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Make the incomplete MIDIToneGenerator project work with up to three notes, using a LRU (Least Recently Used) algorithm to discard the oldest set note when the note table becomes full.

This commit is contained in:
Dean Camera 2010-11-25 02:46:35 +00:00
parent 857a82674f
commit fd77bf5c94
2 changed files with 61 additions and 27 deletions
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52
Projects/Incomplete/MIDIToneGenerator/MIDIToneGenerator.c
View File

@ -78,14 +78,7 @@ const uint8_t SineTable[256] =
};
/** Array of structures describing each note being generated */
struct
{
uint8_t Pitch;
uint32_t TableIncrement;
uint32_t TablePosition;
} NoteData[3];
uint8_t PhaseCounter;
DDSNoteData NoteData[MAX_SIMULTANEOUS_NOTES];
/** Main program entry point. This routine contains the overall program flow, including initial
* setup of all components and the main program loop.
@ -104,19 +97,34 @@ int main(void)
{
if ((ReceivedMIDIEvent.Command == (MIDI_COMMAND_NOTE_ON >> 4)) && ((ReceivedMIDIEvent.Data1 & 0x0F) == 0))
{
DDSNoteData* LRUNoteStruct = &NoteData[0];
/* Find a free entry in the note table to use for the note being turned on */
for (uint8_t i = 0; i < MAX_SIMULTANEOUS_NOTES; i++)
{
/* Check if the note is unused */
if (!(NoteData[i].Pitch))
{
NoteData[i].Pitch = ReceivedMIDIEvent.Data2;
NoteData[i].TableIncrement = (uint32_t)(BASE_INCREMENT * SCALE_FACTOR) +
((uint32_t)(BASE_INCREMENT * NOTE_OCTIVE_RATIO * SCALE_FACTOR) *
(ReceivedMIDIEvent.Data2 - BASE_PITCH_INDEX));
NoteData[i].TablePosition = 0;
/* If a note is unused, it's age is essentially infinite - always prefer unused not entries */
LRUNoteStruct = &NoteData[i];
break;
}
else if (NoteData[i].LRUAge > LRUNoteStruct->LRUAge)
{
/* If an older entry that the current entry has been found, prefer overwriting that one */
LRUNoteStruct = &NoteData[i];
}
NoteData[i].LRUAge++;
}
/* Update the oldest note entry with the new note data and reset its age */
LRUNoteStruct->Pitch = ReceivedMIDIEvent.Data2;
LRUNoteStruct->TableIncrement = (uint32_t)(BASE_INCREMENT * SCALE_FACTOR) +
((uint32_t)(BASE_INCREMENT * NOTE_OCTIVE_RATIO * SCALE_FACTOR) *
(ReceivedMIDIEvent.Data2 - BASE_PITCH_INDEX));
LRUNoteStruct->TablePosition = 0;
LRUNoteStruct->LRUAge = 0;
/* Turn on indicator LED to indicate note generation activity */
LEDs_SetAllLEDs(LEDS_LED1);
@ -129,11 +137,9 @@ int main(void)
for (uint8_t i = 0; i < MAX_SIMULTANEOUS_NOTES; i++)
{
if (NoteData[i].Pitch == ReceivedMIDIEvent.Data2)
{
NoteData[i].Pitch = 0;
FoundActiveNote = true;
break;
}
NoteData[i].Pitch = 0;
else if (NoteData[i].Pitch)
FoundActiveNote = true;
}
/* If all notes off, turn off the indicator LED */
@ -182,15 +188,15 @@ void SetupHardware(void)
/* Sample reload timer initialization */
TIMSK0 = (1 << OCIE0A);
OCR0A = 255;
OCR0A = (VIRTUAL_SAMPLE_TABLE_SIZE / 8);
TCCR0A = (1 << WGM01); // CTC mode
TCCR0B = (1 << CS00); // Fcpu speed
TCCR0B = (1 << CS01); // Fcpu/8 speed
/* Set speaker as output */
DDRC |= (1 << 6);
/* PWM speaker timer initialization */
TCCR3A = ((1 << WGM30) | (1 << COM3A1) | (1 << COM3A0)); // Set on match, clear on TOP
TCCR3A = ((1 << WGM31) | (1 << COM3A1) | (1 << COM3A0)); // Set on match, clear on TOP
TCCR3B = ((1 << WGM32) | (1 << CS30)); // Fast 8-Bit PWM, Fcpu speed
}
@ -208,6 +214,10 @@ void EVENT_USB_Device_Disconnect(void)
{
LEDs_SetAllLEDs(LEDMASK_USB_NOTREADY);
/* Disable any notes currently being played */
for (uint8_t i = 0; i < MAX_SIMULTANEOUS_NOTES; i++)
NoteData[i].Pitch = 0;
/* Set speaker as input to reduce current draw */
DDRC &= ~(1 << 6);
}

36
Projects/Incomplete/MIDIToneGenerator/MIDIToneGenerator.h
View File

@ -65,14 +65,38 @@
/** LED mask for the library LED driver, to indicate that an error has occurred in the USB interface. */
#define LEDMASK_USB_ERROR (LEDS_LED1 | LEDS_LED3)
#define SCALE_FACTOR 65536
#define BASE_FREQUENCY 27.5
#define NOTE_OCTIVE_RATIO 1.05946
#define BASE_PITCH_INDEX 21
#define MAX_SIMULTANEOUS_NOTES 3
/** Scale factor used to convert the floating point frequencies and ratios into a fixed point number */
#define SCALE_FACTOR 65536
#define BASE_INCREMENT (((F_CPU / 255 / 2) / BASE_FREQUENCY))
/** Base (lowest) allowable MIDI note frequency */
#define BASE_FREQUENCY 27.5
/** Ratio between each note in an octave */
#define NOTE_OCTIVE_RATIO 1.05946
/** Lowest valid MIDI pitch index */
#define BASE_PITCH_INDEX 21
/** Maximum number of MIDI notes that can be played simultaneously */
#define MAX_SIMULTANEOUS_NOTES 3
/** Number of samples in the virtual sample table (can be expanded to lower maximum frequency, but allow for
* more simultaneous notes due to the reduced amount of processing time needed when the samples are spaced out)
*/
#define VIRTUAL_SAMPLE_TABLE_SIZE 512
/** Sample table increments per period for the base MIDI note frequency */
#define BASE_INCREMENT (((F_CPU / VIRTUAL_SAMPLE_TABLE_SIZE / 2) / BASE_FREQUENCY))
/* Type Defines: */
typedef struct
{
uint8_t LRUAge;
uint8_t Pitch;
uint32_t TableIncrement;
uint32_t TablePosition;
} DDSNoteData;
/* Function Prototypes: */
void SetupHardware(void);