }/* i2c_start_wait */
126 /*************************************************************************
127 Issues a repeated start condition and sends address and transfer direction
129 Input: address and transfer direction of I2C device
131 Return: 0 device accessible
132 1 failed to access device
133 *************************************************************************/
134 unsigned char i2c_rep_start(unsigned char address)
136 return i2c_start( address );
141 /*************************************************************************
142 Terminates the data transfer and releases the I2C bus
143 *************************************************************************/
146 /* send stop condition */
147 TWCR = (1<<TWINT) | (1<<TWEN) | (1<<TWSTO);
149 // wait until stop condition is executed and bus released
150 while(TWCR & (1<<TWSTO));
155 /*************************************************************************
156 Send one byte to I2C device
158 Input: byte to be transfered
159 Return: 0 write successful
161 *************************************************************************/
162 unsigned char i2c_write( unsigned char data )
166 // send data to the previously addressed device
168 TWCR = (1<<TWINT) | (1<<TWEN);
170 // wait until transmission completed
171 while(!(TWCR & (1<<TWINT)));
173 // check value of TWI Status Register. Mask prescaler bits
174 twst = TW_STATUS & 0xF8;
175 if( twst != TW_MT_DATA_ACK) return 1;
181 /*************************************************************************
182 Read one byte from the I2C device, request more data from device
184 Return: byte read from I2C device
185 *************************************************************************/
186 unsigned char i2c_readAck(void)
188 TWCR = (1<<TWINT) | (1<<TWEN) | (1<<TWEA);
189 while(!(TWCR & (1<<TWINT)));
196 /*************************************************************************
197 Read one byte from the I2C device, read is followed by a stop condition
199 Return: byte read from I2C device
200 *************************************************************************/
201 unsigned char i2c_readNak(void)
203 TWCR = (1<<TWINT) | (1<<TWEN);
204 while(!(TWCR & (1<<TWINT)));