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I want to collect GPS data with a cellular-enabled micro-controller to help me find my drone if it gets lost. My drone has GPS, so I tried to connect to it. Many GPS break-out boards have the following connections:

  • GND
  • 5V/3.3V
  • TX
  • RX

Some of the time there are more, but these seem to be the essential ones. But, I'm studying a GPS module that uses only 3 wires. Take a look:

enter image description here

The red and black ones are power and ground. Must the remaining wire be TX?

I've been trying every way I can think of to tap into this GPS on my quad. I spliced into the 3 wires, but I only connected ground and what I suspect to be TX to my micro.

enter image description here

Also, at this point, I'm just curious.

I've studied the GPS a bit more and I can now see it has a compass and some other motion device. So it's not just a GPS board. It also had it's own micro controller managing all of these devices. I think the serial data on the wires I've tapped has been reformatted for the flight controller. It's gibberish in the arduino app.

At this point I'm ready give up and just put a second GPS on the thing! But before I give up I wanted to ask if there are any other methods I can try to listen to the GPS.

Thanks!

  • Well, the "RX" pin on the GPS modules usually is pretty useless; it allows, maybe, to change the baud rate, but the GPS usually just spits out the data on the other line. So if you don't have any info just try to listen on it at different baud rates (start with 9600 and 115200, then try the other standard values). If you don't get anything, then maybe they are using a custom protocol (the ublox there is serial, but there is a uC between). So, have a look where you bought it if they tell you the protocol, then search for any identifier on the board and look on the internet – frarugi87 Mar 23 '16 at 9:27
  • For anything like this you really do need a logic analyzer. That can tell you much about what the protocol is and allows you to decode the RS-232 coding (if that is what it is) or other protocol. You don't need to spend a lot of money - I bought a bunch of cheap chinese "USBee AX PRO" off eBay - couple of pounds each - and use the open source sigrok and pulseview with them. They absolutely rock. – Majenko Mar 23 '16 at 10:24
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    If you only need the GPS data you could solder a wire direction to pin 20 of the metal-caned sub-board (Blox Neo 6M) – Gerben Mar 23 '16 at 16:22
  • @Majenko I got zero results on ebay for "USBee AX PRO". I got a CY7C68013A board, but I had to replace the EEPROM to make it work as a Logic Analyzer. – Gerben Mar 23 '16 at 16:24
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    @Gerben Maybe it was DealExtreme I got them from? Ah yes, this is the one: dx.com/p/… – Majenko Mar 23 '16 at 16:28

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