How much?

From: Colin Stanners 
Sent: Thursday, February 22, 2018 5:21 PM
To: af@afmug.com 
Subject: Re: [AFMUG] OT Raspberry PI

I found these devices that do what you want, but they look fancy and expensive, 
I'm guessing that you wish to get around the latter.

https://www.engageinc.com/products/tdm/prima-stratum-gps-stratum-1-clock.html   
 https://www.endruntechnologies.com/gps-frequency-standard.htm


On Thu, Feb 22, 2018 at 5:29 PM, <ch...@wbmfg.com> wrote:

  The problem is there is a crap ton of stuff out there that needs network 
sync.  And it all has a T1 as an input.
  But most T1 trunking circuits are getting replaced with SIP.

  So, I am building a cheap and dirty T1 signal generator that is GPS and 
rhubidium referenced.  The hard part is easy.  The easy part should be easy but 
all the T1 framing chips that used to exist no longer exist.

  The ones that are out there have massive CPU interfaces and tons of registers 
that need to get set to get them fired up and running....

  Where is Exar when you need them....

  From: Adam Moffett 
  Sent: Thursday, February 22, 2018 4:21 PM
  To: af@afmug.com 
  Subject: Re: [AFMUG] OT Raspberry PI

  Tell whoever's got the T1 that 1967 is way behind us and get a new interface.
  Problem eliminated LOL


  ------ Original Message ------
  From: ch...@wbmfg.com
  To: af@afmug.com
  Sent: 2/22/2018 6:16:45 PM
  Subject: Re: [AFMUG] OT Raspberry PI

    I have to generate an alternate mark inversion signal on 1.544 MHz with 
every 193rd bit following a t1 framing sequence.
    Sure wish a 555 could do that.  

    From: Dave 
    Sent: Thursday, February 22, 2018 4:10 PM
    To: af@afmug.com 
    Subject: Re: [AFMUG] OT Raspberry PI

    Find a 555 timer ... I used many in the olden day when radioshacks were 
king LOL!



    On 02/22/2018 05:05 PM, ch...@wbmfg.com wrote:

      I am thinking of using some shift registers instead of using the PI 
output directly as the timing signal. 

      Use the PI to load them.  

      I love me some hardware design anyhow....


      From: Colin Stanners 
      Sent: Thursday, February 22, 2018 3:59 PM
      To: af@afmug.com 
      Subject: Re: [AFMUG] OT Raspberry PI

      Other than setting the process priority, you may need a custom kernel. 
See 
https://medium.com/@metebalci/latency-of-raspberry-pi-3-on-standard-and-real-time-linux-4-9-kernel-2d9c20704495
 


      On Feb 22, 2018 4:48 PM, <ch...@wbmfg.com> 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.  


    -- 

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