int i2c_read(i2c_t *obj, int address, char *data, int length, int stop)
{
// Zero-length RX transfers are not supported. Such transfers cannot
// be easily achieved with TWI peripheral (some dirty tricks would be
// required for this), and they are actually useless (TX can be used
// to check if the address is acknowledged by a slave).
MBED_ASSERT(length > 0);
twi_info_t *twi_info = TWI_INFO(obj);
#if DEVICE_I2C_ASYNCH
if (twi_info->active) {
return I2C_ERROR_BUS_BUSY;
}
#endif
twi_info->start_twi = false;
NRF_TWI_Type *twi = m_twi_instances[TWI_IDX(obj)];
start_twi_read(twi, address);
int result = length;
while (length > 0) {
int byte_read_result = i2c_byte_read(obj, (stop && length == 1));
if (byte_read_result < 0) {
// When an error occurs, return the number of bytes that have been
// received successfully.
result -= length;
// Force STOP condition.
stop = 1;
break;
}
*data++ = (uint8_t)byte_read_result;
--length;
}
if (stop) {
(void)i2c_stop(obj);
}
return result;
}
int i2c_write(i2c_t *obj, int address, const char *data, int length, int stop)
{
twi_info_t *twi_info = TWI_INFO(obj);
bool timeout = false;
uint32_t t0, t1;
#if DEVICE_I2C_ASYNCH
if (twi_info->active) {
return I2C_ERROR_BUS_BUSY;
}
#endif
twi_info->start_twi = false;
NRF_TWI_Type *twi = m_twi_instances[TWI_IDX(obj)];
start_twi_write(twi, address);
// Special case - transaction with no data.
// It can be used to check if a slave acknowledges the address.
if (length == 0) {
nrf_twi_event_t event;
if (stop) {
event = NRF_TWI_EVENT_STOPPED;
nrf_twi_task_trigger(twi, NRF_TWI_TASK_STOP);
} else {
event = NRF_TWI_EVENT_SUSPENDED;
nrf_twi_event_clear(twi, event);
nrf_twi_task_trigger(twi, NRF_TWI_TASK_SUSPEND);
}
t0 = ticker_read(get_us_ticker_data());
do {
if (nrf_twi_event_check(twi, event)) {
break;
}
t1 = ticker_read(get_us_ticker_data());
timeout = (t1 - t0) >= I2C_TIMEOUT_VALUE_US;
} while (!timeout);
uint32_t errorsrc = nrf_twi_errorsrc_get_and_clear(twi);
if (errorsrc & NRF_TWI_ERROR_ADDRESS_NACK) {
if (!stop) {
i2c_stop(obj);
}
return I2C_ERROR_NO_SLAVE;
}
return (timeout ? I2C_ERROR_BUS_BUSY : 0);
}
int result = length;
do {
uint8_t byte_write_result = twi_byte_write(twi, (uint8_t)*data++);
if (byte_write_result != 1) {
if (byte_write_result == 0) {
// Check what kind of error has been signaled by TWI.
uint32_t errorsrc = nrf_twi_errorsrc_get_and_clear(twi);
if (errorsrc & NRF_TWI_ERROR_ADDRESS_NACK) {
result = I2C_ERROR_NO_SLAVE;
} else {
// Some other error - return the number of bytes that
// have been sent successfully.
result -= length;
}
} else {
result = I2C_ERROR_BUS_BUSY;
}
// Force STOP condition.
stop = 1;
break;
}
--length;
} while (length > 0);
if (stop) {
(void)i2c_stop(obj);
}
return result;
}
uint8_t i2c_active(i2c_t *obj)
{
nrf_drv_twi_t const *twi = &m_twi_instances[TWI_IDX(obj)];
return nrf_drv_twi_is_busy(twi);
}
