bryan wade / Mbed 2 deprecated usb_sound_effects

Streams USB audio with sound effects applied. Sound effect selected by joystick and intensity altered by tilting the mbed. Output to the mbed-application-board phono jack.

Dependencies:   C12832_lcd MMA7660 USBDevice mbed

/media/uploads/bw/img_1293.jpg 

/* Uses the mbed LPC1768 and mbed-application-board to create a USB audio device
 * that streams audio from a host computer to headphones or powered speakers. 
 * A couple different sound effects can be applied to the stream in real-time,
 * and tilting the mbed alters intensity of the effect.
 *
 *                                               ECHO
 *       The joystick selects )                   |
 *       one of three effect  )       STRAIGHT -  o  - STRAIGHT
 *       modes.               )                   |
 *                                              REVERB   
 * 
 *
 *
 *                                               \\           ||    
 *       Tilting the mbed     )      ======       \\          ||
 *       determines intensity )                    \\         ||
 *       of the effect.       )
 *                                     0%         50%         100%  
 *
 * The LCD display shows the current effect mode, intesity and buffer level.
*/

delay.cpp

Committer:
bw
Date:
2014-03-27
Revision:
2:9429f84ea165
Parent:
0:bbf6cf0eab95

File content as of revision 2:9429f84ea165:

/*******************************************************************************
 * Implements delay lines for audio samples.
 * Bryan Wade
 * 27 MAR 2014
 ******************************************************************************/
#include "delay.h"
#include "string.h"

struct delay_t { // Implementation of opaque type.
    int16_t *base;
    int16_t *head;
    size_t len;
};

/*
 * Create a delay object given a ptr and size of available RAM.
 * This is only allocating memory for the metadata. The location of 
 * the buffer memory is passed in.
 * @return Ptr to the new delay.
 */
delay_t *Delay_Create(void)
{
    return (delay_t *)malloc(sizeof(delay_t));
}

/*
 * Configure delay buffer location and size.
 * @return True if successful.
 */
bool Delay_Configure(delay_t *delay, void *ram, size_t size)
{
    if (delay) {
        delay->base = delay->head = (int16_t *)ram;
        delay->len = size / sizeof(int16_t);
        memset(ram, 0, size);
        return true;
    }
    
    return false;
}

/*
 * Push a new sample with feedback into the delay while simulateously retieving the output sample.
 * @return Output data.
 */
int16_t Delay_WriteWithFeedback(delay_t *delay, int16_t dataIn, uint16_t gain)
{
    int16_t dataOut = *delay->head;

    // Feedback gain is fixed-point Q16 format.
    *delay->head = dataIn + ((gain * dataOut ) >> 16);
    
    if (++delay->head >= delay->base + delay->len)
        delay->head = delay->base;
        
    return dataOut;
}