PWM Anomaly: nRF52832 vs nRF52833

RE: PWM Anomaly: nRF52832 vs nRF52833

Susheel Nuguru — Mon, 04 Mar 2024 06:26:45 GMT

Hugh. Got your details in linkedin. I think since this is very limited sampling, we might need NDA. Craig, Frey will reach you out in email for the formalities and when it is done, I can send a request to github admin to give you access.

RE: PWM Anomaly: nRF52832 vs nRF52833

hmolesworth — Fri, 01 Mar 2024 13:51:49 GMT

Thanks; sent via LinkedIn

RE: PWM Anomaly: nRF52832 vs nRF52833

Susheel Nuguru — Fri, 01 Mar 2024 12:54:53 GMT

Can you please share your email and github username.

I will have to go through the request internally and will add access to nRF54 resources once I get a green light (which most like is ok).

RE: PWM Anomaly: nRF52832 vs nRF52833

hmolesworth — Fri, 01 Mar 2024 12:49:05 GMT

Thanks Susheel; I'll mull this one over. Meanwhile maybe you could add me to the nRF54 early developers; I have a client wanting me to evaluate an application by testing some hardware.

RE: PWM Anomaly: nRF52832 vs nRF52833

Susheel Nuguru — Fri, 01 Mar 2024 08:15:00 GMT

Hugh,

I got some information and yes there is a change in nRF52833 compared in nRF52832.

There is now a two stage AMLI bus system in nRF52833 instead of one (nRF52832). The reason we did not publish this is because we thought there should be no use cases where the application should directly see the difference. But you genius found the right use case with the right peripheral (PWM) where multi instance trigger at the same time is normal.

So the change is effective to all peripherals with EasyDMA using the 16MHz clock. Not sure if I can give you more but If you want to dive in even more than that, we need to make this ticket private.

RE: PWM Anomaly: nRF52832 vs nRF52833

Susheel Nuguru — Thu, 29 Feb 2024 07:47:46 GMT

Hugh, Haven't forgotten you but it is taking more time than anticipated to investigate this. Just letting you know that this is in my watch list to be part in the internal investigation.

RE: PWM Anomaly: nRF52832 vs nRF52833

Susheel Nuguru — Wed, 21 Feb 2024 06:29:38 GMT

Thanks for the update Hugh, I have updated my query to the peripheral digital team that this is visible in common mode as well. Waiting for someone to pick the ticket and investigate internally in R&D team.

RE: PWM Anomaly: nRF52832 vs nRF52833

hmolesworth — Tue, 20 Feb 2024 11:23:29 GMT

Ok, thanks. Note I edited my last post: Common exhibits the same issue as Grouped on the nRF52833, I thought it was different but I was on the nRF52832 board which does not.

RE: PWM Anomaly: nRF52832 vs nRF52833

Susheel Nuguru — Tue, 20 Feb 2024 05:43:35 GMT

Hugh, It seems different behavior on how EasyDMA trasanctions are placed and prioritized. Seems like something undocumented. I have raised internal query about this to the peripheral digital team, hope to get an answer soon.

RE: PWM Anomaly: nRF52832 vs nRF52833

hmolesworth — Tue, 20 Feb 2024 00:51:44 GMT

Thanks Susheel. Further testing shows this issue applies to PWM Grouped Mode, which I am using to get differential outputs using 2 pins on each of the 4 PWMs. Single output mode using PWM Common Mode and a single output pin does not also exhibits this issue on the nRF52833.

In Grouped Mode (2 x 16-bit DMA transfer), as with Common Mode (1 x 16-bit DMA transfer), I would expect a single 32-bit DMA transfer with unused bits discarded, but maybe that is different from the nRF52832

RE: PWM Anomaly: nRF52832 vs nRF52833

Susheel Nuguru — Mon, 19 Feb 2024 10:04:32 GMT

[quote user=""]My questions: Why is the nRF52832 PWM different from the nRF52833 PWM? Are other peripherals affected in a similar manner? Will any other higher-priority Bus Master such as SPIM re-introduce a phase delay if active at the PPI trigger instant?[/quote]

This most likely will spawn into an internal investigation from the R&D team to reply why we see a difference here. I will create an internal ticket and will update this thread when I get a response from hardware team.