What makes nRF52832 chip voltage drop per 1024 secs ? softdevice or RTC ?

[Daewoong Kim]

Hi,

I've already asked this problem few days ago, but I couldn't figure out the clear answer.

The above figure shows the VDD values of BLE chip. The power supplied by coin cell and VDD values are

measured by SA-ADC in nRF52832 and sent to UART terminal.

Radio module wasn't operated.

The BLE chip was kept in room temperature (25 C).. 

I know that the coin cell has high resistance and this could cause the those voltage drop

However, why this phenomenon occurred periodically??

What makes nRF chip voltage drop every 1024 seconds ??

softdeivce ? or RTC ?

- Thanks for all reply

[haakonsh]

It could be either.

What are your SAADC sample rate and buffer size? Do you store the samples in flash?

What is your RTC doing? 

[Daewoong Kim]

sampling rate is followed by nRF52832 SA-ADC spec, and oversampled (x16) with 12 bits size.

RTC0 is used for softdevice s132-3.1.0 and RTC1 is used for main application with 1000 ms timeout.

The ADC values are not stored in memory. It was just sent to UART terminal (e.g. TeraTerm).

Actually, whether the ADC output value precise or not isn't important.

I just want to know that what makes voltage drops per 1024 seconds...

I thought that RTC0 overflow triggers the voltage drop but the period of RTC0 overflow is 512 seconds..

Maybe no one has observed this situation

[haakonsh]

What is the sample rate of the SAADC?
Are you manually sampling at each sampling period or are you controlling the sampling via a TIMER or RTC?