> I dont know if u can answer me, but i have another two question. What is
the max RAM i can allocate to the samples from PRU, and if is possible to
write directly to an uSDcard working as external
> memory from the PRU. If not, i can do the a discuss about this.

Theoretically, you should be able to access and use all of the ARM's system
memory. Realistically, I'd say you could probably use up to around
300M-400M of the main processors memory. The system needs around ~100M for
processes, and buffering. With all that said, your bottleneck is going to
be the medium you choose to store your samples to. I would avoid the emmc,
as repeated writting / erasing to the emmc would make "short work" of the
emmc. e.g. You'd probably kill the emmc pretty fast. An sdcard will
probably die much quicker.

So the way I see it is that you have two viable options. Some sort of
networked storage, or use an external USB hard drive. Of these two when I
tested this, USB was the fastest option at around 20 Megabytes/second
throughput. The onboard Ethernet is really fast for ethernet at around  ~11
Megabytes / second with the correct tweaks.

Maybe what you really need is a fast C application that grabs the data from
the PRU's memory directly, in real-time, and shuttle that data out just as
fast as you need to. Just off the top of my head, 500ksps will probably be
between 6-7 Megabytes a second, in plain text format. If you dream up some
sort of data packing format, perhaps a good bit less.

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