Calculating Max, Min, Vrms, Vavg etc. on RF analog inputs

[mzeeshanarshad]

Hi,

I'm interested in reading two RF analog signals at 125MHz each and then calculate the following:

For each of the last 0.1 sec data I want to calculate
1. Vmax, Vmin, Vavg and Vrms of each signal
2. Calculate hase difference between the two signals
3. Send 0.1 second results to the PC

My question is can I do this in C code without having to alter the FPGA code, without missing any samples?
Could you please point the way.
Thanks.

Regards,

Shan

[Nils Roos]

The recent Red Pitaya FPGA designs have a module that can (by the looks of it) be used to do the acquisition part of your requirement. I recently wrote some example code how to program it, but I have not yet examined the acquired data to make sure it is correct and complete.

But the second part - doing post-processing on the samples - could be problematic. At full acquisition rate, there is simply not very much processor time available per sample to do calculations. And the samples are stored per dma into uncached regions of the external ram, so you'll have to get them into the cores first, too.

edit: You could, however, do these calcuations in the FPGA - that's the type of workload it is good at. The application would just have to wait on, fetch, and transmit the results in regular intervals.