[Bug 224173] serial driver from 10.4 onwards doesn't correctly work in ntpd/DCF77 "parse" clock mode

Fri Dec 8 11:20:32 UTC 2017

https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=224173

            Bug ID: 224173
           Summary: serial driver from 10.4 onwards doesn't correctly work
                    in ntpd/DCF77 "parse" clock mode
           Product: Base System
           Version: 11.1-STABLE
          Hardware: amd64
                OS: Any
            Status: New
          Severity: Affects Some People
          Priority: ---
         Component: kern
          Assignee: freebsd-bugs at FreeBSD.org
          Reporter: freebsd-d9e at fasterix.frmug.org

I'm running a DCF77 (German radio time code) receiver in "raw pulse" mode in
ntpd.

The receiver emits 100 ms ("0") or 200 ms ("1") pulses on the RX and/or CTS/DCD
line of the serial port.

There are 59 pulses per minute, one per second except on second 59. See
https://en.wikipedia.org/wiki/DCF77

On FreeBSD 11.1 with ntpd, there are 2 modes in which the receiver can be used:
- "parse" mode, where the timecode is decoded bit by bit. In this mode the
serial port is configured at 50 bauds. A 100 ms pulse yields a character, a 200
ms pulse yields a framing error.
- "PPS" mode, where the uart driver timestamps a transition on DCD.

PPS mode works flawlessly.

On the other hand, the parse timecode mode (50 bauds) doesn't. Bits are lost (I
haven't yet investigated whether only 1-bits or 0-bits are lost, or if the
pattern is more complex).

On FreeBSD 10.4 this doesn't work either (same serial driver as in 11.1).

On the other hand, on FreeBSD 9.3 the receiver works (older serial driver).

Where this gets very interesting is that the above mentioned FreeBSD 9.3 runs
as a guest in a VirtualBox on the very same FreeBSD 11.1 host, with the host
serial port configured in VirtualBox to point to /dev/cuau0, and seen as a
16550 UART by FreeBSD 9.3.

It doesn't work on a FreeBSD 11.1 under VirtualBox, which is less surprising.

Relevant bits of my ntp.conf for the non-working timecode mode:

# Configuration for "timecode mode"
# DCF77 module on /dev/refclock-1 (link to /dev/cuau0)
server 127.127.8.1 mode 5
fudge 127.127.8.1 time1 1.843

Excerpt from failed parsing logs.

Dec  7 22:10:31 freebsd11-1 ntpd[701]: parse: convert_rawdcf: INCOMPLETE DATA -
time code only has 8 bits
Dec  7 22:10:41 freebsd11-1 ntpd[701]: parse: convert_rawdcf: INCOMPLETE DATA -
time code only has 4 bits
Dec  7 22:10:49 freebsd11-1 ntpd[701]: parse: convert_rawdcf: INCOMPLETE DATA -
time code only has 8 bits
Dec  7 22:10:59 freebsd11-1 last message repeated 2 times
Dec  7 22:11:01 freebsd11-1 ntpd[701]: parse: convert_rawdcf: INCOMPLETE DATA -
time code only has 1 bits
Dec  7 22:11:08 freebsd11-1 ntpd[701]: parse: convert_rawdcf: INCOMPLETE DATA -
time code only has 1 bits
Dec  7 22:11:10 freebsd11-1 ntpd[701]: parse: convert_rawdcf: INCOMPLETE DATA -
time code only has 8 bits
Dec  7 22:11:32 freebsd11-1 ntpd[701]: parse: convert_rawdcf: INCOMPLETE DATA -
time code only has 16 bits
Dec  7 22:11:34 freebsd11-1 ntpd[701]: parse: convert_rawdcf: INCOMPLETE DATA -
time code only has 8 bits
Dec  7 22:11:51 freebsd11-1 ntpd[701]: parse: convert_rawdcf: INCOMPLETE DATA -
time code only has 11 bits
Dec  7 22:11:53 freebsd11-1 ntpd[701]: parse: convert_rawdcf: INCOMPLETE DATA -
time code only has 8 bits
Dec  7 22:12:00 freebsd11-1 ntpd[701]: parse: convert_rawdcf: INCOMPLETE DATA -
time code only has 5 bits
Dec  7 22:12:17 freebsd11-1 ntpd[701]: parse: convert_rawdcf: INCOMPLETE DATA -
time code only has 12 bits
Dec  7 22:12:19 freebsd11-1 ntpd[701]: parse: convert_rawdcf: INCOMPLETE DATA -
time code only has 8 bits
Dec  7 22:12:40 freebsd11-1 ntpd[701]: parse: convert_rawdcf: INCOMPLETE DATA -
time code only has 15 bits
Dec  7 22:12:42 freebsd11-1 ntpd[701]: parse: convert_rawdcf: INCOMPLETE DATA -
time code only has 8 bits
Dec  7 22:12:51 freebsd11-1 ntpd[701]: parse: convert_rawdcf: INCOMPLETE DATA -
time code only has 3 bits
Dec  7 22:12:53 freebsd11-1 ntpd[701]: parse: convert_rawdcf: INCOMPLETE DATA -
time code only has 8 bits
Dec  7 22:13:07 freebsd11-1 ntpd[701]: parse: convert_rawdcf: INCOMPLETE DATA -
time code only has 7 bits
Dec  7 22:13:09 freebsd11-1 ntpd[701]: parse: convert_rawdcf: INCOMPLETE DATA -
time code only has 8 bits
Dec  7 22:13:20 freebsd11-1 ntpd[701]: parse: convert_rawdcf: INCOMPLETE DATA -
time code only has 5 bits
Dec  7 22:13:22 freebsd11-1 ntpd[701]: parse: convert_rawdcf: INCOMPLETE DATA -
time code only has 8 bits
Dec  7 22:13:29 freebsd11-1 ntpd[701]: parse: convert_rawdcf: INCOMPLETE DATA -
time code only has 1 bits
Dec  7 22:13:31 freebsd11-1 ntpd[701]: parse: convert_rawdcf: INCOMPLETE DATA -
time code only has 8 bits
Dec  7 22:13:39 freebsd11-1 ntpd[701]: parse: convert_rawdcf: INCOMPLETE DATA -
time code only has 2 bits
Dec  7 22:13:41 freebsd11-1 ntpd[701]: parse: convert_rawdcf: INCOMPLETE DATA -
time code only has 8 bits
Dec  7 22:13:49 freebsd11-1 ntpd[701]: parse: convert_rawdcf: INCOMPLETE DATA -
time code only has 2 bits
Dec  7 22:13:51 freebsd11-1 ntpd[701]: parse: convert_rawdcf: INCOMPLETE DATA -
time code only has 8 bits
Dec  7 22:14:00 freebsd11-1 ntpd[701]: parse: convert_rawdcf: INCOMPLETE DATA -
time code only has 2 bits
Dec  7 22:14:08 freebsd11-1 ntpd[701]: parse: convert_rawdcf: INCOMPLETE DATA -
time code only has 8 bits
Dec  7 22:14:10 freebsd11-1 ntpd[701]: parse: convert_rawdcf: INCOMPLETE DATA -
time code only has 8 bits
Dec  7 22:14:18 freebsd11-1 ntpd[701]: parse: convert_rawdcf: INCOMPLETE DATA -
time code only has 2 bits

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