Control surface
As of version 0.8.0, you can connect buttons and/or a rotary encoder to your Raspberry Pi to control mt32-pi.
Controls are enabled by setting the scheme option in the [control] section of configuration file. Only one of the following schemes may be enabled at a time.
Currently, two "simple" control schemes are implemented. The following schemes will eventually gain additional actions through combinations or long-presses. A menu system and other interactive controls are also planned for future versions.
4 buttons via GPIO:
| Control | Action |
|---|---|
| Button 1 | Switch synthesizer |
| Button 2 | Switch MT-32 ROM or SoundFont |
| Button 3 | Decrease volume |
| Button 4 | Increase volume |
2 buttons and a rotary encoder via GPIO:
| Control | Action |
|---|---|
| Button 1 | Switch synthesizer |
| Button 2 | Switch MT-32 ROM or SoundFont |
| Encoder counter-clockwise | Decrease volume |
| Encoder clockwise | Increase volume |
| Encoder button | Not yet used (shows a test message) |
⚠ Note: Buttons should be connected between the appropriate GPIO pin and
GND. No pull-up resistors are required for the buttons or encoder pins; the Raspberry Pi's internal pull-up resistors are enabled.
The rotary encoder has an additional option, encoder_type. When configured properly, one click of the encoder should increase or decrease the volume by exactly 1.
The default value of full assumes that one detent ("click") performs a full cycle of the Gray code.
- If four clicks are needed for a single movement, try
encoder_type = quarter. - If two clicks are needed for a single movement, try
encoder_type = half.
A typical rotary encoder will have the following pinout. Note that this diagram is for a bare rotary encoder, and not a "breakout board" or "module".
- If your encoder looks different, consult its datasheet.
- If clockwise/counter-clockwise actions are reversed, swap the
CLKandDATpins.
There are various "breakout boards" or "modules" available such as the KY-040 and its clones. These modules often have a " " pin to enable their own pull-up resistors.
If you must use such a module, DO NOT connect the " " pin to 5V on the Raspberry Pi, otherwise you could cause permanent damage to the Pi's GPIOs, which are not 5V tolerant.
Instead, connect it to 3.3V. Alternatively, remove the pullup resistors from the board and leave " " disconnected - mt32-pi enables the Raspberry Pi's own internal pull-up resistors on the encoder pins, so external pullup resistors should not be necessary.
In general, we do not recommend these modules. The encoders themselves tend to be fairly poor quality.
© Dale Whinham 2020-2022. Released under the GNU General Public License v3.0.
