escape_gallery_obsidian_vault/Projects/Electronics/GPIO Breakout Board v3.md

active, created, tags

active	created	tags
false	2025-04-29 08:16	eg project

S## Goal

Create an RPi puzzle breakout board that makes it easier to plug in different switches, RFID readers and I2C components with connector pins holes aligned with red/yellow/black wires on commonly available leads.

!

Pin 1 on GPIO connector goes to Pin 1 on the breakout board.

!

J9

!

U1 Chip Output

We use a CD4051B multiplexer chip to turn 3 GPIO lines (17, 27, 22) into 8 output control lines. The chip's INH (disable pin) is permanently held low. GPIO 20 provides the X input value (high or low depending the use case)

Socket	Socket Pin	BCM	Pin	Action
X	3	20	38	Master enable switch (0 = off, 1 = on)
A	11	17	11	Refer to selector table
B	10	27	13	Refer to selector table
C	9	22	15	Refer to selector table

Selector table U1

Reset	RSTn	A (BCM 17)	B (BCM 27)	C (BCM 22)
J1	0	0	0	0
J2	1	1	0	0
J3	2	0	1	0
J4	3	1	1	0
J5	4	0	0	1
J6	5	1	0	1
J7	6	0	1	1
J8	7	1	1	1

J1 to J8

Socket	Socket Pin	BCM	Pin	Action
Jn	1	8	24	SDA/SPI0/CE0
	2	11	23	SCK
	3	10	19	MOSI
	4	9	21	MISO
	5			Not connected
	6		25	Ground
J2	7			See U1 table
J3	7			See U1 table
J4	7			See U1 table
J5	7			See U1 table
J6	7			See U1 table
J7	7			See U1 table
J8	7			See U1 table
Jn	8		17	3V3

J17 to J22

Socket	Socket Pin	BCM	Pin	Action	Position
J22	1		9	Ground
	2	25	22	I/O
J21	1		9	Ground
	2	18	12	I/O PWM0
J20	1		9	Ground
	2	23	16	I/O
J19	1		9	Ground
	2	24	18	I/O
J18	1		9	Ground
	2	12	32	I/O PWM0
J17	1		9	Ground
	2	16	36	I/O

J10 to J15

Socket	Socket Pin	BCM	Pin	Action
J10	1	5	29	I/O
	2		39	Ground
	3		1	3V3
J11	1	6	31	I/O
	2		39	Ground
	3		1	3V3
J12	1	13	33	I/O PWM1
	2		39	Ground
	3		1	3V3
J13	1	19	35	I/O PWM1
	2		39	Ground
	3		1	3V3
J14	1	26	37	I/O
	2		39	Ground
	3		1	3V3
J15	1	21	40	I/O
	2		39	Ground
	3		1	3V3

J16

Socket	Socket Pin	BCM	Pin	Action	Wire Color
J16	1		9	Ground	Black
	2		1	3V3	Red
	3	3	5	SCL1 / I2C	White
	4	2	3	SDA1 / I2C	Yellow