power optimal twi tx/rx

[rookie]

Hi - I am wondering what is the power optimal way to read/write with the TWI module. I do a tx and rx with the TWI interface. I have something like this, from the examples to read data from a i2c supported device:

// read from i2c device

uint16_t timeout = 10000;
nrf_drv_twi_tx();

while((!twi_tx_done) && --timeout); // twi_tx_done is in the twi_handler for NRF_DRV_TWI_XFER_TX event
twi_tx_done = false;

timeout = 10000;
nrf_drv_twi_rx();
while((!twi_rx_done) && --timeout); // twi_rx_done is in the twi_handler for NRF_DRV_TWI_XFER_RX event
twi_rx_done = false;

I am not sure if this is the most optimal way of waiting, since it's in a busy loop. Is there a better way to write this?

[Simonr]

Yes, you can use _WFE(). But we recommend using the idle_state_handle() function which flushes the NRF_LOG and runs nrf_pwr_mgmt_run(). Please see the ...\nRF5_SDK_15.0.0_a53641a\examples\ble_central\ble_app_blinky_c example for reference.

Best regards,

Simon

[rookie]

I know there is an idle state handler in most examples. May I frame my question slightly differently.

If I understand correctly the nrf_drv_twi_tx/nrf_drv_twi_rx calls are non-blocking since a twi handler gets a callback when a tx or rx event is complete. So let's say when I want to read a register, so we do a tx and then an rx. Now until I receive the rx event in the handler I haven't actually received the value correctly. If I want to write an API to read a register where I pass a value that will be filled with the register value, I will have to jump to the twi handler and then back or just simply waitusing a delay which is not efficient. So my question would be do you have any suggestion to write this effectively?