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Need help on Periph_to_mem DMA transfer started from an interrupt

Question asked by di_Bene.Alberto on May 15, 2013
Latest reply on May 1, 2015 by tag.aseok

I need advice on the following problem.

I have to connect an external hardware generating 32-bit values at a continuous rate of 1536 kHz to a GPIO port of a Cortex M4F CPU, that of the STM32F4 Discovery board, which I am using as a proof of concept before committing for the production of the final PCB.

I had thought to use the DMA to fill a 512-entry buffer, in double buffered mode, alerting the CPU when one of the two flip-flop buffers is filled. This seems to not present problems.

What I am not sure is how to communicate to the DMA controller that a new sample is ready on the GPIO port. First of all, can the DMA be used this way ? IOW, can it be controlled by an EXTI interrupt generated by a pin of a GPIO port (of course not the same port where the samples are arriving from).

To summarize, the flow should be this :

- A new 32-bit sample is set on the pins of a GPIO port.
- A pin of another port is toggled to tell to the DMA controller to read that value and to deposit it in  memory, incrementing the memory address.
- When the count of samples reaches 512, a buffer switch happens, and an interrupt is generated to the CPU, which will then process the just filled buffer.

So what I need is a way to trigger a DMA request by toggling a pin of a GPIO port. Is this possible ?

A snippet of code on how to initialize the NVIC and the DMA controllers would be much appreciated, thanks.