High power after starting SAADC and softdevice

RE: High power after starting SAADC and softdevice

MartinBL — Wed, 25 Jul 2018 16:50:51 GMT

Hi,

I'm glad you figured out a solution.

When you use two (or more) buffers the SAADC driver utilizes EasyDMA to be able to take multiple samples without bothering your CPU with interrupts for each sample. EasyDMA requires certain HW resources, like e.g. the HF clock, to work and these resources draw more current.

RE: High power after starting SAADC and softdevice

lbe — Tue, 24 Jul 2018 13:40:30 GMT

Hi Martin, thanks for your reply.

I found a solution and it was not the logger module; it is not clear to me but maybe you can understand why this is working.

In my original post I forgot to mention that I was using 2 channels and a double buffer: following indications here in the forum, I was using one buffer for one channel and the other one for the second channel.

It turned out that for some reason the double buffering was causing the extra consumption. I now use a single buffer and I initialize the saadc to measure a first time from one channel and inside the saadc_callback I re-initialize the saadc to measure from the second channel (I use a shared variable to select first a channel then the other).

It is not important for my application to have both values at exactly the same time, so this solution is fine for me.

In any case, even if it works, I am curious to understand why the double buffer causes an extra consumption....do you have any idea about this?

RE: High power after starting SAADC and softdevice

MartinBL — Tue, 24 Jul 2018 13:24:36 GMT

Hi,

Yes, that is probably the HFCLK running. Have you enabled the Logger module? It is also known to draw ~500 uA. Can you share your project files?