Help me interface these two nautical devices
I'm crew on a boat (wooden 8.5m from 1973) which has a GPS and a tiller pilot that seem to work fine separately, but don't seem to want to talk to one-another. My captain is adamant this combination "used to work, but is not working now"; I myself have never attempted to use the autopilot, nor seen it in use.
The GPS is a Garmin GPSMap 182C which talks NMEA 0183 v3.0; According to its documentation, it sends "GPRMC, GPGGA, GPGSA, GPGSV, GPGLL, GPBOD, GPRTE, and GPWPL (as well as PGRME, PGRMZ, and PSLIB)".
The pilot is a Tillerpilot TP32 which also talks NMEA 0183. According to its documentation, it accepts "APA, APB, RMA, RMB, RMC, BWR, BWC, VHW, XTE (as well as VWR and MWV)".
As you'll notice, these abbreviations are helpfully incomparable, and I haven't become wiser by studying references.
The wiring connections I have all quadruple-checked; the only thing I cannot check is the actual data content of the NMEA signal data. I have also triple-checked that the NMEA settings are sane (GPS Port 1 out: NMEA v3, 4800 baud; GPS Port 2 out: None; and yes it's port 1 that's connected through to the tiller pilot's socket). I have been unable to determine the baud rate of the Tillerpilot, and the parity settings of both devices, but I must assume they are set to a common standard.
So my questions are:
- Are these two devices, in fact, compatible?
- If they are, what more can I check?
If necessary please advice in comments for the following:
- Should I post this else instead, and if so - where?? (There seems to be no good fit for questions of an nautical-electrical nature. I posted to Meta, which suggested either Outdoors or Electrical; the latter just closed my 1st try as off topic so I'm also trying here.)
- Are there any better tags for this question here?
This post was sourced from https://outdoors.stackexchange.com/q/21979. It is licensed under CC BY-SA 4.0.
1 answer
Garmin GPSMap 182C and Simrad TP32 share the same language (NMEA 0183), but they do not have enough in common to talk about.
The NMEA sentences that the 182C can transmit are GPRMC, GPGGA, GPGSA, GPGSV, GPGLL, GPBOD, GPRTE, GPWPL, PGRME, PGRMZ, and PSLIB. The first two letters of these identifiers are the Talker ID. GP stands for GPS receiver. PG and PS belong to Garmin proprietary sentences. Let's remove the talker ID, and forget about proprietary sentences, then we are left with:
BOD, GGA, GLL, GSA, GSV, RMC, RTE, WPL
The TP32 understands
APA, APB, BWR, BWC, MWV, RMA, RMB, RMC, VHW, VWR, XTE
The only sentence they have in common is RMC (Recommended Minimum Navigation Information). Through this sentence, the TP32 can receive the time, the position, the speed (over ground), and the log (distance sailed, over ground).
The TP32 is an autopilot. It requires some input about where to go. Normally this information is provided as a bearing and/or cross track error:
- The bearing could be provided through one of the sentences
APA, APB, RMB, BWR, or BWC. - The cross track error could be provided through one of
APA, APB, RMB, or XTE.
The 182C on the other hand side is less flexible. It cannot transmit the cross track error. It can transmit only one sentence that contains the bearing, that is BOD (Bearing - Waypoint to Waypoint), but the TP32 does not listen to BOD. These two devices are compatible on protocol level, but connecting them is - unfortunately - useless.
This post was sourced from https://outdoors.stackexchange.com/a/22143. It is licensed under CC BY-SA 4.0.
0 comment threads
0 comment threads