/**
* \brief Notification of Last byte is transmitted
*
* \param none.
*/
static void twi_slave_last_byte_write_done(void)
{
slave_transfer.state = TWI_IDLE;
slave_transfer.status = TWI_STATUS_TX_COMPLETE;
twi_slave_enable();
}
/**
* \brief Resets the slave state and status to initial for next
* transmission/reception
*/
void twi_slave_status_reset(void)
{
slave_transfer.state = TWI_IDLE;
slave_transfer.status = TWI_STATUS_NO_STATE;
twi_mode = SLAVE;
twi_slave_enable();
}
int main(void) {
// Set clock @ 8Mhz
CPU_PRESCALE(1);
sei();
twi_slave_init();
twi_slave_enable();
for (;;);
}
/**
* \internal
*
* \brief TWI Interrupt Handler
*/
static void twi_interrupt_handler(void)
{
uint8_t status;
status = TWI_TWSR_STATUS_MASK;
switch (status) {
case TWS_START: /*A START condition has been transmitted.*/
case TWS_RSTART: /*A repeated START condition has been
*transmitted.*/
twi_master_start();
break;
case TWS_MT_SLA_ACK: /*SLA+W has been transmitted; ACK has
*been received.*/
case TWS_MT_DATA_ACK: /*Data byte has been transmitted; ACK has
*been received.*/
twi_master_write_done();
break;
case TWS_BUSERROR: /*Bus error due to illegal START or STOP
* condition.*/
case TWS_MT_SLA_NACK: /*SLA+W has been transmitted; NOT ACK has
*been received.*/
case TWS_MT_DATA_NACK: /*Data byte has been transmitted; NOT ACK
*has been received.*/
case TWS_MR_SLA_NACK: /*SLA+R has been transmitted; NOT ACK has
*been received.*/
twi_master_bus_reset();
master_transfer.status = ERR_IO_ERROR;
break;
case TWS_MR_SLA_ACK: /*SLA+R has been transmitted; ACK has been
*received.*/
twi_master_addr_ack();
break;
case TWS_MR_DATA_ACK: /*Data byte has been received; ACK has been
*returned.*/
twi_master_read_done(twi_read_byte());
break;
case TWS_MR_DATA_NACK: /*Data byte has been received; NOT ACK has
*been returned.*/
twi_master_read_last_byte(twi_read_byte());
break;
case TWS_M_ARB_LOST: /*Arbitration lost in SLA+W or data bytes
*(Transmitter); Arbitration lost in SLA+R or
*NOT ACK bit (Receiver).*/
/* If arbitration lost indicate to application to decide either
* switch to Slave mode or wait until the bus is free and transmit
* a new START condition */
master_transfer.state = TWI_IDLE;
master_transfer.status = ERR_BUSY;
twi_master_busy = false;
break;
case TWS_ST_SLA_ACK: /* Own SLA+R has been received; ACK has been
* returned */
case TWS_ST_SLA_ACK_M_ARB_LOST: /* ! Arbitration lost in SLA+R/W as Master;
*own SLA+R has been received;
*ACK has been returned */
slave_transfer.data_count = 0; /* Set buffer pointer to first data
* location */
case TWS_ST_DATA_ACK: /* Data byte in TWDR has been transmitted;
* ACK has been received */
twi_slave_data_write();
slave_transfer.state = TWI_PROCESS;
break;
case TWS_ST_DATA_NACK: /* Data byte in TWDR has been transmitted;
* NACK has been received. */
/* I.e. this could be the end of the
* transmission. */
twi_slave_last_byte_write_done();
break;
case TWS_SR_GEN_ACK: /* General call address has been received;
* ACK has been returned */
case TWS_SR_GEN_ACK_M_ARB_LOST: /* ! Arbitration lost in SLA+R/W as Master;
* General call address has been received;
* ACK has been returned */
case TWS_SR_SLA_ACK: /* Own SLA+W has been received ACK has been
* returned */
case TWS_SR_SLA_ACK_M_ARB_LOST: /* ! Arbitration lost in SLA+R/W as Master;
* own SLA+W has been received;
* ACK has been returned */
slave_transfer.data_count = 0; /* Set buffer pointer to first data
* location */
twi_slave_enable();
slave_transfer.state = TWI_PROCESS;
break;
case TWS_SR_SLA_DATA_ACK: /* Previously addressed with own SLA+W; data
* has been received; ACK has been returned */
case TWS_SR_GEN_DATA_ACK: /* Previously addressed with general call;
* data has been received; ACK has been
* returned */
twi_slave_data_read(twi_read_byte());
slave_transfer.state = TWI_PROCESS;
break;
case TWS_SR_STOP_RESTART: /* A STOP condition or repeated START
* condition has been received while still
* addressed as Slave */
/* Enter not addressed mode and listen to address match */
slave_transfer.state = TWI_IDLE;
slave_transfer.status = TWI_STATUS_RX_COMPLETE;
twi_slave_enable();
break;
case TWS_SR_SLA_DATA_NACK: /* Previously addressed with own SLA+W; data
* has been received; NOT ACK has been
* returned */
case TWS_SR_GEN_DATA_NACK: /* Previously addressed with general call;
* data has been received; NOT ACK has been
* returned */
case TWS_ST_DATA_ACK_LAST_BYTE: /* Last data byte in TWDR has been
* transmitted (TWEA = ; ACK has
* been received */
twi_slave_bus_reset();
slave_transfer.status = TWI_STATUS_IO_ERROR;
break;
default:
if(twi_mode == MASTER)
{
master_transfer.state = TWI_IDLE;
master_transfer.status = ERR_PROTOCOL;
twi_master_busy = false;
}
else
{
slave_transfer.status = TWI_STATUS_PROTOCOL_ERROR; /* Store TWI State as
* errormessage, operation also
* clears the Success bit */
slave_transfer.state = TWI_IDLE;
twi_slave_enable();
}
break;
}
}
/**
* \brief Read received data
*
* \param data - Contains data read from twi bus to be written to data receive
*buffer.
*/
static void twi_slave_data_read(uint8_t data)
{
slave_transfer.data_buffer->rx_buffer[slave_transfer.data_count++] = data;
twi_slave_enable();
}
/**
* \brief writing an byte to TWI.
*
* \param data - contains the data to transmitted ro master.
*/
static inline void twi_slave_write_byte(uint8_t data)
{
TWDR = data;
twi_slave_enable();
}
