How to output GPS signal to a DSC radio?

[sdowney717]

Made discovery.
If radio is turned on first. Then gps is powered on, the data appears every time within a few seconds. I verified this over 20 times and makes no difference which black wire in any combination is used. If gps is left on with data displayed in radio and radio turned off and on, no data appears ever. If gps turns on as radio turns on no data or as before only rarely.

Is that a symptom of the mismatch rs232 talking to rs422?

Also big black wire is cable shield.
Would getting the converter solve the turn on issue?

[sdowney717]

OK, found cheapest solution I can find. So cheap I bought 2 modules.
https://www.aliexpress.com/item/3280...chweb201603_52

video shows how it works.

https://www.youtube.com/watch?v=lFhPAb7JyM4

I seriously get now why when the USCG said 90% of DSC calls had no GPS info, was so true, as most people could not figure this out. There are people on my dock that can not figure out how to wire a simple battery charger, certainly not this either. I have helped many people wire up devices, but this is my first GPS like this.

[CarinaPDX]

That is just bizarre. The only thing I can think of is that if the GPS is sending data first the radio never synchs to the sentences, but that seems a stretch. It doesn't appear that the difference in standards would cause this - the GPS should just continue to transmit. I just don't know. It really is just speculation. Perhaps someone else has an idea of the cause.

Since we are not in the business of redesigning the hardware I suggest we move on. The simple thing to do is to have a power switch for the GPS and just remember to turn it on last. If you were turning the radio on with an external switch (or circuit breaker) you could connect the GPS to that as well, through a delayed-on relay. Something like this: https://www.ebay.com/itm/US-Stock-DC...t/312521025572 . If you look around you can find fixed-time-delay relays as well.

Greg

Edit: I see you posted while I was researching delayed-on relays. I prefer the packaged version to the open PCB but either should do the job. G

[sdowney717]

Originally Posted by CarinaPDX

That is just bizarre. The only thing I can think of is that if the GPS is sending data first the radio never synchs to the sentences, but that seems a stretch. It doesn't appear that the difference in standards would cause this - the GPS should just continue to transmit. I just don't know. It really is just speculation. Perhaps someone else has an idea of the cause.

Since we are not in the business of redesigning the hardware I suggest we move on. The simple thing to do is to have a power switch for the GPS and just remember to turn it on last. If you were turning the radio on with an external switch (or circuit breaker) you could connect the GPS to that as well, through a delayed-on relay. Something like this: https://www.ebay.com/itm/US-Stock-DC...t/312521025572 . If you look around you can find fixed-time-delay relays as well.

Greg

Edit: I see you posted while I was researching delayed-on relays. I prefer the packaged version to the open PCB but either should do the job. G

I figure the radio is just not ready for GPS data immediately at turn on, so with the GPS sending data as its booting it jams up inside the radio firmware, causes something to just stop, might be a firmware bug. And I cant tell if the GPS quits sending, really no way to tell that without hooking to a PC serial port. I think the GPS is not affected, its the radio.

The delay relay is an elegant solution. I also opened radio up and found the blue wire is powered on when the radio switch is turned on, so I sent a wire out the back to turn on the gps when radio is turned on by its on switch. Then I thought to check by powering the GPS on its own wire separate from radio, but t made no difference.

Radio just happened to have a sealed with silicone hole and a threaded unused ground port on the heat sink to put a black wire. Wire fit thru that and its still tight. My added wire is the red one with a knot. Gets +12vdc when radio is turned on.

[CarinaPDX]

Yes, as I have thought about it, it is almost certainly the radio at issue. The GPS is going to output its sentences once a second, no matter what. There is no feedback from the radio to shut it off. It could be that the data is overflowing the input buffer before the radio starts to process it, causing an error, which results in the radio ignoring it so that it can do its primary job of communications. Cobra makes good radios but their experience with data handling is pretty light. It seems they got their GPS module working, then left off all specs for the radio and GPS so they wouldn't have to support other GPS receivers. As long as it works to your satisfaction then no problem other than the extra install effort. Given how low the prices have dropped for marine VHF radios I think it makes sense to stick with the big boys like Icom and Standard Horizon (Yaesu) who have great experience with all aspects of marine communication. YMMV

Greg

[Moo]

As I mentioned way up the thread these budget radios often have very crappy interfaces.

Other that what you have already discussed the issue could be with a power supply sag as the radio is turned on causing some corruption in the GPS.

[sdowney717]

Originally Posted by Moo

As I mentioned way up the thread these budget radios often have very crappy interfaces.

Other that what you have already discussed the issue could be with a power supply sag as the radio is turned on causing some corruption in the GPS.

Yes I checked that by coonecting direct to battery and was no better

[sdowney717]

Originally Posted by CarinaPDX

Yes, as I have thought about it, it is almost certainly the radio at issue. The GPS is going to output its sentences once a second, no matter what. There is no feedback from the radio to shut it off. It could be that the data is overflowing the input buffer before the radio starts to process it, causing an error, which results in the radio ignoring it so that it can do its primary job of communications. Cobra makes good radios but their experience with data handling is pretty light. It seems they got their GPS module working, then left off all specs for the radio and GPS so they wouldn't have to support other GPS receivers. As long as it works to your satisfaction then no problem other than the extra install effort. Given how low the prices have dropped for marine VHF radios I think it makes sense to stick with the big boys like Icom and Standard Horizon (Yaesu) who have great experience with all aspects of marine communication. YMMV

Greg

I paid $83 at Amazon for it. New. They had 26 for sale at that price and all sold.

[CarinaPDX]

These GPS receivers are incredibly robust, so that is not likely to be the source of the problem (but without a scope on the output nothing is certain). And just because it is working now doesn't mean that we don't have to take care of proper grounding, for the day when there is a noisy environment.

I think the OP should send an email to Cobra about the problem. Maybe they will research it and release a firmware upgrade, or perhaps an upgrade is already available. If they don't know about the problem (unlikely) they might want to fix it, as they will probably be re-using the code in future products. At the least we might learn how serious they are about the marine market, Also, it would be interesting to know if there is a means of field-upgrading the firmware.

Greg

[CarinaPDX]

Originally Posted by sdowney717

I paid $83 at Amazon for it. New. They had 26 for sale at that price and all sold.

For that kind of savings a little imperfection can be tolerated.

Greg

[sdowney717]

Originally Posted by CarinaPDX

These GPS receivers are incredibly robust, so that is not likely to be the source of the problem (but without a scope on the output nothing is certain). And just because it is working now doesn't mean that we don't have to take care of proper grounding, for the day when there is a noisy environment.

I think the OP should send an email to Cobra about the problem. Maybe they will research it and release a firmware upgrade, or perhaps an upgrade is already available. If they don't know about the problem (unlikely) they might want to fix it, as they will probably be re-using the code in future products. At the least we might learn how serious they are about the marine market, Also, it would be interesting to know if there is a means of field-upgrading the firmware.

Greg

They won't know much IMO. They have their own gps which they make sure works with their radios. They would say we don't support others. I think they would say that. If I feel inspired I might mention it.

[CarinaPDX]

Originally Posted by sdowney717

They won't know much IMO. They have their own gps which they make sure works with their radios. They would say we don't support others. I think they would say that. If I feel inspired I might mention it.

You are being way too kind. Radios often share GPS data with other devices; NMEA talkers can usually feed up to 4 listeners. Dedicated GPS receivers are the exception on cruising boats, not the norm (admittedly small craft might not have another GPS source, although that would be unusual these days), And they failed to provide specs for either the GPS input to the radio or the output from the GPS receiver - basically bush league performance. Because it is a marine radio of recent manufacture it is reasonable to assume that it has an NMEA 0183, v.2+, interface, which implies RS-422 4800 baud, but they damn well should have documented that. Also, they don't spec which NMEA sentence(s) the radio can decode; fortunately most GPS receivers just dump out all of the common ones.

Greg

[sdowney717]

Originally Posted by CarinaPDX

You are being way too kind. Radios often share GPS data with other devices; NMEA talkers can usually feed up to 4 listeners. Dedicated GPS receivers are the exception on cruising boats, not the norm (admittedly small craft might not have another GPS source, although that would be unusual these days), And they failed to provide specs for either the GPS input to the radio or the output from the GPS receiver - basically bush league performance. Because it is a marine radio of recent manufacture it is reasonable to assume that it has an NMEA 0183, v.2+, interface, which implies RS-422 4800 baud, but they damn well should have documented that. Also, they don't spec which NMEA sentence(s) the radio can decode; fortunately most GPS receivers just dump out all of the common ones.

Greg

What device would be used to share this GPS data to many devices?
And we really dont know if the rs422 converter might have fixed the issue?

[Moo]

Originally Posted by sdowney717

What device would be used to share this GPS data to many devices?
And we really dont know if the rs422 converter might have fixed the issue?

An NMEA0183 talker can feed four listeners. You don't need another device.

[sdowney717]

Originally Posted by Moo

An NMEA0183 talker can feed four listeners. You don't need another device.

You mean just splice them all together?
Do these other NMEA devices require rs232, rs422 or can they use either ?
How about take a rs232 GPS, convert the signal to rs422, then connect it to 4 other listeners?