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Espruino is a JavaScript interpreter for low-power Microcontrollers. This site is both a support community for Espruino and a place to share what you are working on.
@allObjects
That's asking a lot of drive from a puck...
Looking at nRF52832 SoC (puck's heart, section 20.4 Electrical Specification p151ff, a 'high-drive pin can source/sink about 15/14mA within specified voltage range. This is barely handling the resistive load of one stepper coil, which for 300R is about 15mA. Another limit is the total drive/sink current a chip's IO system can handle (all outputs together because of 'internal wiring' and dissipation limits).
To give you some ideas, check GPS powered by Espruino pin(s) out. It is not exactly what you are trying to do, but it gives you some feel what MC pins can do...
Because of the challenges inductive loads pose, I would them always drive with a driver chip... that's what they are there fore in the first place, and not with a MC pin, especially when having to supply switching polarity, I guess (and not just pull down a coil at one end of which the other one is connected to supply voltage).
Next challenge is facing the limited capacity of the coin cell... you will pull (resistive) about 30mA from a 220mAh capacity. Duty cycle - and how smart the control is implemented - will of course define what you get out of the coin cell. But may be you have additional powering in mind.