Occasional dim LED on Boron, either won't boot or won't connect

So I’ve had a Boron LTE running for a couple months. Repurposed it (no firwmare in either case, just a new case and power supply) and sometimes it either:

  • Doesn’t boot, LED is dim
  • Boots to searching for cell signal (flashing green), but before attempt to connect (flashing cyan) the LED briefly dims and unit reboots (endless cycle)

I tried:

  • Only 5V power supply to USB pin
  • Only LiPo battery (from a Boron 2/3G)
  • Both power supply and battery
  • A different power supply

Monitoring power, strong 5V in all cases, no dips with a min/max Fluke meter. I monitored mA when it does connect; start at about 35 (flashing green), jump to ~110 during (flashing Cyan), fall down to 20 or less (breathing Cyan).

Even odder, when I put this Boron (with no battery) alongside Electron 3G (with LiPo battery) in a parallel powered circuit via perfboard (one 700mA power supply) it ALWAYS boots - just doesn’t boot by itself. I continuity/resistance tested the circuit with the same Fluke meter but don’t see any stray leakage anywhere, and doubt Electron is acting like a capacitor since Boron doesn’t always boot by itself with a charged LiPo battery (since no pins output voltage when LiPo connected).

Seems to be no rhyme or reason.

Well I think it’s the test bed…

I actually have 3x units next to each other (signal surveys):

  • Boron LTE, Electron 3G on one power supply
  • Electron 2G on another power supply
  • Both power supplies share one power cord to line AC
  • Ground wire of power cord tired to both power supply ground wires (-)
  • Reset pins of all units share the same reset button

Fun fact, pressing any individual reset button resets all units since it’s a momentary contact to ground (and all reset pins are tied together).

Some culprits might be sporadically tripping the reset pin on Boron:

  • The other Electrons are slightly conductive through their reset pins (like mega Ohms)
  • Simply inserting Boron (powered by battery) into the test bed (with NO power supplies, power cord ground, nor Electrons connected) will sometimes cause a reset - so perhaps the slight capacitance or difference of potential on the perfbord

In short I think the Boron has a VERY sensitive reset pin tolerance.

Ok, final answer,

True I think Boron has a hairline trigger reset pin… because just touching a connected device with a voltmeter (yes Volts, not Amps) will reset the device. I was just able to measure the “standing voltage” upon pin touch (I have a min/max Fluke) at 0.2V, and that too for like a ms. Almost drove me crazy because problem 1st showed up when I hot-swapped Boron into a board with female headers (no i/o going).

Long story short don’t think you can really hot-swap these. :open_mouth:

What made you think they were capable of Hot-Swapping?

The “hairline trigger” phenomenon is probably due to some type of damage caused when you plugged your device into a daughter board with the power on.

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Maybe, but not really because this happened before I hot-swapped. Why? Because I thought they were already damaged.

Do you see this too?