My memory just reminded me that many of these FPGA's also have some really sophisticated clock synthesis/management blocks. Like it would not surprise me that one of them could generate a jitter free 1.544Mhz clock from say a 10Mhz reference clock out of a Rb oscillator.
On Thu, Feb 22, 2018 at 9:48 PM, Chuck Macenski <ch...@macenski.com> wrote: > This calls out for an FPGA solution. > > On Thu, Feb 22, 2018 at 10:45 PM, Forrest Christian (List Account) < > li...@packetflux.com> wrote: > >> You can get a fpga board which might be suitable for this project (after >> adding appropriate clocks) for around $20 anymore. One example: >> http://tinyfpga.com/ >> >> >> >> On Thu, Feb 22, 2018 at 6:42 PM, Lewis Bergman <lewis.berg...@gmail.com> >> wrote: >> >>> They aren't cheap but you could always use an fpga. >>> >>> On Thu, Feb 22, 2018, 7:35 PM Chuck McCown <ch...@wbmfg.com> wrote: >>> >>>> 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: http://ww1.microchip.com/downl >>>> oads/en/AppNotes/90003131A.pdf >>>> >>>> >>>> >>>> >>>> On Thu, Feb 22, 2018 at 3:48 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. >>>>> >>>> >>>> >>>> >>>> -- >>>> *Forrest Christian* *CEO**, PacketFlux Technologies, Inc.* >>>> Tel: 406-449-3345 | Address: 3577 Countryside Road, Helena, MT 59602 >>>> <https://maps.google.com/?q=3577+Countryside+Road,+Helena,+MT+%0D+59602&entry=gmail&source=g> >>>> forre...@imach.com | http://www.packetflux.com >>>> <http://www.linkedin.com/in/fwchristian> >>>> <http://facebook.com/packetflux> <http://twitter.com/@packetflux> >>>> >>>> >> >> >> -- >> *Forrest Christian* *CEO**, PacketFlux Technologies, Inc.* >> Tel: 406-449-3345 | Address: 3577 Countryside Road, Helena, MT 59602 >> <https://maps.google.com/?q=3577+Countryside+Road,+Helena,+MT+59602&entry=gmail&source=g> >> forre...@imach.com | http://www.packetflux.com >> <http://www.linkedin.com/in/fwchristian> >> <http://facebook.com/packetflux> <http://twitter.com/@packetflux> >> >> > -- *Forrest Christian* *CEO**, PacketFlux Technologies, Inc.* Tel: 406-449-3345 | Address: 3577 Countryside Road, Helena, MT 59602 forre...@imach.com | http://www.packetflux.com <http://www.linkedin.com/in/fwchristian> <http://facebook.com/packetflux> <http://twitter.com/@packetflux>
