Tim Shoppa wrote: > Hal Murray <[EMAIL PROTECTED]> wrote: > >>> PCI 3.3v board with: >>> 10Mhz OCXO (provision for external clock source?) >>> Uart (serial is an endangered on many PC's) >>> Free running counter driven from the OCXO and readable by PC >>> inputs to latch the counter (how many?) with the latched result >>> also readable (for PPS) >>> >> I've been daydreaming along the same line but haven't hit a combination of >> ideas that feels good enough to actually do anything. >> >> My list has a FPGA in the middle. The problem with that is that newer FPGAs >> don't work on 5V PCI which is what all of my PCs have. The only 3V slots >> I've seen are in high end (noisy, expensive) servers. The PCI slots on >> Soekris boards are 3V. That adds another option to think about. >> >> There are several possibilities for dealing with 5V PCI. >> [ BGA's, Gold Fingers, etc.] >> > > My gut feeling: back up a little bit. Figure out how to do what you > want without a PCI bus, without gold fingers, without BGA's, etc. > > I had several goals in mind when I asked the initial question:
1) a low cost high stability ntp stratum 1 clock board - something that when added to a sub $100 gps would yield a really stable time source for ntp. To do this it really needs to let the main cpu read the counters in a predictable, consistent time which is why I wanted PCI (3v because I have soekris boxes). 2) it would also be nic to be able to add a low cost frequency synth to the design. What I've seen so far there are designs out there based on various cpu cores and or f/c pga chips that are close to what I'm thinking. The replies from the list have been really helpful - I'm going to do some more research and look closely at the existing designs and see what I can adapt. What prompted this in the first place was the horrible temperature sensitivity my soekris boxes exhibit - I can only keep them to within 10us of the gps 95% of the time and the occasional 100us excursion is not uncommon. I want to be stable to the limit of the gps I'm using - for no other reason than the belief that I can do it for way less than commercial devices using open source software and low cost hardware. In other works I'm hacking for the sake of it :-) John _______________________________________________ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts