STM32F769 DMA and Cache Issue

[THIHA KYAW]

Dear ST,

I have the following issues.

I used ADC1 with DMA2_Stream0, ADC3 with DMA2_Stream4.

If I don't enable cache, it works properly.

Once I enable ICache and DCache, ADC readings are not correct.

Please advise me how to make it work.

Thanks.

Regards,

Thiha Kyaw

[T J]

walk it back,

ICache shouldn't make a difference... but faster code...

Are you using delays or RTOS type task switching or statemachine ?

DCache,

Some memory areas cannot use DCache, you may have to move your buffer to another ram area.

so ICache doesn't kill it..... ??

[THIHA KYAW]

Dear TJ,

Thanks for your reply.

I use Keil RTOS.

Should I assign DMA variable to absolute memory address?

But I don't know which memory area is for DCache? I use STM32F769.

Please advise.

Regards,

Thiha Kyaw

[T J]

not sure on the details,

hopefully the professionals will help out there... Guys ?

Can you search on this site ?

DMA not working...

it is not an uncommon issue.

but resolved by moving the buffer to a different memory area by using a compiler directive( I think)

Guys ?

[Tesla DeLorean]

Caching and cache coherency is the staple of computer architecture classes.

Disabling caching in the blanket sense is going to be very damaging to performance.

Review the Data Sheets and Reference Manuals, pay attention to the block diagrams for the core, peripherals and buses.

The DTCMRAM is not cached, other memories/regions can be describe to the MPU so it doesn't cache them.

Finally you can flush and invalidate regions of memory, down to 32-byte granularity using CMSIS functions.

https://community.st.com/s/question/0D50X00009fEYKFSA4/how-do-i-use-halspireceivedma-in-conjunction-with-a-receive-buffer-on-the-stack-and-caching-enabled

[Tesla DeLorean]

>>Guys?

Please don't do this, none of us are paid to be here, or carry others educational needs or workload.

Most of this can be dealt with using the RTFM method, covering the topics at hand and surrounding material.

[AvaTar]

And check the reference manual for memory regions unavailable to DMA, like so-called TCM areas.

This usually fails silently.

[john doe]

check the cube examples for the f769. there's plenty of examples of MPU configuration for various purposes