DIY GPS HEQ5 cable opinions please

[Extreme Fencer]

Hi I have an old Garmin GPS unit the sort that displays the data only no maps but it will display.routes etc.

I have the 4 pin data cable to connect it to cigar lighter and rs232 to a computer.

As the pin out of thegps is Txd and Rxd and the data in on my HEQ5 mount RJ11 multi purpose port excepts the same data would the mount recognise the data input from my gps?

I assume the GPS mouse dongle you can get is only needed for initial set up then can be removed.

Thanks in advance

[IanL]

That's a bit like asking "I write with a pen and paper, and so do people in Spain, so will I understand what they write?" The answer is, "Yes, if you speak Spanish, otherwise no."

In the first instance you would have to connect the GPS device to the SynScan handset, not directly to the mount. (The handset port on the mount is TTL voltage, so if you connect and RS232 device directly to it you will fry the motor board in the mount. The other RJ11 port is an ST4 autoguider port which doesn't accept any sort of data, just voltages to guide).

You should be able to connect the RS232 from the Garmin to the SynScan handset with no problems, provided you have or can make an appropriate cable (pretty easy, just have to connect Txd on one end to Rxd on the other, and vice versa, plus connect ground). Then you'll have to see if the Garmin speaks an appropriate protocol by default or can be made to speak one in its settings (plus you may have to adjust the baud rate on the Garmin, I think the handset wants 4800 baud though it won't do any harm to try other speeds if that doesn't work.

After that you can try any different protocols that to the Garmin supports, RTFM on that one, and see if anything works. The manual for the SynScan GPS mouse is here, and might be worth a read to see if it gives you any useful pointers for the Garmin:

http://www.opticalvision.co.uk/documents/198.zip

[IanL]

Sorry should have also said the other option might be to take a look at EQMOD if you are using a laptop instead of the handset. If you can get the Garmin talking to the PC via RS232 (or make/buy and RS232 to USB cable) you may be able to install a driver from Garmin to talk to the GPS device and relay that info to EQMOD somehow; not investigated GPS devices yet myself so not sure how EQMOD talks to GPS devices on the PC, but it is another avenue to explore.

[chrisshillito]

You should be able to connect the RS232 from the Garmin to the SynScan handset with no problems, provided you have or can make an appropriate cable (pretty easy, just have to connect Txd on one end to Rxd on the other, and vice versa, plus connect ground). Then you'll have to see if the Garmin speaks an appropriate protocol by default or can be made to speak one in its settings (plus you may have to adjust the baud rate on the Garmin, I think the handset wants 4800 baud though it won't do any harm to try other speeds if that doesn't work.

Wouldn't get your hopes up on that one. When the synscan first supported GPS you could plug any GPS unit into it so long as it talked NMEA. However synta/skywatcher soon took steps to change their firmware prevent operation of third party devices - that's why they can get away with such an expensive GPS unit!

EQMOD just monitors a COM port for NMEA strings, so as long as that's what your GPS is sending out, any you can have them arrive at a windows COM port, then EQMOD should work fine.

Chris.

[IanL]

From what Chris says, depending on the age of your handset firmware you may have no choice but to shell out for a Skywatcher GPS mouse, or go down the EQMOD route if your Garmin can be set to output NMEA protocol.

If you decide on EQMOD, an RS232 to USB converter cable would be needed. Here are some I have seen mentioned before, but haven't tried. Doubtless plenty of others on the market:

http://www.ftdichip.com/Products/Cables/USBRS232.htm

Of course then you'd need a laptop, an EQDIR adapter (http://eq-mod.sourceforge.net/vendors.html), or use the handset in PC direct mode (but see the caveats on the EQMOD site before doing that).

[Extreme Fencer]

Thanks for the replies I have had the garmin talking to my ancient laptop and used msautoroute with it. The laptop is so slow it can't handle stelarium so I can't use that to control the mount. I was just playing around with some cables I need an RJ11 with all the wires attached. All the old phone cables and modem cables I ve got don't have enough pins wired.

Was just an experiment as got the day off due to the snow.

[chrisshillito]

The laptop is so slow it can't handle stelarium so I can't use that to control the mount.

I bet CDC would work if ever you wanted to go down that route.

Chris.

[Extreme Fencer]

The laptop is a 700mhz pentium running W2000. It can barely run Firefox let alone anything more processor hungry. Could be the graphics are to old for it aswell Only fished it out of the computer bits box to update my synscan handset as it had a serial port

[P_Monty]

Digging up an old thread here, but I've got a similar idea. I fancy using an old hand-held garmin to give my synscan goto controller an accurate time and position feed.

If I've understood what's been said already:

It'll plug into the RJ11 on the handset, not the one on the motor control board;

It probably won't work because the firmware doesn't understand nmea anymore...

So, I was thinking - is the correct data format used by the skywatcher mouse known? I'm thinking that if it is, this could be a fun little project to convert between the two with a raspberry PI or similar (though it would also need to make sure the garmin and the Pi can communicate through my 232-USB converter) - it may need some form of digital IO on the Pi (I'm sure I've seen suitable daughter boards available)..

So am I talking total rubbish, or is it possible? - Don't need to know how - just whether it can be done.

Thanks

Paul

[astroalex]

Paul, did you get anywhere with this idea? I have just tried couple gpsfeed++ simulator to Synscan, as expected -- no luck.