Help with first foray into NMEA required please.

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fredrussell

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I picked up a cheap Standard Horizon CP155c chartplotter at a boat jumble recently. It didn't come with an antenna or the cable, and to buy these would not really be worthwhile on an old piece of kit such as this so I'm hoping to connect it by NMEA to a Ublox GPS receiver (via 12v to 5v converter).

The Ublox receiver is powered up and green LED is flashing. Could anyone offer some advice as to which wire(s) from chartplotter wiring harness to attach to TX and/or RX on the Ublox please.

Here's a pic of wire functions from the manual:

 
Plotter's blue wire to the uBlox's NMEA output. Plotter's green wire to whatever the uBlox uses for NMEA ground, which is probably its negative power connection. There's no need to connect anything going the other way.

Pete
 
Thanks Pete, the Ublox has four connections:

VCC
TX
RX
GND

I'm fairly sure VCC and GND are for +ve and -ve respectively from the 12v to 5v converter. LED on Ublox is flashing away wired as such anyway.

TX and RX are, I think, Transmit and Receive.
 
Yep, I came across that online, couldn't work out why they're different. The manual I have is the one that came with the chart plotter.
 
Just tried with blue to TX and green to GND but nothing doing. I might try yellow to TX as per online manual and see what happens.
 
fredrussell said:
Just tried with blue to TX and green to GND but nothing doing.
Click to expand...

You should probably go into the plotter's menus and ensure that Input 1 is enabled, set to NMEA0183 rather than any weird proprietary formats, and set to the appropriate speed (aka baud rate).

Come to think of it, what speed does the uBlox default to? Being modern and not especially intended for old boaty stuff, it's probably quite high (19200?). The docs will say. If the plotter can match the GPS's default speed then set that, otherwise you'll need to change the setting in the GPS. I believe there's a windows tool for that, but you'll probably need a USB - 5v serial adaptor to connect it :(

Pete
 
Well, my first foray into NMEA has, thus far, not been a successful one...

I've now tried with the blue wire from plotter connected to TX on Ublox: no joy. Then with the yellow wire from plotter to TX on Ublox: no joy.
In both cases, green wire from plotter to GND on Ublox, 5v +ve to VCC on Ublox, 5v -ve to GND on Ublox.

Ublox green LED is flashing - I'm assuming this means its functioning and outputting data.
Ublox default settings are 9600 Baud, 8 bits, no parity bit, 1 stop bit

I've set the plotter parameters to match the Ublox default settings.

Am I right in saying that the Ublox will start outputting data sentences the moment its switched on? The plotter has a setting where it displays incoming sentences to ports 1,2 or 3 and as yet no data is shown during this test, either in hex or ASCII.

I'm stumped!
 
fredrussell said:
Well, my first foray into NMEA has, thus far, not been a successful one...

I've now tried with the blue wire from plotter connected to TX on Ublox: no joy. Then with the yellow wire from plotter to TX on Ublox: no joy.
In both cases, green wire from plotter to GND on Ublox, 5v +ve to VCC on Ublox, 5v -ve to GND on Ublox.

Ublox green LED is flashing - I'm assuming this means its functioning and outputting data.
Ublox default settings are 9600 Baud, 8 bits, no parity bit, 1 stop bit

I've set the plotter parameters to match the Ublox default settings.

Am I right in saying that the Ublox will start outputting data sentences the moment its switched on? The plotter has a setting where it displays incoming sentences to ports 1,2 or 3 and as yet no data is shown during this test, either in hex or ASCII.

I'm stumped!
Click to expand...

Can you set the chartplotter to an NMEA receive speed of 9600?

They sound like the kind of variable parameters I used to have to set with serial modems and telnet in the old days whereas with NMEA I've only ever seen fixed 4800 / 8 bits / no parity / one stop bit or the high speed for AIS.

It's probably just that my NMEA receivers are less flexible that your SH.

Richard
 
I have an old VDO 10inch colour chartplotter. It originally worked on my boat using its own GPS antenna, which was 5 volt. When that failed I connected an Evermore 320 bare wire GPS and worked it with that. I have now removed it from the boat, but the Evermore remains on board to supply GPS position to the VHF. As the plotter has a 5 volt output I connected a Ublox USB dongle. It starts flashing green soon after connection, but I have tried just about every possible combination of connections with no result. I suspect that the old plotter uses an earlier version of NMEA 0183 It will accept a lot of input strings, according to its manual including Gll and GGA, however if you look at the Actisense NMEA 0183 Information Sheet there is a paragraph on page 7 which might explain why it does not work, if the sentence format has changed between the NMEA version in the plotter and the newer version in the dongle. Download the information sheet here http://www.actisense.com/products/nmea-0183/nbf-3/downloads-nbf-3.html by clicking on the Tech Talk Documents download link.
 
Thanks Norman for that. Had a good read of it.

According to the manual of the chartplotter "the GPS products interface protocol design is based on...NMEA ASCII interface specification. These standards are defined in "NMEA 0183 Version 2.0".

Can I assume from that that my chartplotter is not listening for 'early' NMEA from a 'late' NMEA talker?

RichardS said:
Can you set the chartplotter to an NMEA receive speed of 9600?

Richard
Click to expand...

I can indeed - but as yet to no effect.
 
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Normally when I and facing a situation like this . I firstly use one of these to ensure that some kind of RS232 signal is being sent out.
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Once I know I have an output and on which wire, I connect the device to a PC with either a RS232 port or RS232 to USB converter and using some terminal emulator of NavMonPC to see the outout changing the baud rate if I get garbage.

Once I know this I then connect to the target device again with a RS232 monitor to ensure a signal is being sent.
 
fredrussell said:
Am I right in saying that the Ublox will start outputting data sentences the moment its switched on?
Click to expand...

Yes, it should. I have one talking to an Arduino to make a standalone speedometer, and it just starts squirting out NMEA sentences as soon as it has a fix. The green flashing light is the pulse-per-second timing signal and that only runs when there is a fix.

Maybe it is that NMEA sentence version thing? I would connect it to a serial terminal on a computer to see exactly what's coming out.

Pete
 
Hmm, trouble is I don't have a computer with a serial terminal - macbook user. I think at this point I may admit defeat and keep my eyes peeled for a Standard Horizon GPS antenna and use that. I'm not the most gifted with electronics to be honest and I'll soon be slipping out of my depth if I start getting involved with sentence versions and the like. I think Norman's hunch may be closest to the truth - that this is an old machine (2005 I think) trying to talk to a very modern GPS receiver.
 
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fredrussell said:
Hmm, trouble is I don't have a computer with a serial terminal - macbook user.
Click to expand...

iMac here, at least for home stuff like this :)

You can get USB adaptors for either full-voltage RS232, or the 0-5v TTL version, and this software is very good for talking to them especially if you're not an expert at the fiddly bits: https://www.decisivetactics.com/products/serial/ . The 7-day free trial would get you past this hurdle.

Pete
 
Cheers Pete, but I'm really not confident with electronics and diagnostics. I'm not in a huge hurry to have a chartplotter on the boat, (I have an iphone with Navionics) and if I'm patient I'm sure I can find a proper SH antenna on UK or USA ebay.
 
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