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Trouble initializing XBee3 LTE-M

Home Forums Mayfly Data Logger Trouble initializing XBee3 LTE-M

This topic contains 5 replies, has 3 voices, and was last updated by  Sara Damiano 5 days, 19 hours ago.

  • Author
  • #12612


    I recently successfully set up a MayFly with GPRSbee radio. It works great.

    I’m trying to get a second MayFly working with the Digi XBee3 LTE-M radio. This is on hologram, using a brand-new SIM card, which I understand should be possible. I’m not sure if I’m getting to that point, since even initializing the radio doesn’t seem to work 100%. I understand there is no soldering needed with this radio, and there is no JST connector as there is on the GPRSbee, so I’m not sure if there is a power issue… Anyway, with

    #define TINY_GSM_DEBUG Serial

    enabled, I’m getting output like this:

    So far, so good. Then, when trying to sync with NIST, I get:

    And then lots and lots of NO RESPONSE! lines until the 120 seconds is up. Am I missing something major here? Thanks.

  • #12613


    OK, looking at the GitHub issue, it looks like I may need to Solder SJ13 after all…?

  • #12615

    Shannon Hicks

    The Mayfly’s bee footprint was originally set up to only power modules that require moderate current supplied to the Vcc pin of the module, such as Xbee RF modules (900Mhz and 2.4Ghz), Bee wifi, and Bee bluetooth. There are even GPS modules with the Bee footprint that work great on the Mayfly. Then when we started using 2G and 3G cellular modules from SODAQ, they have their own separate JST sockets for connecting them directly to the LiPo battery, thus supplying sufficient voltage and current (they require ~3.7v and up to 2A). But other brands of cellular boards, like the Digi 4G board, don’t have the external power connection option, so the only way to power them is through the Bee header on the Mayfly, which is why I added the SJ13 option on the latest v0.5b Mayfly boards. So just cut the small trace that’s connecting the center pad of SJ13 (labeled BEE_Vcc) to the 3v3 pad, and put a solder bridge joining BEE_Vcc to the pad labeled LIPO.

  • #12617


    Thank you Shannon.

    OK, I cut the trace and confirmed no continuity between BEE_Vcc and 3v3 at SJ13. Then I made a solder bridge between BEE_Vcc and LIPO. I have ~4.1V between GND and LIPO/BEE_Vcc.

    The modem powers up and is evidently powered by the battery now but I still end up with the NO RESPONSE messages…

  • #12621

    Sara Damiano

    I’ve usually seen that “no response” pattern with the 3G XBee’s without the solder jumper. I’ve assumed it was them “browning out” as they tried to connect to the internet. With those, switching the solder jumper seemed to fix the problem. Have you been able to connect to the internet at all with the LTE-M XBee? Is it working attached to a computer with XCTU?

  • #12641

    Sara Damiano

    I’ve spent more time fiddling with the LTE-M XBee and I’m seeing the same results.

    It’s a hardware problem, not software; the modem really does stop responding. I wonder if it’s that there’s not enough capacitance along the power line causing very short voltage drops even when it’s tied right to the battery. The user guide for the LTE-M XBee specifically warns that the main control board on the XBee can become unresponsive after power dips and will need a full power-cycle to get it back. Oddly, though, I’m having it start responding again without actually power cycling it.

    I have a Skywire development board that has more capacitance on the power line. I’ll fiddle with it and see if I’m having the same issues.


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