GPIO Pinouts
The Acorn Tube interface comprises the following 15 signals:
- D[7:0]
- A[2:0]
- nRST
- nTUBE
- RnW
- Phi2 (aka 2MhzE)
Note, A[6:3] and nIRQ are left unconnected on virtually all Co Processors.
Our goals when assigning a GPIO pinout were to:
- support older Pi's with a 26-pin GPIO header
- support newer Pi's with a 40-pin GPIO header
- allow the same physical level shifter to be used for both
- map the data bus onto consecutive GPIO pins (so formatting the data is more efficient)
| Name | Tube Pin | Wire Colour | GPIO Pin | GPIO Pin Name |
|---|---|---|---|---|
| White | Pin 1 | 3V3 | ||
| Pin 2 | 5V | |||
| A1 | Pin 30 | Blue | Pin 3 | GPIO0 (GPIO2 on later models) |
| Pin 4 | 5V | |||
| A2 | Pin 32 | Green | Pin 5 | GPIO1 (GPIO3 on later models) |
| Pin 6 | Serial GND | |||
| nRST | Pin 10 | Blue | Pin 7 | GPIO4 |
| Pin 8 | Serial Tx | |||
| Pin 9 | GND | |||
| Pin 10 | Serial Rx | |||
| nTUBE | Pin 8 | Purple | Pin 11 | GPIO17 |
| RnW | Pin 2 | White | Pin 12 | GPIO18 |
| A0 | Pin 28 | Purple | Pin 13 | GPIO21 (GPIO27 on later models) |
| Pin 14 | GND | |||
| D4 | Pin 20 | Brown | Pin 15 | GPIO22 |
| D5 | Pin 22 | Black | Pin 16 | GPIO23 |
| Pin 17 | 3V3 | |||
| D6 | Pin 24 | White | Pin 18 | GPIO24 |
| D2 | Pin 16 | Orange | Pin 19 | GPIO10 |
| Pin 20 | GND | |||
| D1 | Pin 14 | Yellow | Pin 21 | GPIO9 |
| D7 | Pin 26 | Grey | Pin 22 | GPIO25 |
| D3 | Pin 18 | Red | Pin 23 | GPIO11 |
| D0 | Pin 12 | Green | Pin 24 | GPIO8 |
| GND | Pin 1 | Black | Pin 25 | GND |
| Phi2 | Pin 4 | Grey | Pin 26 | GPIO7 |
| nIRQ | Pin 6 | not connected | ||
| A3 | Pin 34 | not connected | ||
| A4 | Pin 36 | not connected | ||
| A5 | Pin 38 | not connected | ||
| A6 | Pin 40 | not connected |
| Name | Tube Pin | Wire Colour | GPIO Pin | GPIO Pin Name |
|---|---|---|---|---|
| GND | Pin 1 | Black | Pin 25 | GND |
| RnW | Pin 2 | White | Pin 12 | GPIO18 |
| Phi2 | Pin 4 | Grey | Pin 26 | GPIO7 |
| nIRQ | Pin 6 | not connected | ||
| nTUBE | Pin 8 | Purple | Pin 11 | GPIO17 |
| nRST | Pin 10 | Blue | Pin 7 | GPIO4 |
| D0 | Pin 12 | Green | Pin 24 | GPIO8 |
| D1 | Pin 14 | Yellow | Pin 21 | GPIO9 |
| D2 | Pin 16 | Orange | Pin 19 | GPIO10 |
| D3 | Pin 18 | Red | Pin 23 | GPIO11 |
| D4 | Pin 20 | Brown | Pin 15 | GPIO22 |
| D5 | Pin 22 | Black | Pin 16 | GPIO23 |
| D6 | Pin 24 | White | Pin 18 | GPIO24 |
| D7 | Pin 26 | Grey | Pin 22 | GPIO25 |
| A0 | Pin 28 | Purple | Pin 13 | GPIO21 (GPIO27 on later models) |
| A1 | Pin 30 | Blue | Pin 3 | GPIO0 (GPIO2 on later models) |
| A2 | Pin 32 | Green | Pin 5 | GPIO1 (GPIO3 on later models) |
| A3 | Pin 34 | not connected | ||
| A4 | Pin 36 | not connected | ||
| A5 | Pin 38 | not connected | ||
| A6 | Pin 40 | not connected | ||
| White | Pin 1 | 3V3 | ||
| Pin 2 | 5V | |||
| Pin 4 | 5V | |||
| Pin 6 | Serial GND | |||
| Pin 8 | Serial Tx | |||
| Pin 9 | GND | |||
| Pin 10 | Serial Rx | |||
| Pin 14 | GND | |||
| Pin 17 | 3V3 | |||
| Pin 20 | GND |
For reference, here's the different GPIO pinouts of the different Pi Models:
[Source] (http://raspi.tv/2014/rpi-gpio-quick-reference-updated-for-raspberry-pi-b)
TODO: Expand this section
Depending on the construction of these level shifter, it may be possible to use more GND pins:
- Tube GND pins: 1, 3, 5, 7, 9, 11, 13, 15, 17, 19, 21, 23, 25, 27, 29
We still need to resolve whether it's possibly to reliably power the Pi from the Tube connector +5V supply
- Tube 5V pins: 31, 33, 35, 37, 39