diff options
Diffstat (limited to 'drivers/avr/TWIlib.c')
| -rw-r--r-- | drivers/avr/TWIlib.c | 232 |
1 files changed, 232 insertions, 0 deletions
diff --git a/drivers/avr/TWIlib.c b/drivers/avr/TWIlib.c new file mode 100644 index 000000000..b39e3054a --- /dev/null +++ b/drivers/avr/TWIlib.c @@ -0,0 +1,232 @@ +/* + * TWIlib.c + * + * Created: 6/01/2014 10:41:33 PM + * Author: Chris Herring + * http://www.chrisherring.net/all/tutorial-interrupt-driven-twi-interface-for-avr-part1/ + */ + +#include <avr/io.h> +#include <avr/interrupt.h> +#include "TWIlib.h" +#include "util/delay.h" + +void TWIInit() +{ + TWIInfo.mode = Ready; + TWIInfo.errorCode = 0xFF; + TWIInfo.repStart = 0; + // Set pre-scalers (no pre-scaling) + TWSR = 0; + // Set bit rate + TWBR = ((F_CPU / TWI_FREQ) - 16) / 2; + // Enable TWI and interrupt + TWCR = (1 << TWIE) | (1 << TWEN); +} + +uint8_t isTWIReady() +{ + if ( (TWIInfo.mode == Ready) | (TWIInfo.mode == RepeatedStartSent) ) + { + return 1; + } + else + { + return 0; + } +} + +uint8_t TWITransmitData(void *const TXdata, uint8_t dataLen, uint8_t repStart) +{ + if (dataLen <= TXMAXBUFLEN) + { + // Wait until ready + while (!isTWIReady()) {_delay_us(1);} + // Set repeated start mode + TWIInfo.repStart = repStart; + // Copy data into the transmit buffer + uint8_t *data = (uint8_t *)TXdata; + for (int i = 0; i < dataLen; i++) + { + TWITransmitBuffer[i] = data[i]; + } + // Copy transmit info to global variables + TXBuffLen = dataLen; + TXBuffIndex = 0; + + // If a repeated start has been sent, then devices are already listening for an address + // and another start does not need to be sent. + if (TWIInfo.mode == RepeatedStartSent) + { + TWIInfo.mode = Initializing; + TWDR = TWITransmitBuffer[TXBuffIndex++]; // Load data to transmit buffer + TWISendTransmit(); // Send the data + } + else // Otherwise, just send the normal start signal to begin transmission. + { + TWIInfo.mode = Initializing; + TWISendStart(); + } + + } + else + { + return 1; // return an error if data length is longer than buffer + } + return 0; +} + +uint8_t TWIReadData(uint8_t TWIaddr, uint8_t bytesToRead, uint8_t repStart) +{ + // Check if number of bytes to read can fit in the RXbuffer + if (bytesToRead < RXMAXBUFLEN) + { + // Reset buffer index and set RXBuffLen to the number of bytes to read + RXBuffIndex = 0; + RXBuffLen = bytesToRead; + // Create the one value array for the address to be transmitted + uint8_t TXdata[1]; + // Shift the address and AND a 1 into the read write bit (set to write mode) + TXdata[0] = (TWIaddr << 1) | 0x01; + // Use the TWITransmitData function to initialize the transfer and address the slave + TWITransmitData(TXdata, 1, repStart); + } + else + { + return 0; + } + return 1; +} + +ISR (TWI_vect) +{ + switch (TWI_STATUS) + { + // ----\/ ---- MASTER TRANSMITTER OR WRITING ADDRESS ----\/ ---- // + case TWI_MT_SLAW_ACK: // SLA+W transmitted and ACK received + // Set mode to Master Transmitter + TWIInfo.mode = MasterTransmitter; + case TWI_START_SENT: // Start condition has been transmitted + case TWI_MT_DATA_ACK: // Data byte has been transmitted, ACK received + if (TXBuffIndex < TXBuffLen) // If there is more data to send + { + TWDR = TWITransmitBuffer[TXBuffIndex++]; // Load data to transmit buffer + TWIInfo.errorCode = TWI_NO_RELEVANT_INFO; + TWISendTransmit(); // Send the data + } + // This transmission is complete however do not release bus yet + else if (TWIInfo.repStart) + { + TWIInfo.errorCode = 0xFF; + TWISendStart(); + } + // All transmissions are complete, exit + else + { + TWIInfo.mode = Ready; + TWIInfo.errorCode = 0xFF; + TWISendStop(); + } + break; + + // ----\/ ---- MASTER RECEIVER ----\/ ---- // + + case TWI_MR_SLAR_ACK: // SLA+R has been transmitted, ACK has been received + // Switch to Master Receiver mode + TWIInfo.mode = MasterReceiver; + // If there is more than one byte to be read, receive data byte and return an ACK + if (RXBuffIndex < RXBuffLen-1) + { + TWIInfo.errorCode = TWI_NO_RELEVANT_INFO; + TWISendACK(); + } + // Otherwise when a data byte (the only data byte) is received, return NACK + else + { + TWIInfo.errorCode = TWI_NO_RELEVANT_INFO; + TWISendNACK(); + } + break; + + case TWI_MR_DATA_ACK: // Data has been received, ACK has been transmitted. + + /// -- HANDLE DATA BYTE --- /// + TWIReceiveBuffer[RXBuffIndex++] = TWDR; + // If there is more than one byte to be read, receive data byte and return an ACK + if (RXBuffIndex < RXBuffLen-1) + { + TWIInfo.errorCode = TWI_NO_RELEVANT_INFO; + TWISendACK(); + } + // Otherwise when a data byte (the only data byte) is received, return NACK + else + { + TWIInfo.errorCode = TWI_NO_RELEVANT_INFO; + TWISendNACK(); + } + break; + + case TWI_MR_DATA_NACK: // Data byte has been received, NACK has been transmitted. End of transmission. + + /// -- HANDLE DATA BYTE --- /// + TWIReceiveBuffer[RXBuffIndex++] = TWDR; + // This transmission is complete however do not release bus yet + if (TWIInfo.repStart) + { + TWIInfo.errorCode = 0xFF; + TWISendStart(); + } + // All transmissions are complete, exit + else + { + TWIInfo.mode = Ready; + TWIInfo.errorCode = 0xFF; + TWISendStop(); + } + break; + + // ----\/ ---- MT and MR common ----\/ ---- // + + case TWI_MR_SLAR_NACK: // SLA+R transmitted, NACK received + case TWI_MT_SLAW_NACK: // SLA+W transmitted, NACK received + case TWI_MT_DATA_NACK: // Data byte has been transmitted, NACK received + case TWI_LOST_ARBIT: // Arbitration has been lost + // Return error and send stop and set mode to ready + if (TWIInfo.repStart) + { + TWIInfo.errorCode = TWI_STATUS; + TWISendStart(); + } + // All transmissions are complete, exit + else + { + TWIInfo.mode = Ready; + TWIInfo.errorCode = TWI_STATUS; + TWISendStop(); + } + break; + case TWI_REP_START_SENT: // Repeated start has been transmitted + // Set the mode but DO NOT clear TWINT as the next data is not yet ready + TWIInfo.mode = RepeatedStartSent; + break; + + // ----\/ ---- SLAVE RECEIVER ----\/ ---- // + + // TODO IMPLEMENT SLAVE RECEIVER FUNCTIONALITY + + // ----\/ ---- SLAVE TRANSMITTER ----\/ ---- // + + // TODO IMPLEMENT SLAVE TRANSMITTER FUNCTIONALITY + + // ----\/ ---- MISCELLANEOUS STATES ----\/ ---- // + case TWI_NO_RELEVANT_INFO: // It is not really possible to get into this ISR on this condition + // Rather, it is there to be manually set between operations + break; + case TWI_ILLEGAL_START_STOP: // Illegal START/STOP, abort and return error + TWIInfo.errorCode = TWI_ILLEGAL_START_STOP; + TWIInfo.mode = Ready; + TWISendStop(); + break; + } + +} |