No, I saw it, but I already had the Pi so I ignored it and hoped for the best.
I tried it first with arduino.  Just not enough speed.  And it had the jitter 
problem too.

I have a method using three TTL/CMOS chips that is going to work... I think...

The only thing separating the gps disciplined signal and the T1 will be a D 
flip flop and a few AND/NAND gates.  So that ought to get me super low jitter.  

Trying for stratum I with rubidium hold-over isochronous performance at the end 
of the day.  For cheap.

From: Forrest Christian (List Account) 
Sent: Thursday, February 22, 2018 6:27 PM
To: af 
Subject: Re: [AFMUG] OT Raspberry PI

Ok, I think you missed this portion of my email last time:

"I'm skeptical that you'll be able to generate a bitstream with enough accuracy 
under Linux, without extreme programming measures.
I'd suggest a digilent chipkit wifire and the arduino ide for this.  You should 
be able to bitbang at least a T1 with this processor (500mhz)"

Generally the raspberry pi is great for 'tiny server stuff', or 'user 
interface' stuff, and the arduino and/or microcontrollers will work better for 
what you're looking at, since there isn't an operating system in the way.  All 
arduino really is is a c++ ide with some simplified libraries. 

The wifire product I mentioned is really a PIC32MZ dev board, optimized for 
arduino.  If you've had enough of the arduino ide, you can download the 
microchip ide and program it with a full development kit.

Honestly for what you are talking about a EUSART in even a low end PIC might be 
able to handle this.  If you program the EUSART into synchronous mode you'll 
just have to stuff a byte into it every 8 bit times and it will clock it out 
for you.  Not sure if the clock rate is adjustable enough for you, but if you 
get a PIC with the NCO peripheral you might be able to dynamically adjust the 
frequency enough to make it work. 

NCO app sheet:

On Thu, Feb 22, 2018 at 3:48 PM, <> wrote:

  Anyone know how to get my program to run on bare metal?

  Or at the very least tell Linux that my program is the most important thing 
in the world and service it above all other things.

  I am trying to create a timing signal with the Pi.  It is doing it but the 
jitter is pretty bad.  

  I have researched trying to use an interrupt but there is a pretty low limit 
on how many times per second you can fire a hardware interrupt.
  Too low for my application.  


      Forrest Christian CEO, PacketFlux Technologies, Inc.

      Tel: 406-449-3345 | Address: 3577 Countryside Road, Helena, MT 59602 |


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