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.
*/

buffer.cpp@2:9429f84ea165, 2014-03-27 (annotated)

Committer:
bw
Date:
Thu Mar 27 21:43:41 2014 +0000
Revision:
2:9429f84ea165
Parent:
0:bbf6cf0eab95 
Clean up comments.

Who changed what in which revision?

UserRevisionLine numberNew contents of line
bw 0:bbf6cf0eab95 1 /*******************************************************************************
bw 0:bbf6cf0eab95 2 * Implements FIFO buffer for glitch-free audio playback.
bw 0:bbf6cf0eab95 3 * Bryan Wade
bw 0:bbf6cf0eab95 4 * 27 MAR 2014
bw 0:bbf6cf0eab95 5 ******************************************************************************/
bw 0:bbf6cf0eab95 6 #include "buffer.h"
bw 0:bbf6cf0eab95 7 #include "string.h"
bw 0:bbf6cf0eab95 8
bw 0:bbf6cf0eab95 9 struct buffer_t { // Implementation of opaque type.
bw 0:bbf6cf0eab95 10 int16_t *base;
bw 0:bbf6cf0eab95 11 int16_t *head;
bw 0:bbf6cf0eab95 12 int16_t *tail;
bw 0:bbf6cf0eab95 13 size_t len;
bw 0:bbf6cf0eab95 14 };
bw 0:bbf6cf0eab95 15
bw 0:bbf6cf0eab95 16 /*
bw 0:bbf6cf0eab95 17 * Create a buffer object given a ptr and size of available RAM.
bw 0:bbf6cf0eab95 18 * @return Ptr to the new buffer.
bw 0:bbf6cf0eab95 19 */
bw 0:bbf6cf0eab95 20 buffer_t *Buffer_Create(void *ram, size_t size)
bw 0:bbf6cf0eab95 21 {
bw 0:bbf6cf0eab95 22 buffer_t *buffer = (buffer_t *)malloc(sizeof(buffer_t));
bw 0:bbf6cf0eab95 23 if (buffer) {
bw 0:bbf6cf0eab95 24 buffer->base = (int16_t *)ram;
bw 0:bbf6cf0eab95 25 buffer->len = size / sizeof(int16_t);
bw 0:bbf6cf0eab95 26 memset(ram, 0, size);
bw 0:bbf6cf0eab95 27 buffer->head = buffer->tail = buffer->base;
bw 0:bbf6cf0eab95 28 }
bw 0:bbf6cf0eab95 29 return buffer;
bw 0:bbf6cf0eab95 30 }
bw 0:bbf6cf0eab95 31
bw 0:bbf6cf0eab95 32 /*
bw 0:bbf6cf0eab95 33 * Read a single sample from the buffer.
bw 0:bbf6cf0eab95 34 * @return True if successful (no underflow).
bw 0:bbf6cf0eab95 35 */
bw 0:bbf6cf0eab95 36 bool Buffer_Read(buffer_t *buffer, int16_t *pDataOut)
bw 0:bbf6cf0eab95 37 {
bw 0:bbf6cf0eab95 38 if (buffer->head == buffer->tail)
bw 0:bbf6cf0eab95 39 return false;
bw 0:bbf6cf0eab95 40
bw 0:bbf6cf0eab95 41 *pDataOut = *buffer->tail;
bw 0:bbf6cf0eab95 42
bw 0:bbf6cf0eab95 43 if (++buffer->tail >= buffer->base + buffer->len) {
bw 0:bbf6cf0eab95 44 buffer->tail = buffer->base;
bw 0:bbf6cf0eab95 45 }
bw 0:bbf6cf0eab95 46
bw 0:bbf6cf0eab95 47 return true;
bw 0:bbf6cf0eab95 48 }
bw 0:bbf6cf0eab95 49
bw 0:bbf6cf0eab95 50 /*
bw 0:bbf6cf0eab95 51 * Write a single sample to the buffer.
bw 0:bbf6cf0eab95 52 */
bw 0:bbf6cf0eab95 53 void Buffer_Write(buffer_t *buffer, int16_t dataIn)
bw 0:bbf6cf0eab95 54 {
bw 0:bbf6cf0eab95 55 if (Buffer_GetLevel(buffer) >= buffer->len - 1)
bw 0:bbf6cf0eab95 56 return;
bw 0:bbf6cf0eab95 57
bw 0:bbf6cf0eab95 58 *buffer->head = dataIn;
bw 0:bbf6cf0eab95 59
bw 0:bbf6cf0eab95 60 if (++buffer->head >= buffer->base + buffer->len)
bw 0:bbf6cf0eab95 61 buffer->head = buffer->base;
bw 0:bbf6cf0eab95 62 }
bw 0:bbf6cf0eab95 63
bw 0:bbf6cf0eab95 64 /*
bw 0:bbf6cf0eab95 65 * Write a block of data to the buffer.
bw 0:bbf6cf0eab95 66 */
bw 0:bbf6cf0eab95 67 void Buffer_WriteBlock(buffer_t *buffer, const int16_t *pDataIn, uint32_t length)
bw 0:bbf6cf0eab95 68 {
bw 0:bbf6cf0eab95 69 int i;
bw 0:bbf6cf0eab95 70 for (i = 0; i < length; i++) {
bw 0:bbf6cf0eab95 71 Buffer_Write(buffer, pDataIn[i]);
bw 0:bbf6cf0eab95 72 }
bw 0:bbf6cf0eab95 73 }
bw 0:bbf6cf0eab95 74
bw 0:bbf6cf0eab95 75 /*
bw 0:bbf6cf0eab95 76 * Get buffer level
bw 0:bbf6cf0eab95 77 */
bw 0:bbf6cf0eab95 78 int32_t Buffer_GetLevel(buffer_t *buffer)
bw 0:bbf6cf0eab95 79 {
bw 0:bbf6cf0eab95 80 __disable_irq(); /* Begin critical section */
bw 0:bbf6cf0eab95 81
bw 0:bbf6cf0eab95 82 int32_t level = (buffer->head >= buffer->tail) ?
bw 0:bbf6cf0eab95 83 buffer->head - buffer->tail :
bw 0:bbf6cf0eab95 84 buffer->len + buffer->head - buffer->tail;
bw 0:bbf6cf0eab95 85
bw 0:bbf6cf0eab95 86 __enable_irq(); /* End critical section */
bw 0:bbf6cf0eab95 87
bw 0:bbf6cf0eab95 88 return level;
bw 0:bbf6cf0eab95 89 }