nrf52832 constantly consuming higher current of 3.4ma after reading adc value using using saadc in blocking mode

RE: nrf52832 constantly consuming higher current of 3.4ma after reading adc value using using saadc in blocking mode

Kenneth — Wed, 11 Jan 2023 21:52:22 GMT

I noticed your calculation were likely using the FPU, so just wanted to make sure the problem was not related to this errata:
https://infocenter.nordicsemi.com/topic/errata_nRF52832_Rev2/ERR/nRF52832/Rev2/latest/anomaly_832_87.html

Kenneth

RE: nrf52832 constantly consuming higher current of 3.4ma after reading adc value using using saadc in blocking mode

harid — Wed, 11 Jan 2023 12:38:55 GMT

Yes, the nrf_pwr_mgmt_run() is called from the main() which implements PWR_MGMT_FPU_SLEEP_PREPARE(). May I know why does this impact current consumption of ADC peripheral?

RE: nrf52832 constantly consuming higher current of 3.4ma after reading adc value using using saadc in blocking mode

Kenneth — Mon, 09 Jan 2023 12:36:47 GMT

Maybe the SAADC is not the problem here, what does you sleep routine look like? Do you for instance include the PWR_MGMT_FPU_SLEEP_PREPARE() before going to sleep?

Kenneth

RE: nrf52832 constantly consuming higher current of 3.4ma after reading adc value using using saadc in blocking mode

harid — Mon, 09 Jan 2023 12:12:39 GMT

But I am not enabling the EasyDMA in the first place. Then how is it possible for EasyDMA channel to be active? And I am using blocking mode to read adc value from saadc.

RE: nrf52832 constantly consuming higher current of 3.4ma after reading adc value using using saadc in blocking mode

Kenneth — Mon, 09 Jan 2023 12:07:30 GMT

Hello,

You may find this example useful as refeence:
https://github.com/NordicPlayground/nRF52-ADC-examples/tree/master/nrfx_saadc_simple_low_power_app_timer_multichannel_oversample

The likely cause of increased current when using SAADC is if EasyDMA channel is active between SAADC and RAM. The SAADC peripheral keep easyDMA channel to RAM active (which consume current) until the SAADC peripheral is stopped or finished (endevent):

"The EasyDMA will have finished accessing the RAM when the END or STOPPED event has been generated."
https://infocenter.nordicsemi.com/topic/com.nordic.infocenter.nrf52832.ps.v1.1/saadc.html#saadc_easydma

Best regards,
Kenneth

RE: nrf52832 constantly consuming higher current of 3.4ma after reading adc value using using saadc in blocking mode

harid — Mon, 09 Jan 2023 09:18:50 GMT

Hi Khawaja,

I tried enabling the recommended macro and also SAADC_CONFIG_LP_MODE. Enabling both of them doesn't seem to be making a difference. Still I am seeing a constant 3.4ma current consumption after reading adc value once and deinitializing adc peripheral. Once deinitiliazed, the current consumption should drop down to 70ua right? Its not the case here. I am taking an average of 200 samples at a time to calculate battery percentage by measuring the battery voltage.

RE: nrf52832 constantly consuming higher current of 3.4ma after reading adc value using using saadc in blocking mode

Khawaja — Mon, 09 Jan 2023 08:44:22 GMT

Have you checked wether low power Saadc mode enabled in config or not? Macro for low power Saadc is
NRFX_SAADC_CONFIG_LP_MODE - Enabling low power mode

The difference between the low-power mode and normal mode is that in low-power mode the START task is not triggered until the sample function is called, while in normal mode, START task is triggered when the buffer_convert function is called to setup the buffers. The SAADC peripheral support EasyDMA, allowing sampling of channels directly to RAM using PPI, without CPU intervention. When low-power mode is enabled, the CPU is required to trigger sampling, and it will only work with a buffer size of 1 sample. In case of high sample rate, there is little or no benefit from the low-power mode. The low-power mode is implemented exactly for the scenario that you describe.

I hope it helps.