Adafruit Feather (standard footprint)

Fig. 1. Adafruit Feather (standard footprint), 16-pin and 12-pin headers, 0.9 x 2.0 in. Hover or tap a signal to light up every pin that carries it.

• This is the specification, not a particular board. Positions and roles are fixed across the family; which physical port pin sits behind each name is not, so a D10 is a different silicon pin on a Feather M4 than on a Feather RP2040.
• 3.3 V is required by the spec. No Feather may need 5 V logic, which is what lets any Wing stack on any mainboard.
• The digital pins skip: D13, D12, D11, D10, D9, then D6, D5. There is no D7 or D8 on the footprint, and code ported from another board that assumes a contiguous run will not fit.
• Position 16 on the long side is a deliberate free pin. Every board puts something different there, so a Wing must not rely on it.
• BAT is a LiPo rail, not a generic input. The spec obliges every mainboard to include charging and a JST-PH connector, which is why Feathers are the usual choice for a battery project.
• EN pulls down to shut off the 3.3 V regulator, and only that. BAT and USB stay live, so it is a logic-off switch and not a power cut.
• A0 is commonly the DAC output on Feathers that have one, which is worth knowing before using it as a plain analog input.
• The QT Py and Seeed XIAO share a different, smaller 14-pin footprint. Feather Wings do not fit those.

Table 1. Pin assignments.