Once upon a time, Jason Rabel <[EMAIL PROTECTED]> said: >But does shmpps support the PPS signal on a RS232-USB conversion? I would >think that with delays in the conversion & USB bus your PPS signal would not >be useful even if it did work.
shmpps doesn't have to support anything special for USB, since Linux presents a USB to RS232 port as just another serial tty (ttyUSB* instead of ttyS*). I know there is some additional overhead in going through USB, but I don't think it is that big of a deal; the bus speed is 12 Mbps and I would expect the DCD change is a single packet. Is my clock as accurate as somebody else's? No, maybe not. However, I believe it is as accurate as I can make it, since I don't have an RS232 port to use (and also I'm using USB bus power to power my GPS and USB to RS232 adapter, which is very convenient and I couldn't do with straight RS232). However, if you are going to start analyzing the accuracy, you'll need to compare the overhead of USB vs. doing old-style ISA I/O to a UART on a modern PCI chipset (that's not considered a high priority these days; how much latency is added in the UART emulation and the ISA emulation?). -- Chris Adams <[EMAIL PROTECTED]> Systems and Network Administrator - HiWAAY Internet Services I don't speak for anybody but myself - that's enough trouble. _______________________________________________ questions mailing list [email protected] https://lists.ntp.org/mailman/listinfo/questions
