Snowbird Core 1S
The Feather 1S as a solder-down module for your own PCB.
The same board as the Feather 1S with the USB-C, solar and Qwiic connectors left off and their signals brought to the castellations. For product teams who want the charger, BMS, gauge and supervisor as one tested part on their own carrier.
- Every signal on castellations, including USB data and solar input
- Same firmware, same register map, same library as the Feather 1S
- Pre-certified radio module; carry "Contains" labels, not a radio test
- Reel-friendly packaging on request for runs of 100 or more
$49.00 CAD
Bare board, no cell. Pinout card and compliance insert included.
Shipping from $9.95 CAD in Canada, tracked. US orders ship duty prepaid. Also on Tindie. Ten or more? Ask about wholesale.
Specifications
Core 1S, in numbers
Values marked measured come from the characterization report of 14 September 2026.
Battery
| Cells | 1S |
|---|---|
| Chemistries | Li-ion, LiPo, LiHV, LiFePO4, LiSOCl2 primary mode |
| Battery connector | 3-pin JST-PH (BAT, NTC, GND), or the VBAT, NTC and GND castellations |
| Protection | Overcharge, overdischarge, overcurrent, short circuit, temperature; programmable per chemistry |
| Fuel gauge | State of charge, voltage, current, temperature, time to empty; ±3 % on LiFePO4 after one cycle measured |
Inputs
| USB input | VBUS, CC1, CC2, D+ and D− on castellations; 5 V at up to 3 A |
|---|---|
| Solar | 6 to 22 V on castellations, MPPT, 10 W continuous, 15 W peak measured |
| Charge current | 50 mA to 3 A in 10 mA steps; default 0.5 C |
| Charger efficiency | 94 % peak, 91 % at 3 A measured |
Outputs
| 3.3 V rail | 1.5 A continuous measured |
|---|---|
| 5 V rail | 2 A continuous, switchable; off by default measured |
| Signals | PG, CHG_DONE, INT, EN5V, SDA, SCL, VSYS, VBAT on castellations |
Supervisor
| Supervisor | nRF52840 module, Zephyr firmware, I2C at 0x36 |
|---|---|
| Bluetooth LE | BTHome v2 broadcast, Battery Service, custom GATT; no-radio firmware build available |
| Idle current | 28 µA outputs unloaded; 42 µA advertising every 2 s; 3 µA in ship mode measured |
| Libraries | Arduino, C, MicroPython; one register map, v1.2 |
Physical
| Outline | Feather, 50.8 × 22.86 mm, castellated, four mounting holes; 3.1 mm tall with no connectors |
|---|---|
| Board | 4-layer, ENIG, matte navy |
| Operating temperature | −40 to 85 °C board |
Feather header
| Position | Signal | Direction | Note |
|---|---|---|---|
| 3V | 3V3 | out | Regulated 3.3 V; drives the host's 3V position |
| EN | EN (host) | out | Pulled low through a jumper closed by default, so the host's own regulator stays off |
| BAT | — | — | Not connected, by design: the host's charger must never see the battery |
| USB | — | — | Not connected, so two 5 V sources are never in parallel |
| 11 | INT | out, open drain | Event interrupt; jumper open by default |
| A2 | PG | out, open drain | Power good, both rails in regulation; jumper open by default |
| A3 | CHG_DONE | out, open drain | Charge complete; jumper open by default |
| A5 | EN5V | in, pulled up | Enable the 5 V rail; jumper open by default |
| SDA, SCL | I2C | — | Qwiic bus at 3.3 V; the supervisor answers at 0x36 |
| GND | GND | — | |
| off header | 5V | 2-position 3.5 mm screw terminal block and a pad | Rated 2 A; switched by EN5V and set5V() |
| off header | VSYS | Pad and castellation | Raw system rail, battery or input, whichever the power path selects |
| off header | VBAT | Pad and castellation | Battery terminal after the BMS switch; never the host's BAT position |
| off header | NTC | Battery connector pin 2 and a pad | 10 kΩ, B = 3435 by default; other B values are a setting |
The full map, with the host positions each jumper uses and why, is on the pinout page.
The rest of the line
Same pinout, different battery.
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