Implementing GPS on a VHF-DSC radio without GPS

[francois.lavoie]

@CarinaPDX
I am no expert, but fell on this video comparing the neo-6m and the 8m modules. The conclusion is that the horizontal precision of both modules are equal. The precision would more depend on the position of the satellites:

https://www.youtube.com/watch?v=FmdG66kTfsI

Also he states that both could be adjusted with the u-center sofware:
https://www.u-blox.com/en/product/u-center
Which should mean adjusting the baud rate for both.
The 8m contrarily to the neo-6m is not compatible with the tinygps libraries used with arduino modules. Arduino modules which I thought to use to keep these two modules at the necessary 4800 baud rates compatible with nmea0183. In fact, from what I understand an arduino(hardcoded)-gps module should add speed when connected to the raspbery pi, compared to a gps only module to the pi.
Sorry, if I get all these information wrong. I have read but did not play much yet with all these hardware components.
Thanks.

[Kelkara]

Of the people replying to this thread, it seems like I may be the only one who has actually done what Francois is proposing.

This is what I made ... I'm no expert, so it could maybe be done better ... but it has been working for a few years now.

The arduino sketch simply reads the GPS sentences coming in the "software serial" port at 9600, then echos it out the regular serial port at 4800. You can also read the output on the USB port to check that the correct data is getting through ... If you're going to go this route, you ought to have no trouble writing your own arduino sketch ... My code is a bit messy since it was one of my first arduino projects, and I wanted to calculate SOG COG etc, so it's not really worth sharing.

By the time it's all finished, it's barely cheaper than spending $50 on a manufactured NMEA0183 GPS receiver ... but it was a fun project.

[francois.lavoie]

Changing the baud rate of the gps module:
https://freematics.com/forum/viewtopic.php?t=1759
Ok. I got it for the use RS422 to TTLmax490. I you want to adjust the baud rate, you need full duplex capibility. A $6 such device.
https://www.banggood.com/FT232-USB-U...N&rmmds=search

Thanks.

[francois.lavoie]

@kelkara:
That is it. So you are directly connected to the VHF-DSC radio. What is your GPS chip? And did you put your GPS-ARDUINO module into a water proof box?

[CarinaPDX]

Originally Posted by francois.lavoie

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 wouldn't go that way. These GPS receivers intended for drones use TTL for output of GPS data, and a separate I2C interface for the gyro/compass output. It is a 5V unit, and without flash. Just a PITA for our usage.

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.

The uBlox 8 modules can be configured as long as the interface is bi-directional; most often users just listen to the output and may not even implement the other direction, but it is there. But without flash it would have to be re-configured on every power-up (unless the default was acceptable): give it a pass.

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

Price $6 CAN
https://www.banggood.com/RS422-to-TT...N&rmmds=search

Yes, this should work to connect a TTL-level output to a VHF NMEA 0183 input - but why not buy a GPS with the proper output?

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.

This converter is bidirectional so you can use it to configure a GPS. Of course this is pointless unless there is a flash chip; as soon as you shut it down it will lose it before you can connect to the VHF. And as I said above, you only need it if you want to change the configuration.

Something you should know before buying: uBox 6 is GPS (only), uBlox 7 is GPS and GLONASS, early uBlox 8 is GPS, GLONASS, and BeiDou, and recent uBlox 8 is (roughly) 3 of the 4 possible GNSSes (GPS, GLONASS, BeiDou, Galileo). Depending on what the assembler chose the uBlox 7 may or may not receive GLONASS by default, and the uBlox 8 may be just GPS and GLONASS by default - or some other selection. Vendors will indicate which are supported by default. So the best approach is to pick a unit with the defaults you want instead of configuring it yourself.

Here is a unit that should work out of the box (uBlox M8N, 4800 baud, 12VDC, 232 output levels, flash memory):

https://www.aliexpress.com/item/4000953114064.html

If you wanted to activate BeiDou or Galileo then you would need a RS-422/485 to USB adapter for use with your computer. If you don't want to configure yourself then you could buy this one (which apparently does not have flash but worth asking):

https://www.aliexpress.com/item/4000917911171.html

or a uBlox 7 with flash but limited choice of GNSS:

https://www.aliexpress.com/item/32967240351.html

I have looked at these but please check the specs before ordering - my eyes are blurring at this point. Also, note that these vendors will change the defaults for you if you ask in advance, so if you order 4800, RS-232 level, and GPS, GLONASS, and Galileo as the default you may not need to configure.

BTW RS-232 levels are +/- 3V-15V, while RS-422 levels are +/- 6V. The ICs used for the purpose are usually interoperable but not guaranteed.

Of course if you really want to buy a 5V TTL receiver then have fun with the 5V power supply, TTL to RS-422, and Arduino (just looking for an excuse?).

Greg

[francois.lavoie]

@Greg:
Its very nice to you to have taken all the time to answer my numerous interrogations.

[CarinaPDX]

You're welcome.

Greg

[JonathanX]

Salut François, I understand of what you want to accomplish and good for you if you do it to your satisfaction, I sail for the last 32 years fleuve St-Laurent up to Ontario lake every year and I want to tell you that you don't need that type of AIS or emergency. Just call cost guard and they will be on your spot withing no time and there is barely no boats traffic that could come to your way here in Canada. Now saying that, for the last few years I been playing with almost all the hardware you talking here and you could make it working at the very cheap price for the Arduino's, ESP's and even PI's. My goal was to control my RM ST4000+ and if ever defective I have my own made pilot control, as well I made a remote 4 buttons control (-1+1,-10+10, stanby, Auto). As at my age I hate to do programming so I use visuino.com software, it is a visual programming and it is free. Just on the last week I purchase an Ultrasonic Anemometer (wind speed/direction) and it just run fine with OpenCPN for the cost of US$139.00. That is what I am playing for the last couple days. Have fun and good luck on your decision.

[francois.lavoie]

@JonathanX:
Thanks for the tip about the visuino.com software. I will have a look at it surely. Though they work on the two other platforms, for now available only on win:
https://www.visuino.com/download


There is another one compatible with the three platforms, win, osx and linux:
Getting Started with ArduBlock | Ardublock



Thanks.

[EarlWer]

Originally Posted by JonathanX

I purchase an Ultrasonic Anemometer (wind speed/direction) and it just run fine with OpenCPN for the cost of US$139.00.

Part number & supplier?
I just bought a boat in Belleville and it would be nice to add an anemometer to the RPi4 that I will be installing.

[francois.lavoie]

Grove – GPS (Air530)
https://www.seeedstudio.com/blog/201...d-comparisons/

this module is capable of receiving more than 6 satellites at the same time and is able to work excellently even if there’s a very bad signal.

Price $17.21
https://www.digikey.ca/en/products/d...20022/12323450

[JonathanX]

Hi, here is the link for the product, contact Stefan, the whole thing chip UPS on my door cost CAN$225.00
https://www.alibaba.com/product-deta...673b151a019Ijo

François I have many type GPS modules you mention on my hand for the last few years for testing and so on and I decide not to use them as I use openCPN on 10 inch tablet that has internal GPS, to me the best one that I use on my laptop once in a while is the USB puck that you could purchase at Alie. for $12.00. The most practical instrument needs for East St-Laurence sailing is the Radar one as there is lot of fug down here.

[JonathanX]

François, I just look at Ardublock and I did found what it was and I rebember to look at it about 4-5 years ago, man.. if you touch Visuino you would never get rid of it. After getting use of it to program like @Kelkara circuit it would take you 5 minutes to do it.

[francois.lavoie]

@CarinaPDX:
I am on linux as my operating system, so gpsd and/or xgpsd

https://packages.debian.org/jessie/gpsd

is attractive for me than the u-center

https://www.u-blox.com/en/product/u-center


Especially, that I am unable to get the u-center installed on windows. When I try to install the software I get the error message:
u blox u-center setup activesync not found on this computer
there is no way that I could install activesync to get the u-center installed.


Under debian I was able to get data with the Grove gps air 530 module connected to my computer with a CP2102 usb to ttl device, but not with the GY-GPS6MV2 module.

The Grove 530 though a cheap choice at $12 CA, is set at the minimum to 9600 bauds and thus not amenable to 4800 bauds. Only the versions before 2014 could be set to 4800 bauds.

I will purchase a ublox 7M or 8M module, the 7M does not cover much whereas the 8M covers the 4 satellites options. The NEO-M8N at 12$ CAN is programmable, backward compatible withe neo 6n as they say, thus 4800 baud amenable. The problem is that it could take time before it is delivered. There is non in stock at digikey.


For the NEO 6M, I wonder if its only the module that is bad or if I am the one is unable to get data from it. I might buy another one to get my VHF-DSC GPS functional as soon as possible.


Thanks.

[JonathanX]

Salut François, if you have an Arduino or ESP board I could send you a Visuino file, compile it and load and look on serial 0 if your NEO6m work, you will see all the sequence comming from the unit every second, mine work fine here. what is your email address.