LUFA/Drivers/Peripheral/TWI.c

   1 /*
   2      Copyright (C) Dean Camera, 2010.
   3
   4   dean [at] fourwalledcubicle [dot] com
   5            www.lufa-lib.org
   6 */
   7
   8 #include "TWI.h"
   9
  10 bool TWI_StartTransmission(const uint8_t SlaveAddress,
  11                            const uint8_t TimeoutMS)
  12 {
  13         for (;;)
  14         {
  15                 bool     BusCaptured = false;
  16                 uint16_t TimeoutRemaining;
  17
  18                 TWCR = ((1 << TWINT) | (1 << TWSTA) | (1 << TWEN));
  19
  20                 TimeoutRemaining = (TimeoutMS * 100);
  21                 while (TimeoutRemaining-- && !(BusCaptured))
  22                 {
  23                         if (TWCR & (1 << TWINT))
  24                         {
  25                                 switch (TWSR & TW_STATUS_MASK)
  26                                 {
  27                                         case TW_START:
  28                                         case TW_REP_START:
  29                                                 BusCaptured = true;
  30                                                 break;
  31                                         case TW_MT_ARB_LOST:
  32                                                 TWCR = ((1 << TWINT) | (1 << TWSTA) | (1 << TWEN));
  33                                                 continue;
  34                                         default:
  35                                                 TWCR = (1 << TWEN);
  36                                                 return false;
  37                                 }
  38                         }
  39
  40                         _delay_us(10);
  41                 }
  42
  43                 if (!(BusCaptured))
  44                 {
  45                         TWCR = (1 << TWEN);
  46                         return false;
  47                 }
  48
  49                 TWDR = SlaveAddress;
  50                 TWCR = ((1 << TWINT) | (1 << TWEN));
  51
  52                 TimeoutRemaining = (TimeoutMS * 100);
  53                 while (TimeoutRemaining--)
  54                 {
  55                         if (TWCR & (1 << TWINT))
  56                           break;
  57
  58                         _delay_us(10);
  59                 }
  60
  61                 if (!(TimeoutRemaining))
  62                   return false;
  63
  64                 switch (TWSR & TW_STATUS_MASK)
  65                 {
  66                         case TW_MT_SLA_ACK:
  67                         case TW_MR_SLA_ACK:
  68                                 return true;
  69                         default:
  70                                 TWCR = ((1 << TWINT) | (1 << TWSTO) | (1 << TWEN));
  71                                 return false;
  72                 }
  73         }
  74 }
  75