RE: DMA power usage and start from sleep time question

colin_was_here — Wed, 18 Nov 2020 22:57:16 GMT

Thanks for the reply, sorry I just got back to this..

So I guess I'm wondering if you've gotten the dma to use less than 1.2ma while on? If you roam around the forums you can find lots of people having the same issue...

Luckily a coworker of mine found this low power saadc example-which conveniently isn't in the sdk, which boots up on the rtc, takes one sample then goes to bed, the dma is only on during the one sample I guess. so that's good.. I think this will be much better..

RE: DMA power usage and start from sleep time question

Dmitry — Sat, 14 Nov 2020 09:59:57 GMT

Hi,

[quote userid="95627" url="~/f/nordic-q-a/68348/dma-power-usage-and-start-from-sleep-time-question"] I'm pretty sure somethings broken[/quote]

Yes, definitely something is broken.. we can guess what exactly, but with source code it would be much faster :) 1.2mA looks like always-on HFCLK due to some peripheral is working all the time (DCDC is not enabled, right?)

[quote userid="95627" url="~/f/nordic-q-a/68348/dma-power-usage-and-start-from-sleep-time-question"]the whole point of dma is to save power no?[/quote]

The whole point of dma is to offload byte-copying task from cpu, so it won't wake up and go through ISR just to write one byte. Yes, it shorten the peaks but shouldn't change current in sleep mode.

[quote userid="95627" url="~/f/nordic-q-a/68348/dma-power-usage-and-start-from-sleep-time-question"]I can't find it in the datasheet anywhere, does anyone have any idea if this would be better or worse than the dma??[/quote]

I think, even an irq-driven solution is better (wake-up by interrupt is faster than full booting)