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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.

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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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36
Projects/Incomplete/MIDIToneGenerator/MIDIToneGenerator.h
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@ -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);