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Thread: Teensy4.1 LoRa Module DIO0 does not work on pin 8 but works on pin 25. Why?

  1. #1

    Teensy4.1 LoRa Module DIO0 does not work on pin 8 but works on pin 25. Why?


    I'm working on my Solartracer / Weather station project.
    Goal is to have a Solarpanel which faces towards the sun and follows.
    I use a Teensy4.1 for this project. There are several sensors attached and finally the data will be transferred by an Adafruit LoRa module from time to time.
    It is this Adafruit Module. I have already ordered a PCB which I have designed by myself. But now I have an issue that the LoRa module doesn't work.

    Here are is the error which is thrown:
    Packet queued
    .pio\libdeps\Teensy_SolarPanel_Geert\MCCI LoRaWAN LMIC library\src\lmic\radio.c:1065
    I made a test.
    Removed the the level shifter and changed the DIO0 LoRa module connection from pin 8 to pin 35. Now the LoRa module works fine.
    But I don't understand why exactly that it don't work as long as DIO0 is on pin8.

    Plot of the schematic is here or attached to this post.
    And the project can be found on my Gitlab site.

    When I look at the pinout map from the Teensy4.1, I see that pin 8 is also labeled as sda0 (lowercase). Normally I use the pin 18 for SDA0 (uppercase).
    Does anyone know why pin8 is labeled with sda0? I did not found useful information about this. Is this pin like shared or something similar?
    Therefore I write this post to find a explanation about, why the other pin works and what it is about the sda0 pin8.

    Best regards

    Attached Files Attached Files

  2. #2
    Senior Member+ defragster's Avatar
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    Feb 2015
    Looking at the T_4.1 card here pin 8 is not labelled as SDA/{SDA0}. SDA/{SDA0} is pin 18? And that is on the opposite side of pin 8, the same side as pin 35.

  3. #3
    I know, on the card is pin 8 not labelled as sda0.
    But there are also this pinout cards form KurtE in this github repository.
    In this pdf, to be exactly.
    In one of those cards

    Oh no. I've just recognized that I've made a type on the thread title. There it should be also pin 35 and not 25.
    But I don't see an option to edit.
    Last edited by SimonBoonstra; 05-21-2022 at 10:55 AM. Reason: additional information.

  4. #4

    I found the mistake. Unfortunately I have used pin 8 twice in my test setup. Therefore there was a conflict.
    Now I have corrected the setup and everything works fine.

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