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Projects/Electronics/GPIO Breakout Board v4.md Normal file
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---
active: false
created: 2025-05-03
tags:
- 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.
![[Pasted image 20240618071431.png]]
Pin 1 on GPIO connector goes to Pin 1 on the breakout board.
[Protect digital inputs][1] externally to avoid blowing out RPi's
## J9
![Image.png](Attachments/Puzzle%20Breakout%20Board.assets/Image%20(3).png)
![[Ribbon_Cable_Orientation.png.png]]
## U1 Chip Output
We use a [CD4051B](https://www.ti.com/lit/ds/symlink/cd4051b.pdf) 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)
![Image.png](Attachments/Puzzle%20Breakout%20Board.assets/Image.png)
| 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
![Image.png](Attachments/Puzzle%20Breakout%20Board.assets/Image%20(2).png)
| 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
![Image.png](Attachments/Puzzle%20Breakout%20Board.assets/Image%20(6).png)
| 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
![Image.png](Attachments/Puzzle%20Breakout%20Board.assets/Image%20(4).png)
| 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
![Image.png](Attachments/Puzzle%20Breakout%20Board.assets/Image%20(5).png)
| 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
[1]: https://www.digikey.com/en/articles/protecting-inputs-in-digital-electronics