Gag.  I always hated dealing with DMA controllers.  
I think I have a solution with the gates.  It is old school but I really don’t 
have to have the Pi do anything but insert that one single bit at an 8 Khz rate.

From: Chuck Macenski 
Sent: Friday, February 23, 2018 12:10 PM
Subject: Re: [AFMUG] OT Raspberry PI

Your other option would be to find a way to setup an internal DMA controller to 
trigger off of an external input. From your clock source, you would trigger 
individual DMAs from a static buffer to GPIO connected to some sort of circuit 
to invert the Mark bits. The DMA controller would loop over the buffer and the 
jitter would be limited to that of your 1.544 MHz reference clock source. For 
Raspberry PI, you might be looking at writing a kernel driver/module assuming 
you can find documentation on the CPU and DMA controllers. Might be easier with 
an STM32 like CPU (small, cheap, and potentially Linux free if you are into 
that sort of thing).  

On Fri, Feb 23, 2018 at 10:35 AM, Bill Prince <> wrote:

  1/4 microsecond is too much jitter?

  I don't think the pi is going to be your solution.


  On 2/22/2018 5:22 PM, Chuck McCown wrote:

    I have about 250 nS of jitter on my output signal. 

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