Wave Player Using DMA

Page last updated 07 Nov 2016, by Nathan Somavarapu. 0 replies

Introduction

This project uses a common Wave Player library and a micro SD card library to play a song that is located on a micro SD Card. Instead of just reading the file byte by byte this library includes an improvement by using the MODDMA library to transfer an entire buffer from the micro SD card to the DAC.

Wiring Information

Micro SD Card Module

micro SDCard module pinMBed pin
CS8
DI5
VCCVOUT
SCK7
GNDGND
DO6
CDany Digital Out pin (10 was used)

Class D high-efficiency audio amp

This module is optional instead of using this amp the speaker can be used with a simple transistor as shown in:

https://developer.mbed.org/media/uploads/4180_1/x_scaled_speakerdriverschem.png.pagespeed.ic.ZyP3lIY8da.png.

The amp that was used was the TI TPA2005D1 class D audio amp chip (250Khz PWM) sold by Sparkfun: TI TPA2005D1.

AMP pinsMBed pin
PWR -GND
IN -GND
PWR +VOUT(3.3V or 5V)
IN +p26
PWR +VOUT(3.3V or 5V)
SAny Digital Out(optional)
AMP pinsSpeaker Pins
OUT ++
OUT --

Code

Below is the code for the Wave Player example. You can see that it is the same as before all of the DMA code has been included in the background in the play method. Below is the link to the library with play method using DMA

#include "mbed.h"
#include "SDFileSystem.h"
#include "wave_player.h"


SDFileSystem sd(p5, p6, p7, p8, "sd"); //SD card

AnalogOut DACout(p18);

wave_player waver(&DACout);

int main()
{
    FILE *wave_file;
    printf("\n\n\nHello, wave world!\n");
    wave_file=fopen("/sd/sample.wav","r");
    waver.play(wave_file);
    fclose(wave_file);
}

Import programwave_player_DMA_mbed

Wave Player with DMA

Last commit 16 Mar 2016 by Nathan Somavarapu

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