Implementing GPS on a VHF-DSC radio without GPS

[francois.lavoie]

I have just purchased a VHF-DSC radio without GPS:
Icom M330-11 VHF Radio Fixed Mount Black for $250 (taxes included). The owner manual is here:
https://productimageserver.com/liter...al/69884OM.pdf

In the manual, it is said to have a Common NMEA interface for external GPS/NAV connection (nmea 0183). In the owner manual we read:

NMEA IN/OUT LEADSGreen: Listener B (Data-L), GPS In (–)Yellow: Listener A (Data-H), GPS In (+)Connect to the NMEA output lines of a GPS receiver for position data.• NMEA 0183 (ver. 2.0 or later) sentence format RMC, GGA, GNS, or GLL and VTG compatible GPS receiver is required. Ask your dealer about suitable GPS receivers.• The GPS sentences input from this connector are given priority to over the sentences input from the GPS antenna connector.

I have searched for some diy GPS installations and found a few. Amongst which this one, which uses a u-blox NEO-6M GPS module that could be purchased between the price of less than $12 CAN.
https://www.electroschematics.com/neo-6m-gps-module/

This above thread explains how you can directly connect the NEO-6M GPS module to a computer, but also how you can get it to run with an arduino uno.

Two other similar threads on GPS alone or with arduino are here:
The first one is about the same:
https://lastminuteengineers.com/neo6...uino-tutorial/
The second one provides a GPS with wifi capabilities with a HC-12 transceiver board:
https://www.allaboutcircuits.com/pro...2-transmitter/

Interested enough, I have bought rapspbery pi 3 and an arduino R3 uno elego super kit. Its hard for a newcomer to understand where it will lead me, but in these COVID era there is a lot of time to spare.

My question are:
Will the u-blox NEO-6M GPS module alone directly plugged to my VHF-DSC radio will bring the necessary GPS data to VHF-DSC radio? Or will I need to interface it with an arduino uno?

Would a NEO-6M GPS module together with HC-12 transceiver board permit GPS feed to the nmea wiring to VHF-DSC radio, and in addition GPS data broadcasting to a Android tablet (I have a samsung Galaxy tab A model SM-T90) which would feed the navionics app or opencpn app?

Thanks for commenting. Hoping not to be too much naive.

[Kelkara]

I did exactly this to feed GPS data to my VHF.


For me, the short answer was no, it is not a direct connection. The GPS unit will output data at 9600 baud, but my radio would only read data at 4800 baud. So I had to use an arduino to read the 9600 data and echo at 4800 on another serial port. I don't know what the best practise is for NMEA0183 connections, but I also used a Max485 RS485 interface to connect it to the NMEA0183.


It's been working fine for about three years now.

[sail sfbay]

Do you have a separate GPS? If so, you can do it with a NEMA interface. A simpler option is to purchase a Standard Horizon GX 2400 Matrix with DSC, GPS and AIS receiver. I chose this route since I wanted to avoid extra connection to the VHF radio AND it allowed me to overlay AIS from the VHF radio on my chartplotter with a NEMA connection. I had my marine electronics guy do it since it was fast and easy for him.

[EarlWer]

What about the other direction? From OpenCPN to the VHF?
I bought a USB GPS from Amazon:
https://www.amazon.ca/USGlobalsat-BU...5662534&sr=8-1

Works fine with my RPi 4 and OpenCPN, but I have not done much more with it yet...
(for my new/old boat).

[markcouz]

I tried a u-blox GM8-4883 to try and feed GPS to Icom 412 and Icom 802 for DSC function - tried for days including downloading u-center to change default 9600 baud to 4800 baud.

I got the occasion momentary sign of life but 99.9% not usable. The same gps when connected to my nmea multiplexer worked flawlessly, allowing wifi input to Linux box running opencpn.

In the end I got an old Garmin GPS12 which worked with the Icom equipment when set to 4800 baud (only used for Icom equipment).

Note that the GPS12 will report the incorrect date because of 20year rollover issue, but time and position are accurate.

[francois.lavoie]

NEO-6M modules have a standard 9600 baud rate, which could be modified to other speeds including 4800. The information will be store on the chip and kept until the rechargeable battery of the NEO-6M module is empty of charge:
https://www.u-blox.com/sites/default...-HW-09005).pdf

NEO-6modules provide configuration pins for boot-time configuration. These become effective immediately after start-up. Once the module has started, the configuration settings can be modified with UBX configuration messages. The modified settings remain effective until power-down or reset. If these settings have been stored in battery-backup RAM, then the modified configuration will be retained, as long as the backup battery supply is not interrupted
https://www.codrey.com/arduino-proje...m-gps-modules/
The battery is automatically recharged when power is applied and keeps data intact for up to two weeks without power.

The only exception is the neo-m9n-module which is configurable which is permanently configurable:https://www.u-blox.com/en/product/neo-m9n-module

The other way around would be to install the older NEO-6M module on a arduino card:https://www.u-blox.com/en/product/neo-m9n-module

The configuration stocked on the arduino should make the 4800 bauds permanent. Tell me if I am wrong?

[francois.lavoie]

@EarlWer:


Did you have some peculiar difficulty implementing the Pi? And how did you connect the Pi and the VHF-DSC radio? Is it thru NMEA wiring?



Logically, the following assembly could be plugged in the Pi:
https://www.electroschematics.com/neo-6m-gps-module/





And then adjusted thru the Pi openplotter Sensors interface.

[j.g.evans]

Look for a GPS with a direct NMEA 183 output. Many GPS with a USB connection will have a serial to USB converter in the cable. You can cut off the cable and get to the wires. You will need 2 for the GPS 4800 bps NMEA 183 and one more for power, probably 5V. Look on eBay for older Garmin GPS and then go to their web site for information. For example the Garmin GPS 18 and GPS 16/17 HVS are OK with 12 V. There are many GPS pucks from China. You can mount the GPS below deck to keep it out of the weather.

[CarinaPDX]

There is nothing simple about GPS.

First, why a u-blox 6? That is pretty old technology. It will work for a GPS (only) position, just a little slower to acquire a fix and probably a tiny bit less accurate but otherwise fine. The current product is a neo 8, which has been around several years itself (the ublox 9 series is just coming out). The ublox 8 can use up to three GNSS networks, out of the four available (GPS, GLONASS, BeiDou, Galileo), and is also available cheap.

The modules from u-Blox need 5VDC to operate (plus an antenna if not included) and typically output NMEA-formatted data at logic levels (0V and 3.3V or 5V). For our uses we typically provide 12VDC and need RS-422 signals (-6V and +6V). So for a freestanding GPS receiver providing data to a VHF or chartplotter there needs to be a DC-DC power converter and a level shifter for the data stream. Most of the readily available GPS pucks have USB interfaces, which provide 5V and use logic levels so they don't have the extra circuits. It is not difficult to find the right receivers but unfortunately it is easy to find ones with misleading descriptions that don't fill the bill.

Confusingly there are several ways for the default configuration to be programmed by vendors. Whichever way is used the default can be overridden for the session by programming, using the data interface and a PC with u-Blox software (difficult) or with a Linux box and GPSd (much easier). Unfortunately any changes will be lost on restart unless the module was packaged with some flash storage for the purpose. Flash storage also enables firmware updates, which shouldn't be an issue at this point.

So, without going into the gory details, the module you want is a u-Blox NEO M8N, aka 8030. You will need the module with antenna, not just the module alone or the antenna alone (easy mistake to make). If the default configuration is not going to match your needs then it will need to include flash storage for storing the new configuration, and you will need the ability to connect to your computer via RS-422, and the software and skills to do it. (Look around on eBay or aliexpress and you will probably find your configuration). While you could get an inexpensive DC-DC power supply if the receiver is 5V it is easier to get one that includes that, and the level shifter for RS-422 data levels.

For those looking for a GPS puck get one with the same module and the flash storage for configuring.

Greg

[hzcruiser]

May I ask why you want GPS on the radio, Francois? Only so it can send out your position in an emergency via VHF, right? I'd say that's of limited use, depending on your sailing grounds.
On top of that, I would not really trust this to work reliably in an emergency, since the battery voltage might already be fluctuating and then you rely on the pi to work if that's used as an interface.
For sailing on the lakes VHF would be fine to hail for help and let them know where you are. For offshore VHF might not work the distance.
Hence I would rather buy an EPIRB for the latter.

[francois.lavoie]

@hzcruiser
I will sail on the fleuve Saint-Laurent east of Quebec city up to Tadoussac and Rimouski this summer. We will be in a flotilla. I was told by the leader that a VHF-DSC radio was appropriate.

[TBear60]

Hello Francois.
Help yourself to less complication. You can get the same radio with the onboard GPS. This will save you trying to do the electronic "gymnastics" to get the NMEA 0183 into the radio from another source. That solution is like making three lefts to make one right. Garmin is the only chartplotter company that still has a hardline NMEA 0183 hook up to their unit. Everyone else is NMEA 2000. And there are no NMEA 0183 to NMEA2000 "translators". It's two different languages completely. Essentially, with NMEA0183 you have to program the information receiver to whatever the transmitter is sending and it's not straightforward, trust me. Unless you're a programmer or electronic nerd (no offense) by choice, save yourself the headache. If you're like me, I'm a boater, I choose to boat as simply as possible. Also, if you choose to go forward with the NMEA0183 translators as other Posters have suggested, if you ever have an issue with the extra equipment, you'll have a bugger of a time trying to get it sorted. Simplicity is the rule of thumb in my opinion.
Return the non-GPS Icom 330 to the Retailer you bought if from and exchange it for the Icom 330G with the onboard GPS. You'll have the added benefit of a redundant backup GPS unit. You can even do waypoints on the GPS equipped VHF! And yes, the Standard Horizon GX2400 is a much better unit all the way around. Especially for the price. They're crazy for pricing the unit so low. But hey, we win! If you do go that route, you will have to install a NMEA 2000 starter kit, if you haven't already. Going with the GX2400 enables you to have the radio talk to your Chartplotter, so you get the best of both worlds; ie the onboard GPS plus the Chartplotter GPS, plus the AIS receiver!
Good Luck.

[francois.lavoie]

@CarinaPDX
What about this Radiolink M8N GPS Module:
https://www.robotshop.com/media/file...l2016.7.13.pdf
Price $35 CAN:
https://www.banggood.com/Radiolink-M...N&rmmds=search
I found no indication on settin the baud rate on this type of chip, neither setting it permanently with an arduino, I thought to use an arduino nano.

RS422 to TTLmax490 chip:
https://datasheets.maximintegrated.c...487-MAX491.pdf

Price $6 CAN
https://www.banggood.com/RS422-to-TT...N&rmmds=search
I thought that rs432 was sufficient as the GPS information has only to go one way. Already I had bought USB to TTL Serial Converter:
https://images-na.ssl-images-amazon....AC_SL1500_.jpg

I really need duplex to GPS?Thanks.

[markcouz]

This is a thread about how to interface NMEA0183 to a DSC radio, not whether or not a DSC radio is a good idea.

I am one of many who is interested in the answer - I already have a DSC VHF and DSC SSB, so really don't care about the opinion regarding its value.

There are plenty of threads where people are seeking that opinion...

[francois.lavoie]

@TBear60
In fact, I have been on linux forum since 2005 with a small slackware distribution called Porteus. In my 20s, I programmed with basic and pascal languages. This is quite far knowledge. But recently I got interested in python, which I do not master at all, but which is interesting me. With a raspbery pi and some arduino boards I have got really excited recently. I have time to spare on the verge of being retired. Do you understand that does not seem trouble for me?


Thanks.