drivers/avr/TWIlib.c

   1 /*
   2  * TWIlib.c
   3  *
   4  *  Created: 6/01/2014 10:41:33 PM
   5  *  Author: Chris Herring
   6  *  http://www.chrisherring.net/all/tutorial-interrupt-driven-twi-interface-for-avr-part1/
   7  */
   8
   9 #include <avr/io.h>
  10 #include <avr/interrupt.h>
  11 #include "TWIlib.h"
  12 #include "util/delay.h"
  13
  14 void TWIInit()
  15 {
  16         TWIInfo.mode = Ready;
  17         TWIInfo.errorCode = 0xFF;
  18         TWIInfo.repStart = 0;
  19         // Set pre-scalers (no pre-scaling)
  20         TWSR = 0;
  21         // Set bit rate
  22         TWBR = ((F_CPU / TWI_FREQ) - 16) / 2;
  23         // Enable TWI and interrupt
  24         TWCR = (1 << TWIE) | (1 << TWEN);
  25 }
  26
  27 uint8_t isTWIReady()
  28 {
  29         if ( (TWIInfo.mode == Ready) | (TWIInfo.mode == RepeatedStartSent) )
  30         {
  31                 return 1;
  32         }
  33         else
  34         {
  35                 return 0;
  36         }
  37 }
  38
  39 uint8_t TWITransmitData(void *const TXdata, uint8_t dataLen, uint8_t repStart)
  40 {
  41         if (dataLen <= TXMAXBUFLEN)
  42         {
  43                 // Wait until ready
  44                 while (!isTWIReady()) {_delay_us(1);}
  45                 // Set repeated start mode
  46                 TWIInfo.repStart = repStart;
  47                 // Copy data into the transmit buffer
  48                 uint8_t *data = (uint8_t *)TXdata;
  49                 for (int i = 0; i < dataLen; i++)
  50                 {
  51                         TWITransmitBuffer[i] = data[i];
  52                 }
  53                 // Copy transmit info to global variables
  54                 TXBuffLen = dataLen;
  55                 TXBuffIndex = 0;
  56
  57                 // If a repeated start has been sent, then devices are already listening for an address
  58                 // and another start does not need to be sent.
  59                 if (TWIInfo.mode == RepeatedStartSent)
  60                 {
  61                         TWIInfo.mode = Initializing;
  62                         TWDR = TWITransmitBuffer[TXBuffIndex++]; // Load data to transmit buffer
  63                         TWISendTransmit(); // Send the data
  64                 }
  65                 else // Otherwise, just send the normal start signal to begin transmission.
  66                 {
  67                         TWIInfo.mode = Initializing;
  68                         TWISendStart();
  69                 }
  70
  71         }
  72         else
  73         {
  74                 return 1; // return an error if data length is longer than buffer
  75         }
  76         return 0;
  77 }
  78
  79 uint8_t TWIReadData(uint8_t TWIaddr, uint8_t bytesToRead, uint8_t repStart)
  80 {
  81         // Check if number of bytes to read can fit in the RXbuffer
  82         if (bytesToRead < RXMAXBUFLEN)
  83         {
  84                 // Reset buffer index and set RXBuffLen to the number of bytes to read
  85                 RXBuffIndex = 0;
  86                 RXBuffLen = bytesToRead;
  87                 // Create the one value array for the address to be transmitted
  88                 uint8_t TXdata[1];
  89                 // Shift the address and AND a 1 into the read write bit (set to write mode)
  90                 TXdata[0] = (TWIaddr << 1) | 0x01;
  91                 // Use the TWITransmitData function to initialize the transfer and address the slave
  92                 TWITransmitData(TXdata, 1, repStart);
  93         }
  94         else
  95         {
  96                 return 0;
  97         }
  98         return 1;
  99 }
 100
 101 ISR (TWI_vect)
 102 {
 103         switch (TWI_STATUS)
 104         {
 105                 // ----\/ ---- MASTER TRANSMITTER OR WRITING ADDRESS ----\/ ----  //
 106                 case TWI_MT_SLAW_ACK: // SLA+W transmitted and ACK received
 107                 // Set mode to Master Transmitter
 108                 TWIInfo.mode = MasterTransmitter;
 109                 case TWI_START_SENT: // Start condition has been transmitted
 110                 case TWI_MT_DATA_ACK: // Data byte has been transmitted, ACK received
 111                         if (TXBuffIndex < TXBuffLen) // If there is more data to send
 112                         {
 113                                 TWDR = TWITransmitBuffer[TXBuffIndex++]; // Load data to transmit buffer
 114                                 TWIInfo.errorCode = TWI_NO_RELEVANT_INFO;
 115                                 TWISendTransmit(); // Send the data
 116                         }
 117                         // This transmission is complete however do not release bus yet
 118                         else if (TWIInfo.repStart)
 119                         {
 120                                 TWIInfo.errorCode = 0xFF;
 121                                 TWISendStart();
 122                         }
 123                         // All transmissions are complete, exit
 124                         else
 125                         {
 126                                 TWIInfo.mode = Ready;
 127                                 TWIInfo.errorCode = 0xFF;
 128                                 TWISendStop();
 129                         }
 130                         break;
 131
 132                 // ----\/ ---- MASTER RECEIVER ----\/ ----  //
 133
 134                 case TWI_MR_SLAR_ACK: // SLA+R has been transmitted, ACK has been received
 135                         // Switch to Master Receiver mode
 136                         TWIInfo.mode = MasterReceiver;
 137                         // If there is more than one byte to be read, receive data byte and return an ACK
 138                         if (RXBuffIndex < RXBuffLen-1)
 139                         {
 140                                 TWIInfo.errorCode = TWI_NO_RELEVANT_INFO;
 141                                 TWISendACK();
 142                         }
 143                         // Otherwise when a data byte (the only data byte) is received, return NACK
 144                         else
 145                         {
 146                                 TWIInfo.errorCode = TWI_NO_RELEVANT_INFO;
 147                                 TWISendNACK();
 148                         }
 149                         break;
 150
 151                 case TWI_MR_DATA_ACK: // Data has been received, ACK has been transmitted.
 152
 153                         /// -- HANDLE DATA BYTE --- ///
 154                         TWIReceiveBuffer[RXBuffIndex++] = TWDR;
 155                         // If there is more than one byte to be read, receive data byte and return an ACK
 156                         if (RXBuffIndex < RXBuffLen-1)
 157                         {
 158                                 TWIInfo.errorCode = TWI_NO_RELEVANT_INFO;
 159                                 TWISendACK();
 160                         }
 161                         // Otherwise when a data byte (the only data byte) is received, return NACK
 162                         else
 163                         {
 164                                 TWIInfo.errorCode = TWI_NO_RELEVANT_INFO;
 165                                 TWISendNACK();
 166                         }
 167                         break;
 168
 169                 case TWI_MR_DATA_NACK: // Data byte has been received, NACK has been transmitted. End of transmission.
 170
 171                         /// -- HANDLE DATA BYTE --- ///
 172                         TWIReceiveBuffer[RXBuffIndex++] = TWDR;
 173                         // This transmission is complete however do not release bus yet
 174                         if (TWIInfo.repStart)
 175                         {
 176                                 TWIInfo.errorCode = 0xFF;
 177                                 TWISendStart();
 178                         }
 179                         // All transmissions are complete, exit
 180                         else
 181                         {
 182                                 TWIInfo.mode = Ready;
 183                                 TWIInfo.errorCode = 0xFF;
 184                                 TWISendStop();
 185                         }
 186                         break;
 187
 188                 // ----\/ ---- MT and MR common ----\/ ---- //
 189
 190                 case TWI_MR_SLAR_NACK: // SLA+R transmitted, NACK received
 191                 case TWI_MT_SLAW_NACK: // SLA+W transmitted, NACK received
 192                 case TWI_MT_DATA_NACK: // Data byte has been transmitted, NACK received
 193                 case TWI_LOST_ARBIT: // Arbitration has been lost
 194                         // Return error and send stop and set mode to ready
 195                         if (TWIInfo.repStart)
 196                         {
 197                                 TWIInfo.errorCode = TWI_STATUS;
 198                                 TWISendStart();
 199                         }
 200                         // All transmissions are complete, exit
 201                         else
 202                         {
 203                                 TWIInfo.mode = Ready;
 204                                 TWIInfo.errorCode = TWI_STATUS;
 205                                 TWISendStop();
 206                         }
 207                         break;
 208                 case TWI_REP_START_SENT: // Repeated start has been transmitted
 209                         // Set the mode but DO NOT clear TWINT as the next data is not yet ready
 210                         TWIInfo.mode = RepeatedStartSent;
 211                         break;
 212
 213                 // ----\/ ---- SLAVE RECEIVER ----\/ ----  //
 214
 215                 // TODO  IMPLEMENT SLAVE RECEIVER FUNCTIONALITY
 216
 217                 // ----\/ ---- SLAVE TRANSMITTER ----\/ ----  //
 218
 219                 // TODO  IMPLEMENT SLAVE TRANSMITTER FUNCTIONALITY
 220
 221                 // ----\/ ---- MISCELLANEOUS STATES ----\/ ----  //
 222                 case TWI_NO_RELEVANT_INFO: // It is not really possible to get into this ISR on this condition
 223                                                                    // Rather, it is there to be manually set between operations
 224                         break;
 225                 case TWI_ILLEGAL_START_STOP: // Illegal START/STOP, abort and return error
 226                         TWIInfo.errorCode = TWI_ILLEGAL_START_STOP;
 227                         TWIInfo.mode = Ready;
 228                         TWISendStop();
 229                         break;
 230         }
 231
 232 }