Expansion header & fan¶
Expansion header (Exp)¶
The Pro and Max boards, the PocketScroller v3 and the PocketScroller-16 have a 2×6, 2.54 mm pin header
marked Exp. It brings out the cape's I²C bus and eight general-purpose I/O pins,
which FPP names Exp.1 to Exp.8.
Use them for:
- Buttons and switches. In FPP, set up GPIO Inputs to start playlists, run commands or trigger effects. See the FPP manual.
- Outputs to relays (through a driver or relay module), such as a "show running" light.
- I²C accessories such as extra sensors.
The pin positions differ between boards, so check the numbers printed next to the header.
The K8-PB has a different, 24-pin expansion port that drives 16 extra pixel strings through a Falcon F16v4-style expansion board. See its board page.
| Pin | Signal | Pin | Signal |
|---|---|---|---|
| 1 | 3.3 V | 2 | Exp.1 |
| 3 | SDA | 4 | Exp.2 |
| 5 | SCL | 6 | Exp.3 |
| 7 | Exp.4 | 8 | Exp.5 |
| 9 | GND | 10 | Exp.6 |
| 11 | Exp.7 | 12 | Exp.8 |
| Pin | Signal | Pin | Signal |
|---|---|---|---|
| 1 | 3.3 V | 2 | Exp.8 |
| 3 | SDA | 4 | Exp.7 |
| 5 | SCL | 6 | Exp.6 |
| 7 | Exp.4 | 8 | Exp.5 |
| 9 | GND | 10 | Exp.3 |
| 11 | Exp.1 | 12 | Exp.2 |
Electrical limits
The Exp pins come from an I²C I/O expander. They are 3.3 V only, and they pull up weakly and can only sink current. Use them with switches to ground, or to drive a transistor or an opto-isolated relay module. Do not connect 5 V or 12 V signals, and don't drive LEDs or relays directly.
The K16 and K32 have no expansion header.
Fan¶
The Pro and Max boards have a 4-pin 5 V PWM fan header marked Fan 5V. It's the standard PC-fan layout:
| Pin | Signal |
|---|---|
| 1 | GND |
| 2 | +5 V |
| 3 | Tach (speed sense) |
| 4 | PWM (speed control) |
Use a 5 V 4-pin PWM fan. 12 V PC fans won't spin properly. FPP controls the fan from the board temperature sensor:
| Board temperature | Fan speed |
|---|---|
| below 40 °C | off |
| 40 °C | about 30 % |
| 50 °C | about 60 % |
| 60 °C and above | 100 % |
A fan is optional. Most installations don't need one, but it helps in a closed enclosure in direct sun, or with Max boards running many ports near their limit.
Boards from revision v4.1 also read the fan's tach signal, so FPP can monitor the fan's speed. Earlier boards control the fan the same way but can't tell whether it is spinning.