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GPS clock with multidrop databus

Using GPS modules in variouse projects I started to get a shortage on space in the shack window. And because a new project arrived who also need GPS for synchronization and timing, I wanted to look for a good base setup which could be shared between various projects. That how the GPS clock with multdrop databus came to mind.

Basiclly it's build out of the following components :

  • good quality GPS receiver with external antenna
  • arduino based GPS clock which also TX a stream of decoded GPS data (differential driver TX)
  • a raw GPS datafeed and a 1pps output (both differential driver TX)


The GPS receivers contain use differential RX buffers to connect to the multidrop bus. For the multidrop bus CAT6 cables can be used or any other twisted pair and shielded cable.



On this page new idea's and the progress about this system will be published.

We got started

Because I broke my utc clock this project was activated again. From the spareparts I had on stock the first steps are made. The basic building blocks are :


  • Arduino MEGA 2650 (it's overkill but hey it works for development)
  • Large 4x20 LCD display (for now with I2C lcd adapter)
  • NeoBlox6 GPS receiver
  • BME280 (for temperature, humidity and pressure measurement).
  • DS3231 RTC (backup clock but will be synced to the GPS)


The software (which is still work in progress) I have wrote myself published on my github page (link). This weekend I want to buy and add the MC3487N and MC3486N RS422 bus driver and receiver. Then it will have a multidrop signal bus (rs422 based) to allow other gps enabled devices to use the nmea data stream and the 1pps signal. 
The first device what will be added is a large (8 cm high) 4 digit 7 segment display which will be my new UTC clock in the shack.

Below are some pictures of the experimental setup. A video with commentary can be found on a post on my instagram account (link).

The software now is showing :

  • UTC date & time
  • Locator grid
  • Sat count
  • Latitude & Longitude (in Dgr en DMS)
  • Temperature, Humidity & Pressure.




Another step forward

When the 4x20 blue LCD arrived I couldn't resist starting on the building of the final case. Big advantage of the I2C LCD controler. Just extend the wires for testing. The push buttons aren't connected yet.

And again another step forward

Everything is starting to get together. The larger MEGA2560 board is replaced by the final Robotyn MEGA 2560 (Embedded).

Next steps : tapping the 1pps signal to a interrupt of the Arduinoboard.

To be continued.


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