ADC Result not changing w/respect to Analog input

RE: ADC Result not changing w/respect to Analog input

Jay S. — Tue, 16 Aug 2016 12:24:27 GMT

Thanks stefan, the problem was and the port labeling on the SDK51 board. For example, the analog input labeled P0.04 on the board corresponds to ADC_CONFIG_PSEL_AnalogInput5 (0x20).

RE: ADC Result not changing w/respect to Analog input

Stefan Birnir Sverrisson — Fri, 12 Aug 2016 10:41:17 GMT

Hi Jay

Since the example I provided does not work, I see no other conclusion than that the ADC on your nRF51-DK is damaged. I would recommend to get another nRF51-DK.

To further verify that the ADC is damaged, you can try out the adc_timer_driven_scan_mode example available on Github, which samples on three ADC input pins, and does not use softdevice. Sorry for the lack of documentation on the Github examples, I need to work on that. However, this example should be simple, but if you have questions about it, just ask them directly here

RE: ADC Result not changing w/respect to Analog input

Jay S. — Wed, 10 Aug 2016 13:43:26 GMT

I tried the example above you recommended. The result does not change, it's always 0. I also tried a few different thing such as: 1- changed the ADC input source to internal power supply, that gives correct reading. 2- did no. 1 with ADC ENABLE =0 and ADC ENABLE = 1, the result is still correct. 3. While ADC ENABLE = 1 I can still set an analog port as output and write to it. Seems to me that ADC ENABLE is ineffective.

RE: ADC Result not changing w/respect to Analog input

Jay S. — Mon, 01 Aug 2016 18:14:25 GMT

SDK: nRF5_SDK_11.0.0_89a8197 and SoftDevice: s130_nrf51_2.0.1

RE: ADC Result not changing w/respect to Analog input

Jay S. — Mon, 01 Aug 2016 18:06:45 GMT

I do get ADC interrupts checked it with breakpoint in the code.

RE: ADC Result not changing w/respect to Analog input

Jay S. — Mon, 01 Aug 2016 18:02:29 GMT

I check the result through debugger and also can see it as battery % in nRF HRM over Bluetooth connection.

RE: ADC Result not changing w/respect to Analog input

Stefan Birnir Sverrisson — Mon, 01 Aug 2016 17:39:53 GMT

How are you evaluating your results, via UART or via debugger? Are you surely getting ADC interrupts in ADC interrupt handler?

What SDK version and softdevice version are you using?

RE: ADC Result not changing w/respect to Analog input

Jay S. — Mon, 01 Aug 2016 17:36:56 GMT

Hi SteFan

I also had tried P0.01 and P0.02 before and results were incorrect aslo.

Thanks,

RE: ADC Result not changing w/respect to Analog input

Stefan Birnir Sverrisson — Mon, 01 Aug 2016 17:04:15 GMT

Hi Jay

Your ADC configuration seems to be fine, except that you are sampling on analog input pin 0 which maps to pin P0.26 on the nRF51 IC, which is shared with the input from the low frequency 32kHz crystal, see section 2.2.1 in the nRF51822 PS v3.2. Try to sample from e.g. analog input pin 2, which is pin P0.01 instead, to see if you get better results.

Update 5.8.2016 Below is an example which is ble_app_hrs with nRF51 ADC addon, which hopefully addresses what you are trying to do. The example uses the nrf_drv_adc driver. ADC sampling is triggered from the battery application timer. The ADC driver allocates buffer and throws an event to the application when the buffer is full. The ADC handler takes an average value from the buffer values and also calculates millivolts and battery percentage before transferring the results over BLE.

ble_app_hrs_adc_battery_measurement.zip