MCP23017-RotaryEncoder-No-Interrupts.ino

MCP23017-RotaryEncoder-No-Interrupts

This example demonstrates the use of MCP23017 I²C port expanders with rotary encoders that send relative Control Change messages.

Boards: 🛈

AVR, AVR USB, Nano Every, Nano 33 IoT, Nano 33 BLE, UNO R4, Pi Pico, Due, Teensy 3.x, ESP8266, ESP32

Connections

• SDA: MCP23017 SDA
• SCL: MCP23017 SCL
• 12: MCP23017 INTA or INTB

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.

Behavior

When the position of one of the encoders changes, a relative Control Change message is sent.

Mapping

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).

Cautions

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

 
#include <Wire.h>
 
#include <Control_Surface.h>
 
#include <AH/Hardware/MCP23017Encoders.hpp>
 
// Type for the MCP23017 encoders (translates encoder pulses to position)
using WireType = decltype(Wire);     // The type of I²C driver to use
using EncoderPositionType = uint8_t; // The type for saving encoder positions
using MCPEncoderType = MCP23017Encoders<WireType, EncoderPositionType>;
 
// Type for the MIDI encoders (translates position to MIDI messages)
struct CCMCPEncoder : GenericMIDIRotaryEncoder<MCPEncoderType::MCP23017Encoder,
                                               RelativeCCSender> {
  CCMCPEncoder(MCPEncoderType::MCP23017Encoder enc, MIDIAddress address,
               int16_t multiplier = 1, uint8_t pulsesPerStep = 4)
    : GenericMIDIRotaryEncoder(std::move(enc), address, multiplier,
                               pulsesPerStep, {}) {}
};
 
USBDebugMIDI_Interface midi;
 
// Create an object that manages the 8 encoders connected to the MCP23017.
MCPEncoderType enc {Wire, 0x0, 12};
//                  │     │    └─ Interrupt pin
//                  │     └────── Address offset
//                  └──────────── I²C interface
 
// Instantiate 8 MIDI rotary encoders.
CCMCPEncoder ccencoders[] {
  {
    enc[0],       // The encoder to use
    MCU::V_POT_1, // The MIDI address
    1,            // Encoder speed multiplier
    4,            // Number of pulses per physical "click" of the encoder
  },
  {enc[1], MCU::V_POT_2},
  {enc[2], MCU::V_POT_3},
  {enc[3], MCU::V_POT_4},
  {enc[4], MCU::V_POT_5},
  {enc[5], MCU::V_POT_6},
  {enc[6], MCU::V_POT_7},
  {enc[7], MCU::V_POT_8},
};
 
void setup() {
  Control_Surface.begin();
  Wire.begin(); // Must be called before enc.begin()
  Wire.setClock(800000);
  enc.begin(); // Initialize the MCP23017
}
 
void loop() {
  enc.update();
  Control_Surface.loop();
}