/**
* \brief Enable NACK transfer in Slave Receive Mode
*
* \param twis Base address of the TWI (i.e. &AVR32_TWIS).
* \param stop_callback Set true to use Stop condition Callback function
*/
void twis_send_data_nack(volatile avr32_twis_t *twis, bool stop_callback) {
// Send NACK
twis->cr |= AVR32_TWIS_CR_ACK_MASK;
// Disable all interrupts
twis->idr = ~0UL;
// Clear all status
twis->scr = ~0UL;
// Enable Slave Address Match Interrupt
twis->ier = AVR32_TWIS_IER_SAM_MASK;
// If callback is desired, go to the stop condition callback function
if (stop_callback) {
twis_slave_fct.stop();
}
}
/**
* \internal
* \brief TWIS interrupt handler
*/
ISR(twis_slave_interrupt_handler,CONF_TWIS_IRQ_GROUP,CONF_TWIS_IRQ_LEVEL)
{
// Get status and interrupt mask register values
unsigned long status = twis_inst_slave->sr;
unsigned long enabled = twis_inst_slave->imr;
unsigned long pending = status & enabled;
// An error has occurred, set only address match active and return
if (status & AVR32_TWIS_SR_ERROR_MASK) {
twis_inst_slave->idr = ~0UL;
twis_inst_slave->scr = ~0UL;
twis_inst_slave->ier = AVR32_TWIS_IER_SAM_MASK;
twis_slave_fct.stop();
return;
}
// Check if the slave address match flag is raised
if (pending & AVR32_TWIS_IER_SAM_MASK) {
// Ignore repeated start and transmission complete flags
if (pending & (AVR32_TWIS_SR_REP_MASK | AVR32_TWIS_SR_TCOMP_MASK)) {
twis_inst_slave->scr = (AVR32_TWIS_SCR_REP_MASK |
AVR32_TWIS_SCR_TCOMP_MASK);
twis_inst_slave->idr = (AVR32_TWIS_IDR_REP_MASK |
AVR32_TWIS_IDR_TCOMP_MASK);
}
pending &= ~(AVR32_TWIS_SR_REP_MASK | AVR32_TWIS_SR_TCOMP_MASK);
// Enable error handling
twis_inst_slave->ier = AVR32_TWIS_SR_ERROR_MASK;
// Check if the slave should be in receive or transmit mode
if (status & AVR32_TWIS_SR_TRA_MASK) {
// Transmit mode
twis_inst_slave->scr = AVR32_TWIS_SR_BTF_MASK;
twis_inst_slave->ier = AVR32_TWIS_IER_BTF_MASK
| AVR32_TWIS_IER_TCOMP_MASK;
twis_inst_slave->thr = twis_slave_fct.tx();
} else {
// Receive mode
twis_inst_slave->ier = AVR32_TWIS_IER_RXRDY_MASK
| AVR32_TWIS_IER_TCOMP_MASK
| AVR32_TWIS_IER_REP_MASK;
}
}
// Check if there is data ready to be read in the data receive register
if (pending & AVR32_TWIS_IER_RXRDY_MASK) {
// Call user specific receive function
twis_slave_fct.rx(twis_inst_slave->rhr);
}
// Check if the transmit ready flag is raised
if (pending & AVR32_TWIS_SR_BTF_MASK) {
if (status & AVR32_TWIS_SR_NAK_MASK) {
twis_inst_slave->idr = AVR32_TWIS_IDR_BTF_MASK;
twis_inst_slave->scr = AVR32_TWIS_SCR_BTF_MASK;
twis_inst_slave->ier = AVR32_TWIS_IER_TCOMP_MASK
| AVR32_TWIS_IER_REP_MASK;
// Clear the NAK
twis_inst_slave->scr = AVR32_TWIS_SCR_NAK_MASK;
} else {
twis_inst_slave->thr = twis_slave_fct.tx();
}
}
// Check if the transmission complete or repeated start flags raised
if (pending & (AVR32_TWIS_SR_TCOMP_MASK | AVR32_TWIS_SR_REP_MASK)) {
// Clear transmit complete and repeated start flags
twis_inst_slave->scr = AVR32_TWIS_SCR_TCOMP_MASK
| AVR32_TWIS_SCR_REP_MASK;
// Disable transmission ready interrupt
twis_inst_slave->idr = AVR32_TWIS_IDR_BTF_MASK
| AVR32_TWIS_IDR_RXRDY_MASK
| AVR32_TWIS_IDR_TCOMP_MASK
| AVR32_TWIS_IDR_REP_MASK;
// Enable slave address match interrupt
twis_inst_slave->ier = AVR32_TWIS_IER_SAM_MASK;
// Call user specific stop function
twis_slave_fct.stop();
}
/* Never clear the NAK mask without first receiving the appropriate
* BTF bit too.
*
* L4U Errata 38.1.3.2:
* Clearing the NAK bit before the BTF bit is set locks up the TWI bus
* When the TWIS is in transmit mode, clearing the NAK Received (NAK)
* bit of the Status Register (SR) before the end of the
* Acknowledge/Not Acknowledge cycle will cause the TWIS to
* attempt to continue transmitting data, thus locking up the bus.
*
* Fix/Workaround
* Clear SR.NAK only after the Byte Transfer Finished (BTF) bit of the same register has been
* set.
*/
twis_inst_slave->scr = pending & (~AVR32_TWIS_SCR_NAK_MASK);
return;
}
/**
* \internal
* \brief TWIS interrupt handler
*/
ISR(twis_slave_interrupt_handler,CONF_TWIS_IRQ_GROUP,CONF_TWIS_IRQ_LEVEL)
{
// Get status and interrupt mask register values
unsigned long status = twis_inst_slave->sr;
unsigned long enabled = twis_inst_slave->imr;
unsigned long pending = status & enabled;
// An error has occurred, set only address match active and return
if (status & AVR32_TWIS_SR_ERROR_MASK) {
twis_inst_slave->idr = ~0UL;
twis_inst_slave->scr = ~0UL;
twis_inst_slave->ier = AVR32_TWIS_IER_SAM_MASK;
twis_slave_fct.stop();
return;
}
// Check if the slave address match flag is raised
if (pending & AVR32_TWIS_IER_SAM_MASK) {
// Ignore repeated start and transmission complete flags
if (pending & AVR32_TWIS_SR_REP_MASK) {
twis_inst_slave->scr = AVR32_TWIS_SCR_REP_MASK;
}
if (pending & AVR32_TWIS_SR_TCOMP_MASK) {
twis_inst_slave->scr = AVR32_TWIS_SCR_TCOMP_MASK;
}
// Enable error handling
twis_inst_slave->ier = AVR32_TWIS_SR_ERROR_MASK;
// Check if the slave should be in receive or transmit mode
if (status & AVR32_TWIS_SR_TRA_MASK) {
// Transmit mode
twis_inst_slave->scr = AVR32_TWIS_SR_BTF_MASK;
twis_inst_slave->ier = AVR32_TWIS_IER_BTF_MASK
| AVR32_TWIS_IER_TCOMP_MASK;
twis_inst_slave->thr = twis_slave_fct.tx();
} else {
// Receive mode
twis_inst_slave->ier = AVR32_TWIS_IER_RXRDY_MASK
| AVR32_TWIS_IER_TCOMP_MASK
| AVR32_TWIS_IER_REP_MASK;
}
}
// Check if there is data ready to be read in the data receive register
if (pending & AVR32_TWIS_IER_RXRDY_MASK) {
// Call user specific receive function
twis_slave_fct.rx(twis_inst_slave->rhr);
}
// Check if the transmit ready flag is raised
if (pending & AVR32_TWIS_SR_BTF_MASK) {
if (status & AVR32_TWIS_SR_NAK_MASK) {
twis_inst_slave->idr = AVR32_TWIS_IDR_BTF_MASK;
twis_inst_slave->scr = AVR32_TWIS_SCR_BTF_MASK;
twis_inst_slave->ier = AVR32_TWIS_IER_TCOMP_MASK
| AVR32_TWIS_IER_REP_MASK;
// Clear the NAK
twis_inst_slave->scr = AVR32_TWIS_SCR_NAK_MASK;
} else {
twis_inst_slave->thr = twis_slave_fct.tx();
}
}
// Check if the transmission complete or repeated start flags raised
if (pending & (AVR32_TWIS_IER_TCOMP_MASK | AVR32_TWIS_IER_REP_MASK)) {
// Clear transmit complete and repeated start flags
twis_inst_slave->scr = AVR32_TWIS_SCR_TCOMP_MASK
| AVR32_TWIS_SCR_REP_MASK | AVR32_TWIS_SCR_NAK_MASK;
// Disable transmission ready interrupt
twis_inst_slave->idr = AVR32_TWIS_IDR_BTF_MASK
| AVR32_TWIS_IDR_RXRDY_MASK
| AVR32_TWIS_IDR_TCOMP_MASK
| AVR32_TWIS_IDR_REP_MASK;
// Enable slave address match interrupt
twis_inst_slave->ier = AVR32_TWIS_IER_SAM_MASK;
// Call user specific stop function
twis_slave_fct.stop();
}
twis_inst_slave->scr = pending;
return;
}