ADC Conversion using 4096Hz for nRF52832 Chip?

[vishal]

Hello Sir,

We are using nRF52832 chip and Softdevice is S132. Is it possible to sample an analog signal using internal ADC conversion using 4096Hz?. Its look like it does at 3900Hz.

Thanks in Advance..

[Jørgen Holmefjord]

I don't know how you have setup RTC, but you should make sure you do not enable interrupt if you want to trigger the sampling through PPI. You also need to clear the RTC after getting the compare event. This can also be done using PPI. I will edit my answer above with a working main.c file for ble_app_uart__saadc_timer_driven__scan_mode that implement sampling using RTC over PPI. Note that you need to include the nrf_drv_rtc.c source file, and enable RTC in sdk_config.h.

[Jørgen Holmefjord]

You might need to get some better equipment than a multimeter for doing presice measurements of these quickly switching currents. I would recommend the Power Profiler Kit. I did some measurements on the ble_app_uart__saadc_timer_driven__scan_mode code with timer and RTC, and did not see large differences in current (TIMER - RTC). The timer in the example runs on PCLK1M, which gives the timer a run current of 5 µA typical + HFINT Clock run current of 60 µA. The run current of RTC is 0.1 µA typical, pluss run current of LFCLK of 0.25-1 µA. There are some differences here, but compared to the total consumption of the application, this is not the part you should be concerned about. The ~2mA base current of the consumption comes from the EasyDMA current. You should consider if you need such a high sample frequency in your application, or if you could lower this and shut down the SAADC between sampling. This will save you much current.