This forum uses cookies
This forum makes use of cookies to store your login information if you are registered, and your last visit if you are not. Cookies are small text documents stored on your computer; the cookies set by this forum can only be used on this website and pose no security risk. Cookies on this forum also track the specific topics you have read and when you last read them. Please confirm whether you accept or reject these cookies being set.

A cookie will be stored in your browser regardless of choice to prevent you being asked this question again. You will be able to change your cookie settings at any time using the link in the footer.

Thread Rating:
  • 0 Vote(s) - 0 Average
  • 1
  • 2
  • 3
  • 4
  • 5
NMEA 0183 Data from Lowrance Chartplotter Received as Garbage
#1
Hi all,

I am exploring OpenPlotter with a test system at home.  I've attached my Lowrance Elite-4 HDI chartplotter to an RS-422/485 -> USB adapter using an FTDI chip, following the pinout in the Lowrance manual (for RS-422; RS-232 instructions are also offered).  When connected to my Pi and recognized by OpenPlotter, I don't seem to be able to get any NMEA data coming through in the Kplex diagnostics windows.

When monitored in a serial console, I can only see garbage/gibberish like this transmission:

Code:
[Æ’}Ìù;;;;;;;;;;;;;[ªvVoÔ[◊.ùùùÀ{Vñ6-V÷ÏvmÎ⁄.6Vˆl-ŸŸŸv-üˆ∂V.vmµmvVoÔ[◊µUkù;;;;;;;;;;;;[õ6VoÔ[◊µU+ù˚˚ˆ∂V.vmu-ˆ¨ñ6-V÷ÏvmÎ⁄.6Vˆl-ŸŸŸv-uÌ6ÌvÌ6ÌvÌ÷ˆ∂ˆˆv≠ˆ6-v-µ≠6ïÎ∑q_qq}ßüüüõïëßôèïô£ôïçüßcßüëìïè£ëìóüßQßüßüßçç£üüßïôßeßßßß´ùùÂÎ∑q_qY}ß}ßùßßßßßßßßßßßßßßçç£üüßçç£üüßü£üü´õyÂÎ∑q_qYSßùßùßùßùôèßôïßõõõß´óìÂÎ.

I have matched the baud rate at 4800, but have also tried several other pairs as I'm able to change the baud rate in the chartplotter.

Could anyone suggest what might be the problem?  Am I using the wrong kind of adapter, for instance?  I don't seem to be able to tease any useful data out of the connection, and I'm pretty confident that I've wired correctly.

Here are the components:
Raspberry Pi 3 Model B
OpenPlotter 1.2.0 Alpha
DSD TECH USB to RS485 RS422 Converter with FTDI FT232 Chip: http://a.co/d/2woKtBi
Lowrance Elite-4 HDI

Thanks for any suggestions!
Reply
#2
As an initial test, open a terminal and use the "cat" command on the interface. For example, if the interface you are connecting to is ttyUSB0, then open a terminal and type "cat /dev/ttyUSB0". Look at that to see if you are getting recognizable NMEA strings.

If you are seeing good NMEA strings, then it's probably still an issue with speed. If not, then your interface is a good place to start looking.
Reply
#3
looks like the wrong baud rate
Reply
#4
Thanks for the speedy advice, abarrow and jim321!

(2018-11-18, 05:33 PM)abarrow Wrote: As an initial test, open a terminal and use the "cat" command on the interface. For example, if the interface you are connecting to is ttyUSB0, then open a terminal and type "cat /dev/ttyUSB0". Look at that to see if you are getting recognizable NMEA strings.

If you are seeing good NMEA strings, then it's probably still an issue with speed. If not, then your interface is a good place to start looking.

cat output looks like pretty much the same thing I was seeing in the serial terminal, above.  The chartplotter is definitely sending messages; I'm just unable to interpret them.

When you suggest looking at the interface, do you mean the USB com port hardware? I'd read people had positive experiences with the FTDI chips, so I thought this would be a good choice.


(2018-11-18, 06:24 PM)jim321 Wrote: looks like the wrong baud rate

That was my initial assumption, but the chartplotter has selectable baud rates, and 4800 was the default.  I also set 4800 in OpenPilot's serial interfaces manager.  I believe 4800 is pretty typical for NMEA 0183, but I also tried other pairs like 38400 to no avail.
Reply
#5
Do you have correct polarity?

You can use an LED to check: https://digitalyachtamerica.com/download...4129&ind=0


Sent from my iPhone using Tapatalk
Reply
#6
(2018-11-19, 06:23 AM)tkurki Wrote: Do you have correct polarity?

You can use an LED to check: https://digitalyachtamerica.com/download...4129&ind=0


Sent from my iPhone using Tapatalk

Thanks for the feedback and inspiration, tkurki!  The LED trick resulted in no illumination so I tore out the wires (which I had carefully aligned following instructions from both Lowrance and the RS-422/USB converter) and started attaching different combinations.  At the third or forth iteration, success! I am now getting good GPS and other NMEA data in and out of the Raspberry Pi, OpenPlotter, and OpenCPN!

For posterity, here is the configuration that is working for me:

Code:
+--------------------+--------------------+
|      Lowrance      |      DSD Tech      |
|    Elite-4 HDI     |   RS422 Converter  |
+--------------------+--------------------+
| Blue (TX_B)        | 1 (TXD+)           |
+--------------------+--------------------+
| Yellow (TX_A)      | 2 (TXD-)           |
+--------------------+--------------------+
| Green (RX_B)       | 3 (RXD+)           |
+--------------------+--------------------+
| Orange (RX_A)      | 4 (RXD-)           |
+--------------------+--------------------+
| Shield/Ground      | 5 (GND)            |
+--------------------+--------------------+
Not sure if I just don't understand the wiring or if one or both sides is mislabeled, but this is currently working, bidirectionally.
Thanks again all for the support.
Reply


Forum Jump:


Users browsing this thread: 2 Guest(s)