CubeCell HW Damage, Still Alive, Uses?

#1

I was working on my CubeCell HTCC-AB01-v2 on a breadboard. I had an external battery BMS attached via I2C to the SCL and SDA pins. The ground pin slipped out of the breadboard and touched 3v3. Ever since, the device has been strange.

First off, any code I compile in Arduino IDE refuses to boot unless I short the Vext pin to 3v3.
Oddly, WASN’s firmware works without this hack, but that firmware is the only one I can get to work without the hack.

With the hack, one cannot flash a new firmware while Vext is shorted to 3v3, so I have to toggle the short when debugging in Arduino IDE. Also, for some reason Arduino IDE’s Serial Monitor won’t see any output, I have to use WASN’s configurator to see serial output.

On top of all of this, code that used to work before the incident does not work anymore. The LoRa chip seems to be broadcasting SOMETHING but it doesn’t look like a proper LoRa packet on SDR.

SDRSharp_tur772PStB

(UPDATE: Shorting Vext to 5v instead of 3.3v allows the LoRa chip to work correctly, so that still works)

The I2C is also bit weird, it can “init” hardware that’s not there, instead of returning an error. It then provides fake values (like -100v for the BMS). But if the hardware is connected, it can read it properly.

I tried testing LoRa with WASN’s firmware but I do not have a LORAWAN setup, and the heltec-documented AT+LoraSet command does not work (says no such command), so I cannot configure the parameters for LoRa such as the coding rate and bandwidth on WASN’s firmware.

Overall I am just curious if this CubeCell can be salvaged for anything since it does still have some life left in it, I’d hate to just toss it away.

#2

How much is your time worth? Sounds like you have a damaged device with unknown behavior, so if you are super curious and love to experiment, you might be able to figure out what works and what doesn’t.
But you kind of have to assume that it won’t always follow the documented behavior for what it’s supposed to do… So if you are trying to get something working, best to get a good device to work with also.

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#3

I was able to get it to fully work (except low-power mode, which just goes through the actions but can’t shut off VEXT itself) by shorting VEXT to VIN (5v). That fixed the LoRa and also Arduino code. Execution starts as soon as VEXT touches 5V, and stops again when VEXT is disconnected from 5V.

I still don’t understand why WASN’s firmware works without the VEXT short, but this isn’t a completely terrible setup. It would be nice to have the original control over VEXT but manual control lets me cut/pause execution whenever I please. (Like that time I forgot a delay() in my code and was spamming LoRa non-stop, I panicked a bit, lol). I might be able to rig up controlling VEXT over a working GPIO with a transistor, but yeah…

It mostly works, and is reading my DHT22 and INA219 without issues and sending the packet to my WiFi-connected Heltec V3 for further processing. So its good enough for me for now!

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