On Tue, Mar 19, 2024 at 11:48:24PM -0700, Bill Unruh wrote: > > FWIW, I'm testing a daemon that reads an *i2c* gps device and > > feeds to chrony, and I need to bias it by about 0.250s -- I think > > it is just that slow to read the bytes from i2c. But I'm still > > looking for a foolish logic error like you suggest.
> That would surprize me very much, unless you are doing a very slow > polling of the gps pps. .125 sec sound like the original IBMPC I > bought in 1980. Maybe if you told us the hardware you are using and > the OS you are using someone could help more. Now if it is not PPS > but is rather reading the NMEA, then a slow baud rate could give you > that, since the sentences can be about that long at 600Bd. Also, you > really only need the NMEA for the first few seconds until the system > knows the seconds. I can't (easily) use the PPS line because it's a separate pin, not available over i2c. So yes, collecting NMEA lines. Hardware: Raspberry Pi 3B+ with this gadget: https://learn.adafruit.com/adafruit-mini-gps-pa1010d-module running legacy (32 bit) raspbian, and my hack here: https://gist.github.com/nobrowser/285d63410b9c2aec77a53587020cf2b6 I still want to try reading i2c with a super-slim C program instead, but I'm not too optimistic about it. -- Ian -- To unsubscribe email [email protected] with "unsubscribe" in the subject. For help email [email protected] with "help" in the subject. Trouble? Email [email protected].
