rhaine
Posts: 7
Joined: Wed Dec 09, 2020 2:34 pm

Garmin ECOMAP connected to RPi 4

Wed Dec 09, 2020 2:53 pm

I want to connect a Garmin UHD 63cv with my RPi using the shared data cable 2-wires (RX/TX) that the device provides. My goal is to use GPSD and write NMEA 0183 sentences to my RPi. I can connect the RX/TX wires from the Garmin directly to the GPIO serial pins and not have to fuss with serial-to-usb connection. Is that safe for the RPi? Idea of using a Serial-to-USB connection is to take you from 5v to 3.3v correct? Is wired direct connection a power issue w/RPi?

jayben
Posts: 329
Joined: Mon Aug 19, 2019 9:56 pm

Re: Garmin ECOMAP connected to RPi 4

Thu Dec 10, 2020 8:02 pm

It isn't a good idea; the signal levels and polarity will be wrong. If you want to use the Pi serial port, google 'RS-232 To TTL Converter'.

rhaine
Posts: 7
Joined: Wed Dec 09, 2020 2:34 pm

Re: Garmin ECOMAP connected to RPi 4

Fri Dec 11, 2020 12:38 pm

Thank you for responding. I did purchase a RS-232 to TTL Converter as you suggested. It uses the FTDI chip on the plug to do the conversion. Recommended for Raspberry Pi and is 3.3V TTL-232R compatible.

https://www.amazon.com/dp/B015ME2WKO/re ... UTF8&psc=1

FTDI: https://www.ftdichip.com/Products/Cable ... Serial.htm

Simple USB 2.0 (with the FTDI Chip) on one end and (3) wires on the other end. Ground, RX and TX. The Garmin provides a shared data connection of (2) wires (RX and TX). I grounded to the battery for the Garmin and then connected RX to TX on one wire and TX to RX on the other wire.

The RPi sees the connection as USB when I plug it in lsusb identifies FTDI. When I do a dmesg | grep -i usb it identifies the connection as ttyUSB0. So when I start GPSD with sudo gpsd /dev/ttyUSB0 -F /var/run/gpsd.sock all is good. Then I run sudo gpsmon /dev/ttyUSB0 which should start scrolling NMEA 0183 sentences and it is just a blank screen. If I plug in a simple GPS receiver, I can get NMEA sentences with no problems. Can't figure out why I don't get any data from the Garmin.

jayben
Posts: 329
Joined: Mon Aug 19, 2019 9:56 pm

Re: Garmin ECOMAP connected to RPi 4

Fri Dec 11, 2020 2:41 pm

You are confusing a USB RS232 device (with an FTDI chip) with a simple RS232-TTL level-converter (which has something like a MAX2232).

However, if you have a serial interface that works with other devices, but not with the Garmin, then either the problem is something simple like the baud rate or wiring being wrong, or perhaps something more tricky, e.g. the device doesn't emit NMEA sentences by default.

If that is the case, you need to get hold of a serial protocol guide for the Garmin device, which will tell you the commands to send, to get NMEA out.

rhaine
Posts: 7
Joined: Wed Dec 09, 2020 2:34 pm

Re: Garmin ECOMAP connected to RPi 4

Sun Dec 13, 2020 4:44 pm

The RS232-TTL level-converter you provided I researched. I believe its MAX3232 and I found a connector that'll do the conversion.

https://electropeak.com/rs232-ttl (Please confirm this is the type of hardware connectivity you are suggesting)

In answer to the questions in your post:
Yes, NMEA 0183 sentences has to be enabled ON in the Garmin. Yes I do have them turned on and there are no serial protocols or commands, it just broadcasts NMEA regardless of whether you have ON/OFF in the Garmin.
Sentences are transmitted every second if NMEA is turned on in the Garmin setup which I've done. Garmin's shared data is available with RX and TX wires that I'm attempting to connect via a hardware solution that will compromise the power on the RPi.

jayben
Posts: 329
Joined: Mon Aug 19, 2019 9:56 pm

Re: Garmin ECOMAP connected to RPi 4

Sun Dec 13, 2020 9:02 pm

If the baud rate is correct this should work, however I've just noticed you say "I grounded to the battery for the Garmin", which is a bit strange; why haven't you used the ground pin on the RS232 connector? Also, you haven't mentioned applying 3.3V power to the RS232-TTL converter.

You can do a quick test of the converter by linking to Tx & Rx pins, then running a terminal emulator, and checking that any keypress is echoed back.

If none of this works, I give up!

rhaine
Posts: 7
Joined: Wed Dec 09, 2020 2:34 pm

Re: Garmin ECOMAP connected to RPi 4

Wed Dec 30, 2020 4:13 pm

jayben I appreciate your input. I'm going to try and make this simple.
I had connected a USB GPS dongle to my Raspberry Pi and receive GPS data with no problems. GPSD worked.

I then connected a simple TTL to Serial Converter as you recommended to my Garmin TX/RX/GND wires. My simple converter has a small led light that shows the pulsing and receiving of NMEA sentence data every second as it should. The little converter has a female serial port to which I connect a simple Serial to USB cable.

Before connecting the TTL to Serial converter I ran lsusb and it shows typical connections to the RPi of keyboard/mouse etc. I plug in the USB from the TTL converter and run lsusb again it now shows one more item in the list: Future Technology Devices , FT232 Serial (UART) IC
Note this converter uses the MAX3232 control chip.

I cannot get the NMEA data. When I run dmesg | grep tty it shows ttyAMA0 / ttyS0 / and ttyUSB0
Which of these should I use when i execute the GPSD command?

Kandersen
Posts: 1
Joined: Tue Jan 26, 2021 8:38 pm

Re: Garmin ECOMAP connected to RPi 4

Tue Jan 26, 2021 10:49 pm

Hi Rhaine

Hi, I can't help you, but I'm pretty sure you can help me.
I'm an old programmer who just got an RSP 4. I've been using Arduino for a few years.
I would like to use a GPS module (which I bought for the Arduino) which is connected to the Tx/Rx , 5v and ground.
but I can't get it to work, receive no data. I have tried with a python loopback program, to see if that is sent and in particular received something on Rx. It doesn't work either.
I have dusted the internet thin and found all sorts of fixes for Config.txt and cmdline.txt. None of this has been allowed to work either.
You write that you have a GPS module that works, so now I hope you can tell me what it takes to make it work.

yours sincerely

Kent

rhaine
Posts: 7
Joined: Wed Dec 09, 2020 2:34 pm

Re: Garmin ECOMAP connected to RPi 4

Mon May 10, 2021 4:59 pm

Kent,

I apologize in not responding for so long. I've used the G-Mouse by Stratux. The VK-162 still available. Here it is on Amazon - https://www.amazon.com/dp/B01EROIUEW/re ... DD31KFW0A9

No worries as to the TX/RX as this has a long cord and USB and is plug/play with Raspberry. No setup required. Plug it in and GPS will be readily available to you w/GPSD etc. The module or pod is magnetic and popular use is to attach to your vehicle, plug in to a working RPi 4 and you've got GPS wherever you go.

Bob

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