Confusion reading FIFO of max30101 with nrf51

[Muhammad Nabeel]

Hello,

I have configured max30101 with nrf51 and I want to read the fifo of max30101. The fifo can contain 32 samples and the size of each sample could vary from 3-9 bytes depending upon the number of bytes. My question is if I burst read the fifo by specifying the 3x32=96 bytes in data length variable of nrf_drv_rx() function, would I be able to read the all the data?. For more details, I have attached the description of FIFo register. Any help would be greatly appreciated.

Regards

Muhammad Nabeel Tahir

[awneil]

The MAX30101 neither knows nor cares what microcontroller you use - its behaviour will be the same irrespective.

For clarification of the behaviour of Maxim's chip,  you really need to ask Maxim - it has nothing to do with Nordic!

https://maximsupport.microsoftcrmportals.com/en-US/knowledgebase/

https://maximsupport.microsoftcrmportals.com/en-US/support-center/

Have you looked at the resources Maxim provide?

https://www.maximintegrated.com/en/products/interface/sensor-interface/MAX30101.html/tb_tab2

[Muhammad Nabeel]

Thanks for the reply. Yes max30101 would not have issue with any microcontroller. My question was actually about the nrf_drv_rx() function. Does reading data of n bytes lenghth means something like this. This is the snippet of the code of Arduino library written for max30101.

[awneil]

Muhammad Nabeel said:

the nrf_drv_rx() function

I don't see that in your code?

That's not a Nordic SDK function - is it?

[awneil]

awneil said:

That's not a Nordic SDK function

But nrf_drv_twi_rx() is documented here

https://infocenter.nordicsemi.com/topic/com.nordic.infocenter.sdk5.v15.3.0/group__nrf__drv__twi.html#gab135f4b02e2f7dcd8db59f17063617ff

Sadly, the documentation is not very helpful, and it seems to have be just a copy & paste from the _tx function - without updating!

It doesn't really explain what happens if you request more data than the slave is going to send, or vice-versa.

[Muhammad Nabeel]

Sorry for so much ambiguity. The above code in black background is from arduino library. I am using SDK 12.3.0 and the function

// The method I am using to read the FIFO
nrf_drv_twi_tx(&twi_ins, MAX30101_ADDRESS, &MAX30101_FIFODATA, sizeof(MAX30101_FIFODATA), true);
nrf_drv_twi_rx(&twi_ins, MAX30101_ADDRESS, data, 3/*Read only 1 byte*/);
nrf_delay_ms(1);


// Here is the nrf_drv_twi_rx function

ret_code_t nrf_drv_twi_rx(nrf_drv_twi_t const * p_instance,
                          uint8_t               address,
                          uint8_t *             p_data,
                          uint8_t               length)
{
    nrf_drv_twi_xfer_desc_t xfer = NRF_DRV_TWI_XFER_DESC_RX(address, p_data, length);
    return nrf_drv_twi_xfer(p_instance, &xfer, 0);
}

and code is