While the Arduino has shields, the Raspberry Pi has its HATs, the Raspberry Pi Zero has pHATs, usually better known as “Bonnets,” and the BeagleBone has Capes, there really isn’t a standard name for Micro:bit expansion boards. But pretty much all of the boards connect via the Micro:bit’s 80-way edge connector and overall it’s all just a bit clumsier looking than other platforms.
However something we’ve started seeing with the Raspberry Pi Zero is the use of pogo-pins to attach boards underneath of the board using the test pads. Some of these shim boards even forgo the pins, needing to be soldered directly to the your Raspberry Pi like the Zero Stem.
So I guess, with all the awkwardness of edge connectors, it wasn’t going to be long before the idea made its way to the Micro:bit. Traditionally, battery backpacks for the Micro:bit are bulky — especially with most of them designed around a couple of AA batteries, they were never going to be small. Although that seems to be changing, with the arrival of “backpack” boards.
The battery backpack boards for the Micro:bit use metal standoffs to connect to the power and ground connections, allowing them to nestle more snuggly to the Micro:bit board than traditional battery boards using the edge connector.
There are a couple on the market right now, and they range in price and features from the Subsystems Rechargeable Backpack on Tindie at $25 at the high end, to MI:Power board at £5 (around $6.50) at the low end.
The Subsystems board has a charge control circuit, and a Li-Ion rechargeable battery, attaching using two 10mm metal standoffs on the
3V holes of the Micro:bit. While the MI:Power board uses a non-rechargable CR2032 coin cell battery, but does gave built in buzzer is connected via the
P0 hole—the default output pin when using the audio functions in Block Editor—using an additional stand off.
So far at least, I’ve only seen this backpack form factor used for battery boards. But I’m presuming it won’t be long until we see other expansion boards using it, perhaps adding some pogo pins—or soldering like the Zero Stem—to connect to the smaller pins on the edge connector? Of course, I haven’t thoroughly searched Taobao, they might already exist?