I have been able to record the output from the laptop but the Cetrek says DATA error. I am using the same serial port for reading from the GPS and sending to the autopilot.

Is it possible for you to send me the data that you managed to capture on a laptop that was output from Seatalk. Did you use a second laptop, and what did you use to 'see' the data?

The APB sentence should look something like:-
$GPAPB,A,A,0.10,R,N,V,V,011,M,005,011,M,011,M*82
although the last *82 doesn't seem to be needed (its a checksum). My bit of Visual Basic doesn't output it and the Cetrek seems to be happy enough.

I also assume that the Cetrek display has 'NAV DATA' displayed. This may be because the data is being sent with GPAPB,V,V,... which is an error indicator. As the manual shows on page 22 'NAV DATA', 'NAV READ' and 'NAV OVFL' are the three possible error conditions.
The fact that you get something would indicate that the pin connections are OK. That really only leaves baud rate but I would expect 'NAV READ' or 'NAV OVFL' for that. If you can 'capture' some Seatralk output I could use it to 'drive' my Visual Basic program which I know does communicate OK.

Ian

The output from the Garmin GPS to the AP is here.

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The output from the Laptop running Seatrak.

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I used another laptop and the hyperterminal to record the data.

Yes, the Cetrek shows NAV DATA. Baud rate is 4800.
In the software, Seatrak, I have been in contact with the software developers and they have tried in vain to modify the software to drive the Cetrek and I must congratulation them in their tireless work it trying to help us get this sorted. I will have time this incoming week to get this going again. In the software you can change from APa to APB, and turn on and off the strings that are outputted as well as checksums but I haven't got a combo that has worked.

Hi Mark,

Only observation is that the output is not showing either the APA or APB sentence. However the Cetrek documentation does say that a mixture of other sentences will do, provided they can give cross track error (e.g. XTE sentence), heading to waypoint (e.g. BOD sentence) and waypoint number (BOD sentence) and you have this output. Note that the Cetrek manual doesn't list RMB and RMC which provide the information as well.

I also note that each sentence has the * checksum. None of the outputs from my Thurya sat phone or the Magellan have any checksum and the Cetrek is happy with the output. Specifically I've only seen checksum mentioned for the RMB and RMC sentences. Could it be that the XTE and BOD shouldn't have the checksum?

I will modify my Visual basic software to take your collected data and see if I can fire it into my 727. Will not have access to the 727 until the weekend.

Regards,
Ian

That is very interesting, in the software I can change the output so will try that without checksum and only APA or APB.

Closer examination of the RMB sentence in your collected data may reveal a problem.

e.g. from your collected data
$GPRMB,A,0.09,L,002,003,5426.56,N,00538.04,W,000.6,199.8,,V*01
but I have come across this interesting snippet on a web page...

===============================================
RMB - The recommended minimum navigation sentence is sent whenever a route or a goto is active.
On some systems it is sent all of the time with null data.
The Arrival alarm flag is similar to the arrival alarm inside the unit and can be decoded to
drive an external alarm.
Note the use of leading zeros in this message to preserve the character spacing.
This is done, I believe, because some autopilots may depend on exact character spacing.

e.g. $GPRMB,A,0.66,L,003,004,4917.24,N,12309.57,W,001.3,052.5,000.5,V*20

==============================================

i.e. your double comma at the end could possibly be ,000.0, instead.

Something else for me to try on the testbed...

I have the laptop home with me to test stuff. Is there a virtual GPS program that can output NMEA data for the laptop?

Looking at the autopilot manual, it does not use the RMB information - see page 27. Could this still effect the autopilot?

One thing I don't think I have mentioned is that I can get the Garmin 128 to control the autopilot no problem but I don't have the option of using the laptop with chartplotter then and no routes available.

I hooked up my laptop to the 727 at the weekend.
Using my test software I was able to control the autopilot using simulated APB sentences.
I then tried simulating just the XTE and BOD sentences and this worked as well.
I then took your 'captured' data and fed that to the 727 and that worked also....
Did you check the wiring between the Garmin/laptop/727? If you wish I can send you my test software and you can try what I did. Sounds as though you have a cable problem, especially if you can connect the Garmin to the 727 and it works.
Ian

Yes, if you can send me the test software that would be great. Did you try using both nmea txt files? One of them is a Garmin 128 output which I found to work and the other is the laptop output which I couldn't get to work.

for the wiring of the serial port, I am using pins 2,3 and 5 for ground.

I will check with a multimeter the continuity of the wiring this evening but if I loop through pins 2 and 3 with a bit of wire in the serial socket, I can get the GPS to talk to autopilot and control it. I will also test your program to see if AP will listen.



Is it OK to make your NMEA program available for others?

The wiring looks OK except that I'm sure I have Sig+ of NAV1 on the 727 connected to pin TXD(3) of the laptop and Sig- of NAV1 on the 727 connected to Pin SG(5) of the laptop.

The 727 connector SCR'N is the cable screen and I don't have that connected. Screen is normally only connected to the chassis of the equipment at one one of the cable. Note that the 727 doesn't transmit therefore Sig- equates with SG.

By the way, I only replayed your laptop output to the 727 and it was OK. I didn't try the Garmin output but suspect that will be OK as well since you said that you get control with it.

You are welcome to pass on the program to others. No warranty expresed or implied. I have updated it since I sent you the version to allow user selectable comm port.

Ian

Wow, Ian, this is really annoying now that you say the the laptop out nmea log worked!

What settings did you use on the NAV1, there is NMEA0183 A or B, I'm not sure which to use?

Feel free to upload the program as a zip file to one of the file hosting services mentioned in the sticky post on this forum.

Mark

Not to hijack this thread but my 55 has a "not working anymore" Cetrek autopilot. I am in desperate need to find a users manual and wiring diagram (bought the boat used, with no docs on the autopilot). Anybody has any leads to where I might find those?

Thanks, David

Hi david

Welcome to the POC. If you search through this thread, there is a link to a Cetrek 727 manual in multi-page TIFF format which can be printed out. I scanned this last week and am glad that it can be of use to you. This has all you should need to check your wiring etc.

David,

I have downloaded various other Cetrek manuals from the web archive of the old Cetrek.com website. If you autopilot isn't the 727 perhaps I can help. Perhaps you could elaborate on 'not working'? Doesn't power up, doesn't respond to NAV input, gives FLT (fault) displays, etc etc

Mark,

Did you try swapping that connection on the distribution board?
No idea what my NAV1 is set to... it worked so I didn't need to explore that avenue. Will check this weekend.

Ian