Use AT commands over UART on mDot

Home Forums mDot/xDot Use AT commands over UART on mDot

This topic contains 6 replies, has 2 voices, and was last updated by  David Sun 2 months, 2 weeks ago.

Viewing 7 posts - 1 through 7 (of 7 total)
  • Author
    Posts
  • #27574

    David Sun
    Participant

    Hi, so I’m trying to use the mDot as a LoRA module for another microcontroller through the use of AT commands.

    I’ve hooked up my UART pins to pins 2 and 3 of the mDot for communication and try sending “AT” among other failed attempts, and I get no response from the mDot.

    I can tell that the mDot is on, as I am measuring a current draw through a multimeter, so I’m lost at what the issue might be.

    It is possible to use the mDot like a separate module and send packets over LoRA using just the AT commands sent over the UART pins on the default firmware, right?

    I don’t have a development board, so I can’t simply plug the mDot to USB.

    #27577

    Hi David,

    Are you sending commands at 115200bps? Did you connect ground?

    Leon

    #27579

    David Sun
    Participant

    Hi Leon,

    Yes, my baud is 115k and I connected ground. I can verify that it is not an issue with UART on my main microcontroller, as I can communicate with a different microcontroller just fine over UART using the same baud.

    So I recently looked under an oscilloscope on the Tx pin of the Mdot and there wasn’t anything coming out, despite it being powered on and receiving a UART signal from my main one.

    Maybe I have to reflash the firmware?

    #27580

    Hi David,

    If the AT application is not loaded, that could be the issue.

    The reset line has a weak pull up on it. So that should be fine.

    Leon

    #27582

    David Sun
    Participant

    Hi Leon,

    So I reset it and checked under an oscilloscope again.

    It seems that I am getting a response, but it is a very low voltage: not high enough for my main microcontroller to identify as a UART signal.

    Any ideas on why that might be? I am just sending “AT” to see “OK” from the Mdot. See picture attached.

    oscilloscope output from Mdot

    #27590

    Hi David,

    Please measure the voltage you are providing to the mdot. VDD is pin 1. The voltage needs to be in the range of 3.3v-5v.

    What voltage is your host board expecting? Is it a direct connection to the UART… no transceiver or level shifters?

    Kind regards,
    Leon

    #27591

    David Sun
    Participant

    Hi Leon,

    VDD is 5V, which I confirmed to be the case on the scope.

    It is indeed a direct connection to UART.

    Also, I used another mDot in the meantime with the same microcontroller and connections, which sent back the “OK” correctly.

    So I’m convinced this is definitely an issue with this particular mDot.

Viewing 7 posts - 1 through 7 (of 7 total)

You must be logged in to reply to this topic.