AM6442: Read ADC from R5 SPL

Benjamin Postma

Part Number: AM6442

Tool/software:

Hello,

I want to read the ADC (one channel) during R5 SPL. Can you give me a hint how to achive this?
My understanding is that I have to request the device using the ti_sci.c firmware driver. Is the device automatically enabled then (clocks / power)?

Afterwards, I think the steps must be configured (only one in my case) and the ADC must be started. I don't want to use interrupts (for complexity reasons), it would be fine for me to wait some time until the data is available.

Can you post an example of how the ADC must be configured and started?

Thanks in advance.

BR Benjamin

4 months ago

0 Nick Saulnier 4 months ago

TI__Guru** 102120 points

Hello Benjamin,

Apologies for the delayed responses here, I am back from vacation.

Can you tell me a bit more about your usecase? e.g.,

what data do you want to read in?

Which core would actually be consuming the ADC data?

Why R5F SPL instead of something later on, like U-Boot proper or Linux itself?

Regards,

Nick

0 Benjamin Postma 3 months ago in reply to Nick Saulnier

Prodigy 60 points

Hi Nick,

no problem. We have several variants of a board. Each variant has a different voltage divider connected to the ADC. We want to load the correct device tree during first boot stage depending of the value of voltage divider.

BR Benjamin

0 Nick Saulnier 3 months ago in reply to Benjamin Postma

TI__Guru** 102120 points

Hello Benjamin,

Got it.

I would expect that controlling the ADC from R5F during SPL is possible. However, we are unable to support that usecase (nobody from TI has validated that they were able to get ADC during SPL working, and then continued validating the code for each software release).

If you are interested in developing the code on your own, I would start with the pointers in this other e2e thread:
https://e2e.ti.com/support/processors-group/processors/f/processors-forum/1389790/am6442-how-to-read-from-adc-in-u-boot-spl