New 1W DIY variant: Xiao nRF52840 + Ebyte E22-900M30S

Wanted to share a new variant I have been working on for the last several weeks. It pairs the Xiao nRF52840 with an Ebyte E22-900M30S. For me this was sort of a holy grail as it combines the Ebyte’s 30 dBm Tx power with an idle power draw that’s not terribly far off from that of a RAK 4631, and is also pretty compact.

Looks like my PR was just merged (thanks @thebentern!) so the variant can be found here. Included there is a short how-to doc ( which details the steps needed to get it running. I also drafted up a basic PCB for this setup which is here. It’s pretty easy to wire up on a protoboard too; the pics below are of an early build on an Adafruit “small tin” perma-proto, which is a near-perfect size.


I’m considering this very configuration. Are you planning to develop a carrier PCB with onboard power and charging circuits?

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Yes indeed. I have a first attempt that integrates the MiniBoost and JST/switch circuits into the schematic (instead of using the breakouts) but even better would be to include a solar charge controller of some kind – maybe even your LTO setup? Though I know that’s still a work in progress. In any case, I’d be psyched to collaborate on something to that effect!

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I’ll reach out on Discord. 3 of us are actively working on something like this. If we use the CN3791 battery IC it could handle charging from USB and from solar (li-ion only). The TPS61023 IC looks like a good choice to integrate on the board.

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I’ll give one of these boards a try, thank you. I have some IP2312 units coming, which are also rated to run at 2A, but I just ordered a couple C3791 based boards to try as well. TY.
CN3791 Datasheet
Looking at Figure 1, it would be nice if any manufacturer placed a jumper or switch between R1 and D3/D4 - the ability to turn off the indicator lights, without using a soldering iron, is a must-have.

Agreed. Most of the time these boards are installed in an enclosure and the charging light is unnecessary and wastes power.

I’m currently building a solar charger module using the CN3795 and I won’t include a charging LED.