Control Surface
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MIDI Control Surface library for Arduino
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This example demonstrates the use of MCP23017 IĀ²C port expanders with rotary encoders that send relative Control Change messages.
Connect up to 8 encoders to the MCP23017's GPIO pins: the first encoder connects to GPIO A0 and A1, the second encoder connects to GPIO A2 and A3, ..., the eighth encoder connects to GPIO B6 and B7.
Connect the "common" pins of the encoders to ground.
The built-in pull-up resistors of the MCP23017 will be enabled.
Make sure that the reset and address pins are all configured correctly (reset to Vcc; A0, A1 and A2 to ground).
If you need more than one MCP23017 with encoders, you can connect their interrupt pins together. This does result in higher latency, because on average, half of the total number of MCP23017s have to be polled, which is relatively slow, and might lead to missed pulses when using a large number of encoders.
When the position of one of the encoders changes, a relative Control Change message is sent.
Map the Arduino as a Mackie Control Universal in your DAW. The encoders will control the pan (just like the V-Pots on an MCU).
The interrupt pin of the MCP23017 doesn't trigger a hardware interrupt on the Arduino. It's used only to determine whether the Arduino should read the GPIO registers from the MCP23017.
If the update function isn't called often enough, you will miss encoder pulses, and the position will be incorrect.
It's very important to keep your main loop free from any code that blocks for more than a couple of hundreds of microseconds.
Keep in mind that reading analog inputs can be slow, so adding lots of potentiometers to Control Surface will interfere with the encoders.
Written by PieterP, 2020-04-06
https://github.com/tttapa/Arduino-Helpers