escape_gallery_obsidian_vault/Projects/Electronics/GPIO Breakout Board v4.md

active, created, tags

active	created	tags
false	2025-05-03	eg project

Goal

Create an RPi puzzle breakout board that makes it easier to plug in different switches, RFID readers and I2C components. Must allow IRQ to be used on SPI interfaces.

!

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

Protect digital inputs externally to avoid blowing out RPi's

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	GPIO BCM	GPIO Pin	Action
RST	3	20	38	RST (0 = disable, 1 = enable)
A	11	17	11	Refer to selector table below
B	10	27	13	-"-
C	9	22	15	-"-

Selector table for U1

RST pins are pulled low to disable the reader. Use address pins A, B, C to target J1 thru J8 with RST on GPIO20 and pull it high to restart the reader.

Reset	A (GPIO 17)	B (GPIO 27)	C (GPIO 22)
J1	0	0	0
J2	1	0	0
J3	0	1	0
J4	1	1	0
J5	0	0	1
J6	1	0	1
J7	0	1	1
J8	1	1	1

J1 to J8

Socket	Socket Pin	GPIO BCM	GPIO Pin	Action
Jn	1	8	24	SDA/SPI0/CE0
	2	11	23	SCK
	3	10	19	MOSI
	4	9	21	MISO
	5	4	7	IRQ
	6		25	Ground
	7	20	38	RST (See U1 table above for selector)
	8		17	3V3

J17 to J22

Socket	Socket Pin	GPIO BCM	GPIO Pin	Action
J22	1		9	Ground
	2	25	22	I/O
J21	1		9	Ground
	2	18	12	I/O
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
J17	1		9	Ground
	2	16	36	I/O

J10 to J15

Socket	Socket Pin	GPIO BCM	GPIO 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
	2		39	Ground
	3		1	3V3
J13	1	19	35	I/O
	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	GPIO BCM	GPIO Pin	Action
J16	1		9	Ground
	2		1	3V3
	3	3	5	SDL1 / I2C
	4	2	3	SDA1 / I2C

References