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| Rev | Author | Line No. | Line |
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| 2194 | - | 1 | /************************************************************************* |
| 2 | * Title: I2C master library using hardware TWI interface |
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| 3 | * Author: Peter Fleury <pfleury@gmx.ch> http://jump.to/fleury |
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| 4 | * File: $Id: twimaster.c,v 1.3 2005/07/02 11:14:21 Peter Exp $ |
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| 5 | * Software: AVR-GCC 3.4.3 / avr-libc 1.2.3 |
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| 6 | * Target: any AVR device with hardware TWI |
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| 7 | * Usage: API compatible with I2C Software Library i2cmaster.h |
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| 8 | **************************************************************************/ |
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| 9 | #include <inttypes.h> |
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| 10 | #include <compat/twi.h> |
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| 11 | |||
| 12 | #include <i2cmaster.h> |
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| 13 | |||
| 14 | |||
| 15 | /* define CPU frequency in Mhz here if not defined in Makefile */ |
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| 16 | #ifndef F_CPU |
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| 17 | #define F_CPU 16000000UL |
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| 18 | #endif |
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| 19 | |||
| 20 | /* I2C clock in Hz */ |
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| 21 | #define SCL_CLOCK 400000L |
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| 22 | |||
| 23 | |||
| 24 | /************************************************************************* |
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| 25 | Initialization of the I2C bus interface. Need to be called only once |
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| 26 | *************************************************************************/ |
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| 27 | void i2c_init(void) |
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| 28 | { |
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| 29 | /* initialize TWI clock: 100 kHz clock, TWPS = 0 => prescaler = 1 */ |
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| 30 | |||
| 31 | TWSR = 0; /* no prescaler */ |
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| 32 | TWBR = ((F_CPU/SCL_CLOCK)-16)/2; /* must be > 10 for stable operation */ |
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| 33 | |||
| 34 | }/* i2c_init */ |
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| 35 | |||
| 36 | |||
| 37 | /************************************************************************* |
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| 38 | Issues a start condition and sends address and transfer direction. |
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| 39 | return 0 = device accessible, 1= failed to access device |
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| 40 | *************************************************************************/ |
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| 41 | unsigned char i2c_start(unsigned char address) |
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| 42 | { |
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| 43 | uint8_t twst; |
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| 44 | |||
| 45 | // send START condition |
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| 46 | TWCR = (1<<TWINT) | (1<<TWSTA) | (1<<TWEN); |
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| 47 | |||
| 48 | // wait until transmission completed |
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| 49 | while(!(TWCR & (1<<TWINT))); |
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| 50 | |||
| 51 | // check value of TWI Status Register. Mask prescaler bits. |
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| 52 | twst = TW_STATUS & 0xF8; |
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| 53 | if ( (twst != TW_START) && (twst != TW_REP_START)) return 1; |
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| 54 | |||
| 55 | // send device address |
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| 56 | TWDR = address; |
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| 57 | TWCR = (1<<TWINT) | (1<<TWEN); |
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| 58 | |||
| 59 | // wail until transmission completed and ACK/NACK has been received |
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| 60 | while(!(TWCR & (1<<TWINT))); |
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| 61 | |||
| 62 | // check value of TWI Status Register. Mask prescaler bits. |
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| 63 | twst = TW_STATUS & 0xF8; |
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| 64 | if ( (twst != TW_MT_SLA_ACK) && (twst != TW_MR_SLA_ACK) ) return 1; |
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| 65 | |||
| 66 | return 0; |
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| 67 | |||
| 68 | }/* i2c_start */ |
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| 69 | |||
| 70 | |||
| 71 | /************************************************************************* |
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| 72 | Issues a start condition and sends address and transfer direction. |
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| 73 | If device is busy, use ack polling to wait until device is ready |
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| 74 | |||
| 75 | Input: address and transfer direction of I2C device |
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| 76 | *************************************************************************/ |
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| 77 | void i2c_start_wait(unsigned char address) |
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| 78 | { |
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| 79 | uint8_t twst; |
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| 80 | |||
| 81 | |||
| 82 | while ( 1 ) |
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| 83 | { |
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| 84 | // send START condition |
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| 85 | TWCR = (1<<TWINT) | (1<<TWSTA) | (1<<TWEN); |
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| 86 | |||
| 87 | // wait until transmission completed |
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| 88 | while(!(TWCR & (1<<TWINT))); |
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| 89 | |||
| 90 | // check value of TWI Status Register. Mask prescaler bits. |
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| 91 | twst = TW_STATUS & 0xF8; |
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| 92 | if ( (twst != TW_START) && (twst != TW_REP_START)) continue; |
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| 93 | |||
| 94 | // send device address |
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| 95 | TWDR = address; |
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| 96 | TWCR = (1<<TWINT) | (1<<TWEN); |
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| 97 | |||
| 98 | // wail until transmission completed |
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| 99 | while(!(TWCR & (1<<TWINT))); |
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| 100 | |||
| 101 | // check value of TWI Status Register. Mask prescaler bits. |
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| 102 | twst = TW_STATUS & 0xF8; |
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| 103 | if ( (twst == TW_MT_SLA_NACK )||(twst ==TW_MR_DATA_NACK) ) |
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| 104 | { |
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| 105 | /* device busy, send stop condition to terminate write operation */ |
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| 106 | TWCR = (1<<TWINT) | (1<<TWEN) | (1<<TWSTO); |
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| 107 | |||
| 108 | // wait until stop condition is executed and bus released |
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| 109 | while(TWCR & (1<<TWSTO)); |
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| 110 | |||
| 111 | continue; |
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| 112 | } |
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| 113 | //if( twst != TW_MT_SLA_ACK) return 1; |
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| 114 | break; |
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| 115 | } |
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| 116 | |||
| 117 | }/* i2c_start_wait */ |
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| 118 | |||
| 119 | |||
| 120 | /************************************************************************* |
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| 121 | Issues a repeated start condition and sends address and transfer direction |
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| 122 | |||
| 123 | Input: address and transfer direction of I2C device |
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| 124 | |||
| 125 | Return: 0 device accessible |
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| 126 | 1 failed to access device |
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| 127 | *************************************************************************/ |
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| 128 | unsigned char i2c_rep_start(unsigned char address) |
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| 129 | { |
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| 130 | return i2c_start( address ); |
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| 131 | |||
| 132 | }/* i2c_rep_start */ |
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| 133 | |||
| 134 | |||
| 135 | /************************************************************************* |
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| 136 | Terminates the data transfer and releases the I2C bus |
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| 137 | *************************************************************************/ |
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| 138 | void i2c_stop(void) |
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| 139 | { |
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| 140 | /* send stop condition */ |
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| 141 | TWCR = (1<<TWINT) | (1<<TWEN) | (1<<TWSTO); |
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| 142 | |||
| 143 | // wait until stop condition is executed and bus released |
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| 144 | while(TWCR & (1<<TWSTO)); |
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| 145 | |||
| 146 | }/* i2c_stop */ |
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| 147 | |||
| 148 | |||
| 149 | /************************************************************************* |
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| 150 | Send one byte to I2C device |
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| 151 | |||
| 152 | Input: byte to be transfered |
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| 153 | Return: 0 write successful |
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| 154 | 1 write failed |
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| 155 | *************************************************************************/ |
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| 156 | unsigned char i2c_write( unsigned char data ) |
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| 157 | { |
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| 158 | uint8_t twst; |
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| 159 | |||
| 160 | // send data to the previously addressed device |
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| 161 | TWDR = data; |
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| 162 | TWCR = (1<<TWINT) | (1<<TWEN); |
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| 163 | |||
| 164 | // wait until transmission completed |
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| 165 | while(!(TWCR & (1<<TWINT))); |
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| 166 | |||
| 167 | // check value of TWI Status Register. Mask prescaler bits |
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| 168 | twst = TW_STATUS & 0xF8; |
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| 169 | if( twst != TW_MT_DATA_ACK) return 1; |
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| 170 | return 0; |
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| 171 | |||
| 172 | }/* i2c_write */ |
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| 173 | |||
| 174 | |||
| 175 | /************************************************************************* |
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| 176 | Read one byte from the I2C device, request more data from device |
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| 177 | |||
| 178 | Return: byte read from I2C device |
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| 179 | *************************************************************************/ |
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| 180 | unsigned char i2c_readAck(void) |
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| 181 | { |
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| 182 | TWCR = (1<<TWINT) | (1<<TWEN) | (1<<TWEA); |
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| 183 | while(!(TWCR & (1<<TWINT))); |
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| 184 | |||
| 185 | return TWDR; |
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| 186 | |||
| 187 | }/* i2c_readAck */ |
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| 188 | |||
| 189 | |||
| 190 | /************************************************************************* |
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| 191 | Read one byte from the I2C device, read is followed by a stop condition |
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| 192 | |||
| 193 | Return: byte read from I2C device |
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| 194 | *************************************************************************/ |
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| 195 | unsigned char i2c_readNak(void) |
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| 196 | { |
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| 197 | TWCR = (1<<TWINT) | (1<<TWEN); |
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| 198 | while(!(TWCR & (1<<TWINT))); |
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| 199 | |||
| 200 | return TWDR; |
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| 201 | |||
| 202 | }/* i2c_readNak */ |