How to read multiple sensors over TWI? (nrf_drv_twi)

RE: How to read multiple sensors over TWI? (nrf_drv_twi)

Ole Bauck — Wed, 09 Dec 2015 10:39:26 GMT

I don't have the full overview of the new app_twi module, but it looks like it does exactly what you need.

RE: How to read multiple sensors over TWI? (nrf_drv_twi)

Sensors — Tue, 08 Dec 2015 16:03:48 GMT

This seemed a little hack-y to me so didn't want to do it that way unless there was no other way. It seems like it'll get very messy however if I have multiple sensors with varying lengths of data to be received.

I haven't looked into it, but would the app_twi abstraction layer work better in my situation?

RE: How to read multiple sensors over TWI? (nrf_drv_twi)

Ole Bauck — Tue, 08 Dec 2015 13:36:43 GMT

nrf_drv_twi_tx(...) will always be followed by an NRF_DRV_TWI_TX_DONE event and nrf_drv_twi_rx(...) will always be followed by an NRF_DRV_TWI_RX_DONE event. Between the function call and the event, no other transactions will be allowed, meaning nrf_drv_twi_tx(...) or nrf_drv_twi_rx(...) will return NRF_ERROR_BUSY.

You will need to handle the multiple sensors in your code. You can set a flag when starting transfer to the sensor and then check it in the TX or RX done events to know what action to do, something like this:

err_code = nrf_drv_twi_tx(...);
APP_ERROR_CHECK(err_code);    //you may want to do something else if NRF_ERROR_BUSY
m_sensor1_xfer_started = true;

And in the NRF_DRV_TWI_TX_DONE event do something like this:

if(m_sensor1_xfer_started)
{
    m_sensor1_xfer_started = false;
    //code for sensor 1 tx done
}