You don’t indicate how fast your clock is.  Everything in the PRU is polled, so 
you would have to construct a loop that looks at each pin and makes a 
determination if the clock has changed state.  The PRU operates at 200 MHz and 
has simple instructions, so you would have to calculate how many instructions 
you have for each clock to determine if it is even possible.  Then, of course, 
you have to put the data somewhere.   Typically one PRU is used to poll I/O 
lines and assemble the data into chunks that are passed to the 2nd PRU which 
can either put them in ARM DDR memory, send out, etc.  If you get the voltages 
on the PRU input pins correct and the data rate is within what the PRU can 
handle, then this can be done.

 

From: [email protected] <[email protected]> On Behalf Of 
PAk Ys
Sent: Tuesday, May 26, 2020 5:50 AM
To: BeagleBoard <[email protected]>
Subject: [beagleboard] Could PRU read this signals?

 

Hello. 

I am quite new to PRU, sorry in advance if I make any mistake or incorrect 
asumption.

 

I would need to read a LVDS signal which is a 4 data channels + CLK and 
Framesync, that looks like this:

 

  
<https://lh3.googleusercontent.com/proxy/foESJGaSEw6kTwy5LLfdq06HTuj0akr69C8czYlac7iyY5hGqNDZPuWjUD2nnwC5FxoLOxm77EW4CAEXR4U5EU_s7VFA8ZcmENg01jXPP1Svu2YyKrECyHneE_7SABUZKyhGGAal1woc4Ve1zL1UFe478ju20qYfCYKvMekSGWXW=w5000-h5000>
 

 

As you can see, the signals change in every edge (both falling and rising 
edges). 

Of course, we would place a differential LVDS driver receptor prior to the 
beaglebone pru ports (so signal will be exactly as the black + traces in the 
figure). Our intention is to send them later to memory and probably the ARM 
would create a UDP packet to send them over ethernet.

 

I would like to know if there is a way to receive these signals with the PRU in 
any way and process them correctly.

Would it be a Direct Connection Mode configuration?

 

If not would it be possible to make a fast polling on the CLK  & FRAME signals, 
and in every change read/sample the other 4 channels simultaneously?

 

Thank you all.

 

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