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High speed ADC to MCU data collection.

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Paptrack:
Hello,

I need to sample a 20MHz signal from an ultrasound transducer. I would need to use a high speed ADC of around 500Msps.

I have searched for MCUs with such a fast ADC but I'm afraid I haven't found any. I will have to use an external ADC like the AD9694, for example. Processing work of the obtained data would be minimal, but I do need to store all conversions in memory (internal or external). The sampling time will last about 2.5ms, so at 500Msps, I would get 1250000samples.

It is the first time I work with such a fast ADC and I am worried about how to store all data fast enough with an MCU. I would like to avoid using an FPGA, as my lack of experience with these devices would greatly extend the project development. AD9694 has an JESD0204B interface but It is being quite difficult to find an MCU with this interface. Should I perhaps choose an ADC with parallel output?

And what about using a DSP? I have no experience with them either and I don't know how difficult is to work with them.

Any suggestion will be welcome. Thank you in advance.

moffy:
I think you need an FPGA, for the interface to the ADC and transfer to memory, the response times and data rates are beyond an MCU, I think DSPs would have the same issues unless one has an integrated FPGA.

moffy:
What you are trying to do is very similar to a digital oscilloscope's digitizing section, they could act as a reference point.

eTobey:
What do you need to measure it for? Distance measurment?

radiolistener:
Usually such ADC stream is processed on FPGA. You can do frequency shift, apply CIC and compensation FIR filter with decimation in order to reduce sample rate and then transfer it to MCU at lower sample rate for further processing. This way is used for realtime continuous stream processing, for example in radio receivers, radars, etc.

But if you're needs to process full bandwidth, then you're needs to attach RAM to FPGA and record sample to the RAM at full ADC speed and then read it with MCU and process it at lower speed. This is how digital oscilloscopes working.

I'm afraid there is no MCU which can do DSP for a stream at 100-200 MS/s speed.

Modern PC can do realtime processing for such fast streams, but there is another problem - to deliver that stream to CPU internal bus, which is also needs to use FPGA.

FT2232HL allows to deliver fast stream from 8-bit parallel bus to PC through USB, but it's speed is limited with 480 MBps, which is not enough to deliver digitized 20 MHz signal.

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