C. Lindsey Meadors / Mbed 2 deprecated Bluetooth_Amplifier_with_Effects

Simple mbed amplifier for quarter-inch audio input with volume, delay, and distortion control from smartphone app via bluetooth.

Dependencies:   mbed-rtos mbed

main.cpp@0:a487ac94eb85, 2017-05-02 (annotated)

Committer:
lindseysix
Date:
Tue May 02 00:28:13 2017 +0000
Revision:
0:a487ac94eb85
Prototype amplifier with effects and smartphone control via bluetooth

Who changed what in which revision?

UserRevisionLine numberNew contents of line
lindseysix 0:a487ac94eb85 1 //Library includes
lindseysix 0:a487ac94eb85 2 #include "mbed.h"
lindseysix 0:a487ac94eb85 3 #include "rtos.h"
lindseysix 0:a487ac94eb85 4
lindseysix 0:a487ac94eb85 5 #define MAX_DELAY 10000 //Max size of delay effect sample buffer(too large can crash on compile from memory limit)
lindseysix 0:a487ac94eb85 6
lindseysix 0:a487ac94eb85 7 //mbed pin declarations
lindseysix 0:a487ac94eb85 8
lindseysix 0:a487ac94eb85 9 AnalogIn pot(p20);
lindseysix 0:a487ac94eb85 10 DigitalOut led(LED1);
lindseysix 0:a487ac94eb85 11 DigitalOut led2(LED2);
lindseysix 0:a487ac94eb85 12 AnalogIn input(p15);
lindseysix 0:a487ac94eb85 13 AnalogOut output(p18);
lindseysix 0:a487ac94eb85 14 Serial pc(USBTX, USBRX);
lindseysix 0:a487ac94eb85 15 Serial blue(p13,p14);
lindseysix 0:a487ac94eb85 16
lindseysix 0:a487ac94eb85 17 //global variable declarations
lindseysix 0:a487ac94eb85 18
lindseysix 0:a487ac94eb85 19 int inv_gain = 3; //scale factor for decreasing delay volume
lindseysix 0:a487ac94eb85 20 int delay = 0; //store value for delay from smartphone app
lindseysix 0:a487ac94eb85 21 float volume = .5; //store value for volume from smartphone app
lindseysix 0:a487ac94eb85 22 float distortion = 1.0; //store value for distortion from smartphone app
lindseysix 0:a487ac94eb85 23 unsigned short buffer[MAX_DELAY]; //declare array for storing samples for delay effect
lindseysix 0:a487ac94eb85 24 int scaleFactor = 30; //global to convert int values from smartphone app sliders
lindseysix 0:a487ac94eb85 25
lindseysix 0:a487ac94eb85 26 /*******************************************************
lindseysix 0:a487ac94eb85 27 Bluetooth thread for reading input from smartphone app
lindseysix 0:a487ac94eb85 28 ********************************************************/
lindseysix 0:a487ac94eb85 29 void threadBluetooth(void const *args)
lindseysix 0:a487ac94eb85 30 {
lindseysix 0:a487ac94eb85 31 while(1)
lindseysix 0:a487ac94eb85 32 {
lindseysix 0:a487ac94eb85 33 if(blue.readable()) //check if new value is available
lindseysix 0:a487ac94eb85 34 {
lindseysix 0:a487ac94eb85 35 int changeVal; //variable to hold value from smartphone app
lindseysix 0:a487ac94eb85 36 changeVal = blue.getc(); //get new value from app via bluetooth
lindseysix 0:a487ac94eb85 37
lindseysix 0:a487ac94eb85 38 if(changeVal <= scaleFactor) //check if new value falls in volume slider range
lindseysix 0:a487ac94eb85 39 {
lindseysix 0:a487ac94eb85 40 //convert volume to float value in range [0.0-1.0]
lindseysix 0:a487ac94eb85 41 volume = (float)changeVal/((float)scaleFactor+3);
lindseysix 0:a487ac94eb85 42 }
lindseysix 0:a487ac94eb85 43 else if(changeVal <= scaleFactor*2) //check if value is in delay range
lindseysix 0:a487ac94eb85 44 {
lindseysix 0:a487ac94eb85 45 //convert delay to float in range (0.0 - 1.0]
lindseysix 0:a487ac94eb85 46 delay = ((float)changeVal-((float)scaleFactor+1))/((float)scaleFactor)*MAX_DELAY;
lindseysix 0:a487ac94eb85 47
lindseysix 0:a487ac94eb85 48 if(changeVal == 31) //if new value is bottom of delay slider
lindseysix 0:a487ac94eb85 49 {
lindseysix 0:a487ac94eb85 50 delay = 0; //set delay to zero (disable effect)
lindseysix 0:a487ac94eb85 51 }
lindseysix 0:a487ac94eb85 52 }
lindseysix 0:a487ac94eb85 53 else if(changeVal <= scaleFactor*3) //check if value is in distortion range
lindseysix 0:a487ac94eb85 54 {
lindseysix 0:a487ac94eb85 55 //convert distortion to float in range (3.0 - 4.0)
lindseysix 0:a487ac94eb85 56 distortion = 3.0 + ((float)changeVal-(2*(float)scaleFactor+1))/((float)scaleFactor);
lindseysix 0:a487ac94eb85 57
lindseysix 0:a487ac94eb85 58 if(changeVal == 61) //if new value is bottom of distortion slider
lindseysix 0:a487ac94eb85 59 {
lindseysix 0:a487ac94eb85 60 distortion = 1; //set distortion to one (disable effect)
lindseysix 0:a487ac94eb85 61 }
lindseysix 0:a487ac94eb85 62 }
lindseysix 0:a487ac94eb85 63 }
lindseysix 0:a487ac94eb85 64 Thread::wait(100);
lindseysix 0:a487ac94eb85 65 } //end bluetooth thread
lindseysix 0:a487ac94eb85 66
lindseysix 0:a487ac94eb85 67 /*****
lindseysix 0:a487ac94eb85 68 Main
lindseysix 0:a487ac94eb85 69 *****/
lindseysix 0:a487ac94eb85 70
lindseysix 0:a487ac94eb85 71 int main(void)
lindseysix 0:a487ac94eb85 72 {
lindseysix 0:a487ac94eb85 73 Thread threadBlue(threadBluetooth); //startup Bluetooth thread for smartphone app
lindseysix 0:a487ac94eb85 74 int oldDelay; //global for delay comparison
lindseysix 0:a487ac94eb85 75
lindseysix 0:a487ac94eb85 76 while(1)
lindseysix 0:a487ac94eb85 77 {
lindseysix 0:a487ac94eb85 78 int i; //for loop count variable
lindseysix 0:a487ac94eb85 79
lindseysix 0:a487ac94eb85 80 if(delay > 0) //check if delay effect is on
lindseysix 0:a487ac94eb85 81 {
lindseysix 0:a487ac94eb85 82 if(delay != oldDelay) //if delay value has changed re-buffer
lindseysix 0:a487ac94eb85 83 {
lindseysix 0:a487ac94eb85 84 for (i = 0; i < delay; i++) //buffer loop
lindseysix 0:a487ac94eb85 85 {
lindseysix 0:a487ac94eb85 86 buffer[i] += input.read_u16();
lindseysix 0:a487ac94eb85 87 oldDelay = delay;
lindseysix 0:a487ac94eb85 88 }
lindseysix 0:a487ac94eb85 89 }
lindseysix 0:a487ac94eb85 90 while(delay > 0) //while delay is on
lindseysix 0:a487ac94eb85 91 {
lindseysix 0:a487ac94eb85 92 buffer[i] = buffer[i]/inv_gain + input.read_u16(); //scale buffer value and add to input
lindseysix 0:a487ac94eb85 93 output.write_u16(distortion * volume * buffer[i]); //write to output
lindseysix 0:a487ac94eb85 94 i = (i+1) % delay; //traverse buffer array(use delay number of values)
lindseysix 0:a487ac94eb85 95 }
lindseysix 0:a487ac94eb85 96 }
lindseysix 0:a487ac94eb85 97 else
lindseysix 0:a487ac94eb85 98 {
lindseysix 0:a487ac94eb85 99 //with no delay write input value scaled by volume and distortion
lindseysix 0:a487ac94eb85 100 output.write_u16(distortion * volume * input.read_u16());
lindseysix 0:a487ac94eb85 101 wait_us(23); //wait time based on sample rate
lindseysix 0:a487ac94eb85 102 }
lindseysix 0:a487ac94eb85 103 }
lindseysix 0:a487ac94eb85 104 } //end main