I modified the pps_parport Linux Kernel Module to produce pulses in addition to receiving them. It's different from the existing pps_gen_parport in a few ways: *works with multiple parallel ports *timestamps assert or clear edge instead of just asserting at the top of the second without timestamping *pulse timing is adjustable *assert and clear data values are configurable
It is able to produce a pulse as narrow as 800ns with my hardware, a PCIe parallel card in a fast amd64 machine. The timestamps are accessed through the PPSAPI as normal. I still need to make some documentation, but all the load-time parameters are described in the driver source. I also added a few optional features to the standard input mode: * interrupt line polling to eliminate interrupt latency * local echo for measuring capture latency with an external counter * interrupt masking to allow operation with ports that have level-triggered interrupts I finally found some time to get the refclock_trimble driver in a usable state for testing the modified pps_parport driver. It's available at: https://gitlab.com/trv-n/ntpsec Usage instructions are located near the bottom of the docs/driver_trimble.txt file. Only the ntpd/refclock_trimble.c and docs/driver_trimble.txt files have been modified. I'm currently testing with an Acutime 2000. If anyone would like to try the driver out, there are several 2000s available on everyone's favorite auction site. Unfortunately the RS232-to-RS422 converter (37071-00) is expensive, and the cable connecting the two isn't readily available. I ended up having to make a converter and cable. I'll make some information available on the converter eventually, but it's pretty easy to build from the information in the receiver manual. The Trimble Thunderbolt does not have an event input, so it can't be used for testing the kernel driver. An EndRun Technologies Praecis Cf/Ct/II can be used to test, but a custom cable and possibly a level shifter will need to be built. I have a Cf that I'll be testing soon, along with a Palisade and Acutime Gold. Since it was easy to add support for the kernel driver into the trimble refclock driver, it may be worthwhile to add it to other drivers, but I'm pretty sure the only other non-trimble driver that has support for receivers with timemark-type inputs is the one that is being worked on by MLewis. I'll take a look at it and see if it is using the PPSAPI in a similar way -- it may be possible to use the modified parallel port kernel module on PC hardware with that refclock driver as well as the GPIO-type kernel driver he's working on. _______________________________________________ devel mailing list devel@ntpsec.org http://lists.ntpsec.org/mailman/listinfo/devel
