S110 Soft Device and Analog Inputs

[Jarmo]

I have an application that reads an nRF51822 pin configured as analog input and then sends that value using "ble uart" (included in Nordic's sdk). Analog input is read in an interrupt 250 times per second, but only a few of those values are sent from my main loop (not from interrupt). However, when the connection is established, the analog input stops working but just gives a fixed value (218).

The problem can be solved by initializing analog input in my main loop all the time as follows:

nrf_adc_init(ADC_RES_10bit, ADC_INPUT_AIN3_P02, ADC_INT_DISABLED);

But if I do so, then the BTLE connection hangs up within a half a minute, and actually the whole system probably crashes.

How should I handle ADC when using soft device? Is the soft device using ADC in some way?

[Jarmo]

Thanks for all replies! Now it looks like the problem with ADC might be here:

uint32_t nrf_adc_read(void) { uint32_t adc_data; NRF_ADC->TASKS_START = 1; while(NRF_ADC->EVENTS_END == 0); // note the loop! NRF_ADC->EVENTS_END = 0; adc_data = NRF_ADC->RESULT; return adc_data; }

I am using the above function from an interrupt running 250 times a second. At the same time there is S110 BLE connection ("UART" ) active and I am sending data over that. It is done in the main loop and not from interrupt, indeed. Also, the data is printed out using wired UART.

The system works from ten seconds to several minutes before getting stuck. I have been debugging this issue now several days and finally found a modification that seems to solve the issue: when I comment away the while() -loop in the above function the stucking does not happen any more (at least it hasn't been happening yet).

// while(NRF_ADC->EVENTS_END == 0); // it seems that stucking happens here?!?

Any explanations for this behaviour?