Digital Index Operator

Idea by Scott Shawcroft (@tannewt).

3D printed clips that hold two pogo pins on a board's RESET or BOOT button, so a test rig can press it with a relay.

George Jetson's job at Spacely Sprockets was digital index operator: he pressed one button all day. These clips do the same for hardware-in-the-loop testing.

How it works

Cutaway of the clip seated on a tact switch, pogo pins touching opposite corner pads — Cutaway of the clip on the switch. Each glow color marks one pair of pads that are tied together inside the switch. Click for the video.

The clip registers on the switch body and holds two pogo pins on opposite corner pads. The two pads on each side of a tact switch are tied together inside, so diagonal corners are the two sides of the switch.
A window over the plunger means the clip itself never presses the button.
Print bore_coupon.3mf first and set bore_d to the hole that grips a pin snugly. Push the pins in from below.

Edge clamp

Hole mount

Files

3MF files ready to print, one per board button and one per switch type. Start with 3mf/fitted/ and 3mf/bore_coupon.3mf.
FreeCAD files (FreeCAD 1.1). Both designs are parametric: pick a board row or switch type in the Params sheet, or type your own edge distance or hole position, and the clip regenerates. Fit values such as bore size and clearance live there too.

Parts from Adafruit

Part	Why
Pogo Pins "Needle Head" P75-B1 (2430)	The contact. 1.0 mm body, 0.7 mm tip, small enough to land on the pads of a 4.2 mm tact switch. Two per clip.
Pogo Pins "Crown Head" P75-H2 (2429)	Optional. Better grip on the larger 6 mm switch pads used on Metros.
M2.5 Nylon Screw and Stand-off Set (3299)	Hole mount on Feathers: M2.5 x 10 screw and nut.
M3 Nylon Screw and Stand-off Set (4685)	Hole mount on Metros: M3 x 10 screw and nut.
Silicone Cover Stranded Wire 30AWG (2051)	Solder to the pogo pin tails.
STEMMA Non-Latching Mini Relay (4409)	Closes the two wires to press the button from any microcontroller.
Pre-Cut Heat Shrink Pack (4559)	Insulate the solder joints.
Feather RP2040 (4884)	The board shown in the videos.

Button reference

Distance from each button center to the nearest board edge and mounting hole, from the Adafruit Eagle files. "Row" is the board number in the FreeCAD Params sheet.

Board	Button	Ref	Switch	Side	Nearest edge	Nearest hole	Row
Feather RP2040 rev D	RESET	SW1	KMR2	top	6.41 mm (bottom)	10.1 mm (M2.5)	1
Feather RP2040 rev D	BOOT	SW3	RA_MINI	top	1.65 mm (right)	5.1 mm (M2.5)	2
ESP32-S3 TFT Feather Rev D	RESET	SW2	RKB2	bottom	6.22 mm (bottom)	7.5 mm (M2.5)	3
ESP32-S3 TFT Feather Rev D	BOOT	SW1	RKB2	bottom	6.22 mm (bottom)	11.8 mm (M2.5)	4
Adafruit Feather nRF52840 Rev E	RESET	SW1	RKB2	top	6.22 mm (bottom)	37.3 mm (M2.5)	5
Adafruit Feather nRF52840 Rev E	USER	SW2	RKB2	top	6.17 mm (bottom)	18.7 mm (M2.5)	6
Feather M4 AirLift rev A	RESET	SW1	KMR2	top	6.54 mm (bottom)	7.9 mm (M2.5)	7
ItsyBitsy M4 rev D	RESET	SW1	RKB2	top	5.22 mm (right)	none	8
ItsyBitsy RP2040 rev C1	RESET	SW2	KMR2	top	4.95 mm (bottom)	none	9
ItsyBitsy RP2040 rev C1	BOOT	SW3	KMR2	top	4.95 mm (top)	none	10
QT Py RP2040 rev B	BOOT	SW2	RKB2	top	5.16 mm (left)	none	11
QT Py RP2040 rev B	RESET	SW1	RKB2	top	2.79 mm (bottom)	none	12
QT Py ESP32-S3 rev C	RESET	RESET	RKB2	top	6.10 mm (left)	none	13
QT Py ESP32-S3 rev C	BOOT	BOOT	RKB2	top	6.10 mm (left)	none	14
Metro ESP32-S3 rev B	RESET	SW3	RA_METRO	top	1.71 mm (top)	14.0 mm (M3)	15
Metro ESP32-S3 rev B	BOOT	SW1	RKB2	top	14.48 mm (right)	26.2 mm (M3)	16
Metro M4 AirLift rev B1	RESET	RESET	6x6_SMT	top	3.81 mm (top)	9.0 mm (M3)	17
Metro Express rev H	RESET	RESET	6x6_SMT	top	3.94 mm (top)	9.0 mm (M3)	18
Metro Amethyst rev D	RESET	SW2	RA_METRO	top	1.78 mm (left)	13.9 mm (M3)	19
Metro Amethyst rev D	BOOT	SW3	RA_METRO	top	4.32 mm (right)	7.8 mm (M3)	20