STM32F7 with 80MSPS external ADC + DMA + external 10ns SRAM

[diverger]

Posted on June 12, 2018 at 10:52

I need to do ADC sample with a 80MSPS. I have two choice:

1. Using FPGA
2. Use STM32F7, attach the ADC to the FMC, and using DMA memory-to-memory

80MSPS is near the limit of the F7's GPIO speed limit (100MHz, right?)  And I never run the DMA at a speed so high, so anyone can give some suggestions? If I can use F7 to achieve my goal?

[AvaTar]

Posted on June 12, 2018 at 10:59

I need to do ADC sample with a 80MSPS. I have two choice:

...

80MSPS is near the limit of the F7's GPIO speed limit (100MHz, right?)

I'm confused. GPIOs don't do any AD conversion. And the ADCs are at least one order of magnitude below.

[LMI2]

Posted on June 12, 2018 at 11:47

There are very fast ADCs available, like 1GHz or more. Have you looked at how they handle the data they create. Application notes or something.

[diverger]

Posted on June 12, 2018 at 11:10

I intend to attach the external ADC to the FMC, and give it clocks to read back the conversion data. So I must take the GPIO speed into consideration.

[AvaTar]

Posted on June 12, 2018 at 11:16

Almost thought so. Of course the task of selecting proper ADCs falls on you.

Sounds like a scope or logic analyzer you are trying to build.

Beside of GPIO speed, I would consider the bus load generated by DMA.

[diverger]

Posted on June 12, 2018 at 11:26

Yes, I'm considering the bus load too. Are there some methods/formulas to help me make a decision?

[AvaTar]

Posted on June 12, 2018 at 11:32

I don't have experience with FMC on the F7, others do.

But assuming parallel output of the ADCs, the use case would be similar to FMC graphic operations, except for reversed direction no source address increment.

[diverger]

Posted on June 12, 2018 at 12:31

Fast ADC is not problem. I doubt if the F7's FMC memory-to-memory DMA can handle this.