RFM69HC doesn't want to send/receive?



  • Hi there, maybe someone here can help me:

    I've got two RFM69HC 434Mhz, connected to two Arduino Nano 3 clones.

    The code I use for testing is this:
    https://gist.github.com/solars/44b2398e62d07e29314538a70579663f
    (it's from sparkfun: https://learn.sparkfun.com/tutorials/rfm69hcw-hookup-guide/running-the-example-code)

    When I enter something in the serial console it seems to be sending. The LED flashes quickly.
    However, there is nothing received on the other side. If I eneable ACK I just get the 'no ack received' msg.

    Can anyone spot the problem? Is it maybe because I don't have a HCW, any settings wrong?

    Thank you very much



  • well - the blog post I used for the wiring missed the detail that the RFM69 does not seem to be 5V tolerant (inputs).

    Can anyone tell me:

    a) if it is damaged if the inputs had 5V
    b) how I can adjust the levels, can I do this with resistors or do I need more?


  • Mod

    It might have survived but it is hard to tell. A broken module can behave in any way.

    I would use a logic level shifter. There is a link on this page: https://www.mysensors.org/build/connect_radio#wiring-the-rfm69-radio



  • @Christoph-Blank said:

    well - the blog post I used for the wiring missed the detail that the RFM69 does not seem to be 5V tolerant (inputs).

    Can anyone tell me:

    a) if it is damaged if the inputs had 5V
    b) how I can adjust the levels, can I do this with resistors or do I need more?

    I made the same mistake, while connecting the modules VIN pin to the Arduino's 3.3V rail, I failed to read that the RFM69's pins aren't 5V tolerant. After I figured out how to make another pair of RFM69 modules work together, this time at the correct voltage, I tried the first to if they were fried. They weren't. As soon as I connected them to a 3.3V Arduino they worked like a charm. So it's very likely that yours are fine to.
    As for the correct wiring, some are using voltage dividers to lower the signal pins voltage down to 3.3V. Others are using logic level converters. Me, I was lucky engough to have a couple of chinese 3.3V Arduino Pro Mini boards ordered a long time ago and never used since. For minimal clutter, I'd suggest using the same setup. The cheapest 3.3V options are the Arduino Pro Mini (my model) but you'll also need some USB to TTL dongles (the ones having a DTR pin) to program them. Or you may use something like:
    http://www.ebay.com/itm/Pro-Micro-3-3V-8M-5V-16M-atmega328-Replace-ATmega128-Arduino-Compatible-Nano-/172446438226
    but notice that this one doesn't use the ATmega328 chip but ATmega32U4 and that will require these lines of code at the top of your sketches:
    For MySensors 2.0

    #define MY_RF69_SPI_CS 8
    #define MY_RF69_IRQ_PIN 7
    #define MY_RF69_IRQ_NUM 4
    

    For MySensors 2.1.0beta (RSSI report added amongst a lot of other improvements)

    #define MY_RFM69_SPI_CS 8
    #define MY_RFM69_IRQ_PIN 7
    #define MY_RFM69_IRQ_NUM 4
    

    Note the slight difference between the two.


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