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Thread: GPS communication with serial port

  1. #1
    Junior Member
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    GPS communication with serial port

    Hi everyone!
    I'm trying to get some data from the serial port of a M9N GPS, a Mateck GPS module built for ardupilot use(http://www.mateksys.com/?portfolio=m9n-can). I'm trying to read from UART port without success.
    In the GPS datasheet is mentioned as an MSP protocol, but I can't read any sensed output even with a simple serial monitoring activity.
    The wiring is checked, and if I invert rt and tx it cont read anything, otherwise it reads only a few numbers /sec.
    I'm using a teensy 3.6 or a 4.0. with the first board, I've even tried to use UAVCAN without success.
    Thank you for any idea

  2. #2
    Senior Member+ defragster's Avatar
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    In addition to Rx and Tx being right they need a common GND. And of course the right baud rate.

    And for T_3.6 and 4.0 it must be using 3.3V levels on the UART pins.

    Not sure about the GPS in use. If it will be sending data by default or if it is waiting for a command?

    Need to be sure the GPS has enough power as well for it to function - assume it has some 'function indication' LEDS showing it is powered and locked to satellites?

    and : "reads only a few numbers /sec." suggests that is proper connection order for Rx/Tx -

  3. #3
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    5v and GND are taken directly from the teensy board, I'm sure that the signals are 3.3v, checked with an oscilloscope.
    I'll find if I must send a specific command, but I've tried with a simpler GPS, a beitian bn-220, but I have the same problems.

  4. #4
    Senior Member+ defragster's Avatar
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    To test the Teensy perhaps wire Serial# pins in use to another set of UART Serial#? pins and confirm they are functional.

    Open both Serial# with Rx and Tx Crossed - could also cross on the same Serial # port - then send and receive some messages to confirm function

    Or do the same with a second Teensy if one handy

  5. #5
    Senior Member brtaylor's Avatar
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    MSP is a binary protocol, I'd be tempted to try UART2, which should be NMEA and at least human readable.

  6. #6
    Senior Member PaulS's Avatar
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    Quote Originally Posted by brtaylor View Post
    I'd be tempted to try UART2, which should be NMEA and at least human readable.
    That's what I thought as well until I found out that the RX2/TX2 pins are not exposed on this module.

    Paul

  7. #7
    Senior Member+ mjs513's Avatar
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    Was just looking at module and it looks like data is going to be coming out through the CAN connections if I had to take a guess.

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