122 lines
5.5 KiB
Markdown
122 lines
5.5 KiB
Markdown
---
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active: false
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created: 2025-05-03
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tags:
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- eg
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- project
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---
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## Goal
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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.
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![[Pasted image 20240618071431.png]]
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Pin 1 on GPIO connector goes to Pin 1 on the breakout board.
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[Protect digital inputs][1] externally to avoid blowing out RPi's
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## J9
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.png)
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![[Ribbon_Cable_Orientation.png.png]]
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## U1 Chip Output
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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)
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| Socket | Socket Pin | GPIO BCM | GPIO Pin | Action |
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| ------ | ---------- | -------- | -------- | ----------------------------- |
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| RST | 3 | 20 | 38 | RST (0 = disable, 1 = enable) |
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| A | 11 | 17 | 11 | Refer to selector table below |
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| B | 10 | 27 | 13 | -"- |
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| C | 9 | 22 | 15 | -"- |
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### Selector table for U1
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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.
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| Reset | A (GPIO 17) | B (GPIO 27) | C (GPIO 22) |
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| ----- | ----------- | ----------- | ----------- |
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| J1 | 0 | 0 | 0 |
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| J2 | 1 | 0 | 0 |
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| J3 | 0 | 1 | 0 |
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| J4 | 1 | 1 | 0 |
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| J5 | 0 | 0 | 1 |
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| J6 | 1 | 0 | 1 |
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| J7 | 0 | 1 | 1 |
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| J8 | 1 | 1 | 1 |
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## J1 to J8
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.png)
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| Socket | Socket Pin | GPIO BCM | GPIO Pin | Action |
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| ------ | ---------- | -------- | -------- | ------------------------------------- |
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| Jn | 1 | 8 | 24 | SDA/SPI0/CE0 |
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| | 2 | 11 | 23 | SCK |
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| | 3 | 10 | 19 | MOSI |
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| | 4 | 9 | 21 | MISO |
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| | 5 | 4 | 7 | IRQ |
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| | 6 | | 25 | Ground |
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| | 7 | 20 | 38 | RST (See U1 table above for selector) |
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| | 8 | | 17 | 3V3 |
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## J17 to J22
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.png)
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| Socket | Socket Pin | GPIO BCM | GPIO Pin | Action |
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| ------ | ---------- | -------- | -------- | ------ |
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| J22 | 1 | | 9 | Ground |
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| | 2 | 25 | 22 | I/O |
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| J21 | 1 | | 9 | Ground |
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| | 2 | 18 | 12 | I/O |
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| J20 | 1 | | 9 | Ground |
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| | 2 | 23 | 16 | I/O |
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| J19 | 1 | | 9 | Ground |
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| | 2 | 24 | 18 | I/O |
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| J18 | 1 | | 9 | Ground |
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| | 2 | 12 | 32 | I/O |
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| J17 | 1 | | 9 | Ground |
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| | 2 | 16 | 36 | I/O |
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## J10 to J15
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.png)
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| Socket | Socket Pin | GPIO BCM | GPIO Pin | Action |
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| ------ | ---------- | -------- | -------- | ------ |
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| J10 | 1 | 5 | 29 | I/O |
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| | 2 | | 39 | Ground |
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| | 3 | | 1 | 3V3 |
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| J11 | 1 | 6 | 31 | I/O |
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| | 2 | | 39 | Ground |
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| | 3 | | 1 | 3V3 |
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| J12 | 1 | 13 | 33 | I/O |
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| | 2 | | 39 | Ground |
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| | 3 | | 1 | 3V3 |
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| J13 | 1 | 19 | 35 | I/O |
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| | 2 | | 39 | Ground |
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| | 3 | | 1 | 3V3 |
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| J14 | 1 | 26 | 37 | I/O |
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| | 2 | | 39 | Ground |
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| | 3 | | 1 | 3V3 |
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| J15 | 1 | 21 | 40 | I/O |
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| | 2 | | 39 | Ground |
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| | 3 | | 1 | 3V3 |
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## J16
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.png)
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| Socket | Socket Pin | GPIO BCM | GPIO Pin | Action |
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| ------ | ---------- | -------- | -------- | ---------- |
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| J16 | 1 | | 9 | Ground |
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| | 2 | | 1 | 3V3 |
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| | 3 | 3 | 5 | SDL1 / I2C |
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| | 4 | 2 | 3 | SDA1 / I2C |
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## References
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[1]: https://www.digikey.com/en/articles/protecting-inputs-in-digital-electronics |