keyboard/ergodox/twimaster.c

   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 **************************************************************************/
   9 #include <inttypes.h>
  10 #include <compat/twi.h>
  11
  12 #include <i2cmaster.h>
  13
  14
  15 /* define CPU frequency in Mhz here if not defined in Makefile */
  16 #ifndef F_CPU
  17 #define F_CPU 16000000UL
  18 #endif
  19
  20 /* I2C clock in Hz */
  21 #define SCL_CLOCK  400000L
  22
  23
  24 /*************************************************************************
  25  Initialization of the I2C bus interface. Need to be called only once
  26 *************************************************************************/
  27 void i2c_init(void)
  28 {
  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
  33    *
  34    * for more details, see 20.5.2 in ATmega16/32 secification
  35    */
  36
  37   TWSR = 0;     /* no prescaler */
  38   TWBR = 10;    /* must be >= 10 for stable operation */
  39
  40 }/* i2c_init */
  41
  42
  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)
  48 {
  49     uint8_t   twst;
  50
  51         // send START condition
  52         TWCR = (1<<TWINT) | (1<<TWSTA) | (1<<TWEN);
  53
  54         // wait until transmission completed
  55         while(!(TWCR & (1<<TWINT)));
  56
  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;
  60
  61         // send device address
  62         TWDR = address;
  63         TWCR = (1<<TWINT) | (1<<TWEN);
  64
  65         // wail until transmission completed and ACK/NACK has been received
  66         while(!(TWCR & (1<<TWINT)));
  67
  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;
  71
  72         return 0;
  73
  74 }/* i2c_start */
  75
  76
  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
  80
  81  Input:   address and transfer direction of I2C device
  82 *************************************************************************/
  83 void i2c_start_wait(unsigned char address)
  84 {
  85     uint8_t   twst;
  86
  87
  88     while ( 1 )
  89     {
  90             // send START condition
  91             TWCR = (1<<TWINT) | (1<<TWSTA) | (1<<TWEN);
  92
  93         // wait until transmission completed
  94         while(!(TWCR & (1<<TWINT)));
  95
  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;
  99
 100         // send device address
 101         TWDR = address;
 102         TWCR = (1<<TWINT) | (1<<TWEN);
 103
 104         // wail until transmission completed
 105         while(!(TWCR & (1<<TWINT)));
 106
 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) )
 110         {
 111             /* device busy, send stop condition to terminate write operation */
 112                 TWCR = (1<<TWINT) | (1<<TWEN) | (1<<TWSTO);
 113
 114                 // wait until stop condition is executed and bus released
 115                 while(TWCR & (1<<TWSTO));
 116
 117             continue;
 118         }
 119         //if( twst != TW_MT_SLA_ACK) return 1;
 120         break;
 121      }
 122
 123 }/* i2c_start_wait */
 124
 125
 126 /*************************************************************************
 127  Issues a repeated start condition and sends address and transfer direction
 128
 129  Input:   address and transfer direction of I2C device
 130
 131  Return:  0 device accessible
 132           1 failed to access device
 133 *************************************************************************/
 134 unsigned char i2c_rep_start(unsigned char address)
 135 {
 136     return i2c_start( address );
 137
 138 }/* i2c_rep_start */
 139
 140
 141 /*************************************************************************
 142  Terminates the data transfer and releases the I2C bus
 143 *************************************************************************/
 144 void i2c_stop(void)
 145 {
 146     /* send stop condition */
 147         TWCR = (1<<TWINT) | (1<<TWEN) | (1<<TWSTO);
 148
 149         // wait until stop condition is executed and bus released
 150         while(TWCR & (1<<TWSTO));
 151
 152 }/* i2c_stop */
 153
 154
 155 /*************************************************************************
 156   Send one byte to I2C device
 157
 158   Input:    byte to be transfered
 159   Return:   0 write successful
 160             1 write failed
 161 *************************************************************************/
 162 unsigned char i2c_write( unsigned char data )
 163 {
 164     uint8_t   twst;
 165
 166         // send data to the previously addressed device
 167         TWDR = data;
 168         TWCR = (1<<TWINT) | (1<<TWEN);
 169
 170         // wait until transmission completed
 171         while(!(TWCR & (1<<TWINT)));
 172
 173         // check value of TWI Status Register. Mask prescaler bits
 174         twst = TW_STATUS & 0xF8;
 175         if( twst != TW_MT_DATA_ACK) return 1;
 176         return 0;
 177
 178 }/* i2c_write */
 179
 180
 181 /*************************************************************************
 182  Read one byte from the I2C device, request more data from device
 183
 184  Return:  byte read from I2C device
 185 *************************************************************************/
 186 unsigned char i2c_readAck(void)
 187 {
 188         TWCR = (1<<TWINT) | (1<<TWEN) | (1<<TWEA);
 189         while(!(TWCR & (1<<TWINT)));
 190
 191     return TWDR;
 192
 193 }/* i2c_readAck */
 194
 195
 196 /*************************************************************************
 197  Read one byte from the I2C device, read is followed by a stop condition
 198
 199  Return:  byte read from I2C device
 200 *************************************************************************/
 201 unsigned char i2c_readNak(void)
 202 {
 203         TWCR = (1<<TWINT) | (1<<TWEN);
 204         while(!(TWCR & (1<<TWINT)));
 205
 206     return TWDR;
 207
 208 }/* i2c_readNak */