main.cpp

00001 // Hello World example for the USBMIDI library
00002 
00003 #include "mbed.h"
00004 #include "USBMIDI.h"
00005 
00006 void show_message(MIDIMessage msg) {
00007     switch (msg.type()) {
00008         case MIDIMessage::NoteOnType:
00009             printf("NoteOn key:%d, velocity: %d, channel: %d\n", msg.key(), msg.velocity(), msg.channel());
00010             break;
00011         case MIDIMessage::NoteOffType:
00012             printf("NoteOff key:%d, velocity: %d, channel: %d\n", msg.key(), msg.velocity(), msg.channel());
00013             break;
00014         case MIDIMessage::ControlChangeType:    
00015             printf("ControlChange controller: %d, data: %d\n", msg.controller(), msg.value());
00016             break;
00017         case MIDIMessage::PitchWheelType:
00018             printf("PitchWheel channel: %d, pitch: %d\n", msg.channel(), msg.pitch());
00019             break;
00020         default:
00021             printf("Another message\n");
00022     }    
00023 }
00024 
00025 static const int MIDI_MAX_VALUE = 16384;
00026 static const float MIDI_MAX_VALUE_F = 16384.0f;
00027 
00028 
00029 static const float TOLERANCE = 0.01f;
00030 static const int NOISE_FLOOR = 600;
00031 
00032 static const float LOWER_TOLERANCE = 0.016f;
00033 static const float LOWER_TOLERANCE_BEGIN = 0.34f;
00034 
00035 USBMIDI midi;
00036 AnalogIn pot1(p20);
00037 Serial pc(USBTX, USBRX); // tx, rx
00038 
00039 void write_full_cc(int controlmsb, int controllsb, int channel, int value){
00040     int lsb = value / 128; //value & 0x7F;
00041     int msb = value % 128; //value & 0x7F80 >> 7;
00042     midi.write(MIDIMessage::ControlChange(controlmsb, msb, channel));
00043     midi.write(MIDIMessage::ControlChange(controllsb, lsb, channel));
00044 }
00045 
00046 #define SMOOTHING_AMOUNT 500
00047 
00048 int main() {       
00049     midi.attach(show_message);         // call back for messages received    
00050     
00051     float last_value  = 0.0f;
00052     while (1) {   
00053         float counter=0.0f;
00054         for(int i=0;i<SMOOTHING_AMOUNT;i++){
00055             wait_us(10);
00056             counter+=pot1;
00057         }
00058         float value = counter / SMOOTHING_AMOUNT;
00059         int midi_value = (int)(MIDI_MAX_VALUE_F * value);
00060         
00061         //at low voltage noise takes over..
00062         if(midi_value < NOISE_FLOOR){
00063             value = 0.0f;
00064             midi_value = 0;
00065         }
00066         if(value - last_value > TOLERANCE || value - last_value < -TOLERANCE){
00067             //as we approach noise floor, things get noisey.. 
00068             if(value < LOWER_TOLERANCE_BEGIN && !(value - last_value > LOWER_TOLERANCE || value - last_value < -LOWER_TOLERANCE)){
00069                 continue;
00070             }
00071             pc.printf("sent: %f, %i\r\n", value, midi_value);
00072             last_value = value;
00073             write_full_cc(20, 52, 0, midi_value);
00074        }
00075         
00076     }
00077 }