Sending relative MIDI Events on Rotary Encoder movements

We want to send relative CC events on encoder movements in following format: CC <encoder> <+/- speed>.

Copy the SDCC skeleton into a new directory, open the main.c file and enhance the hooks like described below. Thereafter type "make" in the command shell, and upload the new project.hex file to the core.

Within the Init() function, you have to specify, how many shift registers are connected to the core, and which encoder speed mode should be taken:

/////////////////////////////////////////////////////////////////////////////
// This function is called by MIOS after startup to initialize the 
// application
/////////////////////////////////////////////////////////////////////////////
void Init(void) __wparam
{
  unsigned char i;

  // set shift register update frequency
  MIOS_SRIO_UpdateFrqSet(1); // ms

  // we need to set at least one IO shift register pair
  MIOS_SRIO_NumberSet(16); // for 128 pins

  // set speed mode for 8 encoders
  for(i=0; i<8; ++i) {
    // available speed modes: SLOW, NORMAL and FAST
    MIOS_ENC_SpeedSet(i, MIOS_ENC_SPEED_FAST, 2); // encoder, speed mode, divider
  }
}

We add the code which should be executed on rotary encoder movements to the ENC_NotifyChange() function:

/////////////////////////////////////////////////////////////////////////////
// This function is called by MIOS when an encoder has been moved
// incrementer is positive when encoder has been turned clockwise, else
// it is negative
/////////////////////////////////////////////////////////////////////////////
void ENC_NotifyChange(unsigned char encoder, char incrementer) __wparam
{
  MIOS_MIDI_TxBufferPut(0xb0);           // CC at MIDI Channel #1
  MIOS_MIDI_TxBufferPut(0x10 + encoder); // CC# is 0x10 (16) for first encoder
  MIOS_MIDI_TxBufferPut((0x40 + incrementer) & 0x7f);
  // this "40 +/- speed" format is used by NI software and some others
}

The pins to which the encoders are connected must be specified in MIOS_ENC_TABLE, which can be placed at the top of your main.c file:

MIOS_ENC_TABLE {
             //  sr pin mode
  MIOS_ENC_ENTRY( 1, 0, MIOS_ENC_MODE_NON_DETENTED), // V-Pot 1
  MIOS_ENC_ENTRY( 1, 2, MIOS_ENC_MODE_NON_DETENTED), // V-Pot 2
  MIOS_ENC_ENTRY( 1, 4, MIOS_ENC_MODE_NON_DETENTED), // V-Pot 3
  MIOS_ENC_ENTRY( 1, 6, MIOS_ENC_MODE_NON_DETENTED), // V-Pot 4
  MIOS_ENC_ENTRY( 2, 0, MIOS_ENC_MODE_NON_DETENTED), // V-Pot 5
  MIOS_ENC_ENTRY( 2, 2, MIOS_ENC_MODE_NON_DETENTED), // V-Pot 6
  MIOS_ENC_ENTRY( 2, 4, MIOS_ENC_MODE_NON_DETENTED), // V-Pot 7
  MIOS_ENC_ENTRY( 2, 6, MIOS_ENC_MODE_NON_DETENTED), // V-Pot 8

  MIOS_ENC_EOT
};

IMPORTANT: the default encoder table has to be disabled in the Makefile via -DDONT_INCLUDE_MIOS_ENC_TABLE. You could add this define to the MIOS_WRAPPER_DEFINES variable:

MIOS_WRAPPER_DEFINES = -DSTACK_HEAD=0x37f -DSTACK_IRQ_HEAD=0x33f -DDONT_INCLUDE_MIOS_ENC_TABLE

A list of available MIOS function can be found here.



Last update: 2018-05-10

Copyright 1998-2018, Thorsten Klose. All rights reserved.