Using DMA on the MCUexpressoIDE with K64F

[GabrielChies]

Good day to you all,

I am currently working on a project that needs high sampling rate for the ADC channels. I intended to use direct memory acces to avoid interrupts at all costs. So far, Ive set a hardware trigger for the ADC and configured only 2 channels for it to read.
Its the DMA part that's making me thug my hair, it seems overcomplicated on MCU expresso. Can somebody help me set a loop to do continuos sampling of the "n" AD channels. I've been taking the AN4590 document as base, but the functions are behaving a lot diferent from what is in the source material.

The EDMA version I am ussing is 2.4.0.
The board is the K64F.

I'd aprecciate if some light could be shed onto this. Thanx

[GabrielChies]

Hello Edwin, thanks for the reply.

I've already looked into the example you have mentioned. It does not use the Peripherals tools and also some functions seem to be different (not compatible) with the version of the SDK i am running.
Should I abbandon the peripherals tool and do the coding by hand? I rather avoid it since the tool is meant to prevent any mistakes if correctly used. Eaguer to listen to your opinion.

Best regards.

[EdwinHz]

Hi @GabrielChies,

What version of the SDK are you using? The latest one is SDK v2.11.0, and I highly recommend you upgrade to that version if you are using an older one.

You should be able to continue development with the Peripherals Tool, although implementing the DMA is not a trivial task to do without a base example. I recommend you check the example code I shared previously and base your Peripherals Tool settings to match the ones from the example code.

BR,
Edwin.

[GabrielChies]

Hi @Edwin,

Yes, the SDK currently in use is v2.11.0. I’ve been following your recommendation and using the provided example to configure the DMA peripheral. I’ve hit a bit of a snag — the code is getting stuck in a while loop — and I haven’t had the time to fully investigate it yet. I plan to debug it tomorrow to understand what’s happening. My initial guess is that it’s related to FreeRTOS concurrency, or more likely, an issue in the code itself.

For context, my goal is to place the process sample function inside a periodic task that reads and filters all ADC data from the output buffer that the DMA conveniently fills. It’s important to avoid interruptions, since there will be many channels being read at a relatively high sampling rate.

Thanks for the input — I really appreciate your help.
Best regards, Gabriel.

[GabrielChies · Accepted solution]

Hi, good day, 

Update:
I've abbandoned the operational system for now and got it to work as I wanted. For anyone facing the same issues, following the attached PDF is a pretty good place to start in order to understan the way edma works. Once it's working it should not be dificult to place the code on the RTOS system.

Also, thank you Edwin, for the support.

Best regards.

[EdwinHz]

Hi @GabrielChies,

You can find an ADC + eDMA example code on the FRDM-K64F SDK called "adc16_continuous_edma". I highly recommend you use this as reference for your application.

BR,
Edwin.