About the Nmea1ST

This forum is for discussing hardware (electronics) and software design aspects of multiplexers in general.
Post Reply
Luis Sa
Site Admin
Posts: 845
Joined: Thu May 04, 2017 4:12 am

About the Nmea1ST

Post by Luis Sa » Tue Mar 30, 2021 1:55 am

Hello,

The Nmea1ST is a bridge between SeaTalk1 and Nmea0183. It runs on a ESP32 development module. It needs to be fully tested and some conversions from the Nmea to SeaTalk1 direction need to be added. I publish here the software and the schematics of a possible hardware.

The software needs to be compiled and flashed using the Arduino IDE. In order to do that you should unzip the 7 ino files contained in the ZIP to a folder with the name of NMEA1ST that you need to create inside your Arduino sketchbook folder.

In a following topic I suggest a simpler circuit to run the software for testing purposes.

Regards, Luis
Attachments
Schematic_Nmea1ST.pdf
(50.23 KiB) Downloaded 629 times
NMEA1ST.zip
(22.04 KiB) Downloaded 587 times

Luis Sa
Site Admin
Posts: 845
Joined: Thu May 04, 2017 4:12 am

Re: About the Nmea1ST

Post by Luis Sa » Thu Nov 25, 2021 7:56 pm

Hello,

If you can use the USB port (that exists in most ESP32 development boards) as the Nmea0183 port you can run the software in a simpler circuit without the 12V to 5V voltage regulator, the MAX485 driver and the HCPL2731 optocoupler. Here is a possibility:

1-transistor.jpg

Unfortunately this circuit is not good as it does not allow the data line to go to 12V when Q2 is OFF. I am thankful to Dagnall for pointing this error to me. The circuit on Thomas Knauf document is not applicable here as we need GPIO18 to see a HIGH (3V3 maximum) when Data line is idle at 12V. One possibility that I did not test, but could work is this:

2-transistors.jpg

A further simplified circuit that I use for testing and development purposes (excluding the SeaTalk1 bus collision tests) is shown in the following picture:

st-4.jpg

In order to use this circuit I set the variable LoopBack as shown:

Code: Select all

boolean LoopBack = true;              // Normally when you transmit data on the SeaTalk bus you stop

and I send Nmea0183 sentences from a file to the Serial Port (USB) of the ESP32 module. These sentences are converted to SeaTalk1 datagrams and sent serially on pin GPIO17. This signal is inverted by the transistor and read again at pin GPIO18. The datagrams are converted to Nmea sentences and send out at the Serial Port and shown in a monitor or stored in a file. This is a picture of the actual circuit:

st-5.jpg

Regards, Luis

zcjs23
Posts: 1
Joined: Wed Mar 01, 2023 9:38 pm

Re: About the Nmea1ST

Post by zcjs23 » Thu Mar 02, 2023 10:36 pm

In NMEA1ST schematic isn't there an error on D3?

Luis Sa
Site Admin
Posts: 845
Joined: Thu May 04, 2017 4:12 am

Re: About the Nmea1ST

Post by Luis Sa » Sun Mar 26, 2023 1:35 am

Hello,

I just saw your post now. I am not sure what you refer to D3. This post was about the initial test circuits I used for the development of the NMEA3WIFI multiplexer. You can see present circuit diagrams in the right forum.

Regards, Luis

Post Reply