frequency sampling limit for beaglebone adc

Question

I intend to use the beaglebone to sample a shaped signal of the order of 1 microsec. I need to fit the signal after and therefore i would like to have a sampling rate of let's 10 MHZ. Something that seems feasible with PRU and libpruio. The point is, looking to the adc specifications it seems there is a limit at 200KHz. Is my reasoning correct?

thanks

Answer 1

You'll need additional hardware for a sampling rate of 10 MHz! libpruio isn't designed to work at that speed, as well as the BBB hardware.

The ADC subsystem in the AM335x CPU is clocked at 24 MHz and needs 15 cycles for a sample (14 in continous mode). This leads to a maximum sample rate of 1.6 (1.74) MSamples/s. See SRM, chapter 12 for details.

The problem is to get the samples in to the host memory. I couldn't get this working faster than ~250 kSamples/s (by CPU access - I didn't try DMA).

As long as you don't need more values than the FIFO can hold, you can sample a single line at maximum 1.7 MHz.

BR