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, uint8_t TimeoutMS)
  11 {
  12         for (;;)
  13         {
  14                 bool     BusCaptured = false;
  15                 uint16_t TimeoutRemaining;
  16
  17                 TWCR = ((1 << TWINT) | (1 << TWSTA) | (1 << TWEN));
  18
  19                 TimeoutRemaining = (TimeoutMS * 100);
  20                 while (TimeoutRemaining-- && !(BusCaptured))
  21                 {
  22                         if (TWCR & (1 << TWINT))
  23                         {
  24                                 switch (TWSR & TW_STATUS_MASK)
  25                                 {
  26                                         case TW_START:
  27                                         case TW_REP_START:
  28                                                 BusCaptured = true;
  29                                                 break;
  30                                         case TW_MT_ARB_LOST:
  31                                                 TWCR = ((1 << TWINT) | (1 << TWSTA) | (1 << TWEN));
  32                                                 continue;
  33                                         default:
  34                                                 TWCR = (1 << TWEN);
  35                                                 return false;
  36                                 }
  37                         }
  38
  39                         _delay_us(10);
  40                 }
  41
  42                 if (!(BusCaptured))
  43                 {
  44                         TWCR = (1 << TWEN);
  45                         return false;
  46                 }
  47
  48                 TWDR = SlaveAddress;
  49                 TWCR = ((1 << TWINT) | (1 << TWEN));
  50
  51                 TimeoutRemaining = (TimeoutMS * 100);
  52                 while (TimeoutRemaining--)
  53                 {
  54                         if (TWCR & (1 << TWINT))
  55                           break;
  56
  57                         _delay_us(10);
  58                 }
  59
  60                 if (!(TimeoutRemaining))
  61                   return false;
  62
  63                 switch (TWSR & TW_STATUS_MASK)
  64                 {
  65                         case TW_MT_SLA_ACK:
  66                         case TW_MR_SLA_ACK:
  67                                 return true;
  68                         default:
  69                                 TWCR = ((1 << TWINT) | (1 << TWSTO) | (1 << TWEN));
  70                                 return false;
  71                 }
  72         }
  73 }