56 lines
2.6 KiB
Markdown
56 lines
2.6 KiB
Markdown
# MIDI Footswitch
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AVR-based footswitch controller for MIDI appliances.
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The current implementation supports 4 pushbuttons and 1 toggle switch (usually bank switcher) and a hard-coded range of MIDI sequences.
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Hardware i s based on a single ATtiny2313 microprocessor.
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Original design intended to retrofit an analog _Vox VFS5_ footswitch to control an _Axe-Fx II_ effect processor by _Fractal Audio Systems_.
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However the housing might be custom made as well or fit into any other pushbutton-based device.
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## Hardware Specs
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Hardware is designed to work with a power supply of 7 to 25V DC which is suitable for a standard 9V DC power supply or battery which is common for effect pedals.
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The logic is powered by a Atmel/Microchip ATtiny2313 processor, which can be swapped with about any AVR controller providing 8 I/O ports and a USART interface.
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MIDI signal is directly connected to the USART output (active low) of the controller and the 5V DC supply of the board through two 220 Ohm resistors.
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| Pin on Controller | Pin on MIDI Jack | Function |
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|:-----------------:|:----------------:|:----------------------:|
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| X5.1 | 2 | Ground |
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| X5.2 | 5 | Signal through 220 Ohm |
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| X5.3 | 4 | +5V through 220 Ohm |
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The provided layout is perfboard compatible with a more or less minimal layout to fit into the footswitch casing without removing the original PCB.
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## Footswitch Layout and transmitted MIDI codes
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| Label | BANK | CH1 | CH2 | CH3 | CH4 (Tuner) |
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|:--------------:|:-------------------:|:---:|:---:|:---:|:-----------:|
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| **LED** | ⭕ (1 green, 2 red) | - | - | - | - |
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| **Button** | ⭗ | ⭗ | ⭗ | ⭗ | ⭗ |
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| **MIDI Codes** | Bank 1: 0xB0 0x00 0x00 0xC0 0x00<br>Bank 2: 0xB0 0x00 0x01 0xC0 0x00 | 0xC0 0x00 | 0xC0 0x01 | 0xC0 0x02 | 0xB0 0x0F 0x7F |
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As documented, the _CH4_ Button does not enable Channel 4 as expected, but sets the effect processor into tuner mode (which bypasses the output, so implicit mute).
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Thus you effectively control 3 channels on each bank 1 and bank 2.
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The LED is green for Bank 1 and red for Bank 2. When in tuner mode the LED flashes in the current color with a frequency of about 2 Hz.
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## Final Example
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Below two pictures of the final prototype implementation handsoldered on a perfboard.
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Placed inside a _VFS5_ next to the original parts.
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## License
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The project is licensed under [GPL v3](https://www.gnu.org/licenses/gpl-3.0.de.html) license.
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