Gemma MO with integrated with Soft Button and LiPo Charger

[HighlandRanger]

I would like some advice. Is it possible to integrate a LiPo battery charger into a circuit with the Gemma MO so that I can just connect a USB to my device to charge without removing the battery? I would also like to add a soft button to switch it off, and possible a second button to switch between two flash patterns on the Gemma. Thanks!

[dastels]

You can use a LiPo Backpack (https://www.adafruit.com/product/2124) getting 5v from a USB connection (e.g. https://www.adafruit.com/product/1833 or https://www.adafruit.com/product/4090). That'll give you in-place charging.

I did that with a CircuitPlayground Classic to make a coffee/tea timer. For on/off I used a TPL5110 (https://www.adafruit.com/product/3435): push the TPLs button to turn it on (then use one of the CPC's buttons to select time) and it will turn itself off when it's done (or a time hasn't been selected within a few seconds).

As for selecting lighting effects, that's a completely different issue.

Dave

[HighlandRanger]

Is there a guide anywhere for how to attach the backpack to the Gemma?

[dastels]

Not specifically that I'm aware of. But... 5v and G (ground) to the USB breakout and BAT and G to the Gemma battery connector using a JST 2-pin cable (https://www.adafruit.com/product/261). Be careful of the polarity. Don't be tempted to use Vout on the Gemma to pick up 5v when USB is connected, it's indirectly (through a diode) connected to the battery input so weird stuff will likely happen when USB isn't connected.

Dave

[HighlandRanger]

Is there a wiring diagram? I'm not understanding very well. I'm sorry.

[HighlandRanger]

Would it be better if I use the Trinket MO?

[HighlandRanger]

HEre's what I came up with. Does this look acurate?

Kaa Eyes.png (508.44 KiB) Viewed 257 times

[dastels]

There you go. That should do it.

If you use an ItsyBitsy instead you can mount the backpack directly onto the ItsyBitsy, as shown with with the trinketPro on https://learn.adafruit.com/adafruit-pro ... n-backpack.

Dave

[HighlandRanger]

This one? https://www.adafruit.com/product/3677

[dastels]

There are several ItsyBitsy models; I'd stick with at least the M0 https://www.adafruit.com/product/3727 if you're using C++/Arduino, or the RP2040 https://www.adafruit.com/product/4888 if you want to use CircuitPython.

Dave

[HighlandRanger]

Like this?

Kaa Eyes.png (448.83 KiB) Viewed 243 times

[dastels]

Except that the ground from the rings and button should connect to G (same as the backpack) not Vhi.

Dave

[HighlandRanger]

Ah, nice catch, thanks. I guess that pin changed from the other iterations of the board.

Kaa Eyes.png (447.57 KiB) Viewed 228 times

[dastels]

Looks good!

I don't know your physical constraints, but a 150mAh LiPo is pretty small for driving Neopixels. If a larger battery will fit, consider it. Or at least be prepared to if the 150 doesn't last long enough between charges.

Dave