C. Lindsey Meadors
Simple mbed amplifier for quarter-inch audio input with volume, delay, and distortion control from smartphone app via bluetooth.
Revision 0:a487ac94eb85, committed 2017-05-02
- Comitter:
- lindseysix
- Date:
- Tue May 02 00:28:13 2017 +0000
- Commit message:
- Prototype amplifier with effects and smartphone control via bluetooth
Changed in this revision
--- /dev/null Thu Jan 01 00:00:00 1970 +0000
+++ b/main.cpp Tue May 02 00:28:13 2017 +0000
@@ -0,0 +1,104 @@
+//Library includes
+#include "mbed.h"
+#include "rtos.h"
+
+#define MAX_DELAY 10000 //Max size of delay effect sample buffer(too large can crash on compile from memory limit)
+
+//mbed pin declarations
+
+AnalogIn pot(p20);
+DigitalOut led(LED1);
+DigitalOut led2(LED2);
+AnalogIn input(p15);
+AnalogOut output(p18);
+Serial pc(USBTX, USBRX);
+Serial blue(p13,p14);
+
+//global variable declarations
+
+int inv_gain = 3; //scale factor for decreasing delay volume
+int delay = 0; //store value for delay from smartphone app
+float volume = .5; //store value for volume from smartphone app
+float distortion = 1.0; //store value for distortion from smartphone app
+unsigned short buffer[MAX_DELAY]; //declare array for storing samples for delay effect
+int scaleFactor = 30; //global to convert int values from smartphone app sliders
+
+/*******************************************************
+ Bluetooth thread for reading input from smartphone app
+********************************************************/
+void threadBluetooth(void const *args)
+{
+ while(1)
+ {
+ if(blue.readable()) //check if new value is available
+ {
+ int changeVal; //variable to hold value from smartphone app
+ changeVal = blue.getc(); //get new value from app via bluetooth
+
+ if(changeVal <= scaleFactor) //check if new value falls in volume slider range
+ {
+ //convert volume to float value in range [0.0-1.0]
+ volume = (float)changeVal/((float)scaleFactor+3);
+ }
+ else if(changeVal <= scaleFactor*2) //check if value is in delay range
+ {
+ //convert delay to float in range (0.0 - 1.0]
+ delay = ((float)changeVal-((float)scaleFactor+1))/((float)scaleFactor)*MAX_DELAY;
+
+ if(changeVal == 31) //if new value is bottom of delay slider
+ {
+ delay = 0; //set delay to zero (disable effect)
+ }
+ }
+ else if(changeVal <= scaleFactor*3) //check if value is in distortion range
+ {
+ //convert distortion to float in range (3.0 - 4.0)
+ distortion = 3.0 + ((float)changeVal-(2*(float)scaleFactor+1))/((float)scaleFactor);
+
+ if(changeVal == 61) //if new value is bottom of distortion slider
+ {
+ distortion = 1; //set distortion to one (disable effect)
+ }
+ }
+ }
+ Thread::wait(100);
+} //end bluetooth thread
+
+/*****
+ Main
+*****/
+
+int main(void)
+{
+ Thread threadBlue(threadBluetooth); //startup Bluetooth thread for smartphone app
+ int oldDelay; //global for delay comparison
+
+ while(1)
+ {
+ int i; //for loop count variable
+
+ if(delay > 0) //check if delay effect is on
+ {
+ if(delay != oldDelay) //if delay value has changed re-buffer
+ {
+ for (i = 0; i < delay; i++) //buffer loop
+ {
+ buffer[i] += input.read_u16();
+ oldDelay = delay;
+ }
+ }
+ while(delay > 0) //while delay is on
+ {
+ buffer[i] = buffer[i]/inv_gain + input.read_u16(); //scale buffer value and add to input
+ output.write_u16(distortion * volume * buffer[i]); //write to output
+ i = (i+1) % delay; //traverse buffer array(use delay number of values)
+ }
+ }
+ else
+ {
+ //with no delay write input value scaled by volume and distortion
+ output.write_u16(distortion * volume * input.read_u16());
+ wait_us(23); //wait time based on sample rate
+ }
+ }
+} //end main
\ No newline at end of file
--- /dev/null Thu Jan 01 00:00:00 1970 +0000 +++ b/mbed-rtos.lib Tue May 02 00:28:13 2017 +0000 @@ -0,0 +1,1 @@ +https://mbed.org/users/mbed_official/code/mbed-rtos/#58563e6cba1e
--- /dev/null Thu Jan 01 00:00:00 1970 +0000 +++ b/mbed.bld Tue May 02 00:28:13 2017 +0000 @@ -0,0 +1,1 @@ +https://mbed.org/users/mbed_official/code/mbed/builds/794e51388b66 \ No newline at end of file