connect with usb to COM-NB-IOT-MODULESIM7020G fails

  • Hi,
    I cant get the USB port on sim7020g modem working. I just connect my PC with a terminal emulator.
    The board powers up (red led) and blinking blue NET LED.
    However I only get garbage characters on my terminal as if the speed was wrong.
    I have tried all speeds without success. Default is 115200 8N1.

    It generates 2 USB-devices as other modems like SARA R410 do.
    Should it be possible - any clues ?


  • Hello @olavk

    I assume you mean the USB port on the green board plugged into the COMX.NB-IoT module, correct?

    If yes, then according to the SIM7020G Hardware Design Guide - chapter: 1.4 Functional Overview the USB port is meant for debugging. Maybe that means it cannot be used to issue AT commands?


  • Thanks @felmue - Yes I mean the USB on the breakout board. The referred manual states : 'The SIM7020G contains a USB interface compliant with the USB1.1 specification as a peripheral'.
    And my intention was indeed to do debugging to see if the modem would connect to the network with my SIM before I start to connect it to my Arduino.

    Anyone that have a connection diagram for how to connect this breakout-board to an Arduino (MKR Zero),
    as I don't want to use the M5 Stack wrapping.

    So I have pins PWR, GND and P/G on one side and VIN VEXT and VTTL on the other side.
    Could I expect P/G to be the pin to trigger to power on/off ?

  • Hello @olavk

    no, I don't think P/G is the on/off trigger. It seems to be connected to GND. I think PWK is the power key.

    Have a look at the COMX schematic. You'll find this:

    • P/G : is connected to GND
    • GND : is connected to GND
    • PWK : is connected to EN
    • RXD : is connected to GPIO17, GPIO0 or GPIO17
    • TXD : is connected to GPIO16, GPIO5 or GPIO15
    • VIN : is connected to either 5.4 V or whatever is provided at the DC in
    • VIN : dito
    • VTTL : not connected
    • VEXT : not connected

    How exactly this translates to an Arduino MKR Zero I cannot tell. I don't have one to try. Sorry.


  • Thanks @felmue,
    I have now got the card powered by following your observations :
    connecting 5v to VIN, GND to GND, TX to RXD, RX to TXD
    I don't need to trigger PWK to get the modem operational.
    The modem don't connect to the network, but that's another problem..