LUFA/Drivers/Peripheral/TWI.c

   1 /*
   2      Copyright (C) Dean Camera, 2010.
   3
   4   dean [at] fourwalledcubicle [dot] com
   5       www.fourwalledcubicle.com
   6 */
   7
   8 #include "TWI.h"
   9
  10 bool TWI_StartTransmission(uint8_t SlaveAddress)
  11 {
  12         for (;;)
  13         {
  14                 uint8_t IterationsRemaining = 50;
  15                 bool    BusCaptured = false;
  16
  17                 while (IterationsRemaining-- && !BusCaptured)
  18                 {
  19                         TWCR = ((1 << TWINT) | (1 << TWSTA) | (1 << TWEN));
  20                         while (!(TWCR & (1 << TWINT)));
  21
  22                         switch (TWSR & TW_STATUS_MASK)
  23                         {
  24                                 case TW_START:
  25                                 case TW_REP_START:
  26                                         BusCaptured = true;
  27                                         break;
  28                                 case TW_MT_ARB_LOST:
  29                                         continue;
  30                                 default:
  31                                         return false;
  32                         }
  33                 }
  34
  35                 if (!(BusCaptured))
  36                   return false;
  37
  38                 TWDR = SlaveAddress;
  39                 TWCR = ((1 << TWINT) | (1 << TWEN));
  40                 while (!(TWCR & (1 << TWINT)));
  41
  42                 GPIOR0 = (TWSR & TW_STATUS_MASK);
  43
  44                 switch (TWSR & TW_STATUS_MASK)
  45                 {
  46                         case TW_MT_SLA_ACK:
  47                         case TW_MR_SLA_ACK:
  48                                 return true;
  49                         default:
  50                                 TWI_StopTransmission();
  51                                 break;
  52                 }
  53         }
  54 }