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BTN-1 GPIO pinout

The BTN-1 has two GPIO headers on its circuit board: a 10-pin header on the side and a 16-pin header on the top. Use these maps to wire extra sensors, LEDs, or other hardware to your BTN-1 and to find the GPIO numbers you need in ESPHome.

Open the case to reach the headers

The headers are on the circuit board inside the case. Follow Teardown and reassembly of BTN-1 to lift out the board, and flip the battery switch off first if your BTN-1 has a battery.

Side header

BTN-1 side GPIO header seen edge-on, with pins 1 to 5 on the top row, pins 6 to 10 on the bottom row, and the function of each pin listed below

The table below is laid out like the header in the photo, with pin 1 at the end farthest from the USB-C port.

Row
Nearest the board 1 GPIO23 2 Ground 3 LED_Next (GPIO21) 4 +VOUTPUT 5 +3v3_CTRL
Outer 6 GPIO4 7 GPIO22 8 GPIO19 9 SCL 10 SDA
  • LED_Next is tied to the BTN-1's existing LEDs.
  • +VOUTPUT is 5V from USB, or + from the battery.

Top header

BTN-1 top GPIO headers on the circuit board, with pins 1 to 8 on the left header, pins 9 to 16 on the right header, and the function of each pin listed below

The top header is two blocks of eight pins, laid out below like the header in the image.

Block nearest the USB-C port

Row
Nearest the board 1 +VBAT 2 Reset button 3 Boot button (GPIO2) 4 SCL (GPIO0)
Outer 5 USB D- 6 USB D+ 7 SDA (GPIO1) 8 GPIO3

Block nearest the buttons

Row
Nearest the board 9 GPIO7 10 GPIO14 11 GPIO15 12 GPIO20
Outer 13 +5V 14 +3v3_CTRL 15 GPIO22 16 Ground

+3v3_CTRL is switched

The +3v3_CTRL pin on both headers only has power while GPIO18 is on. If something you power from it stays off, check that GPIO18 is on.