Generate Audio Tones

Firmware
7

@peekay123 and @satishgn your two pieces of code virtually do the whole job for me. Thank you very much indeed.
Thanks too to @bko and @bdub for pointing me in the right direction.
If the code is doing what I think it is, Iā€™m sampling the ADC at 8kHz and using the measured ADC value to PWM an LED at 40kHz in 100 steps. Now I just need to put in the digital delay line and the LMS algorithm. :sunny: :smile:

   
//antinoise.cpp
//0.001 - read ADC write to LED ....   OK
//0.002 - change frequency of PWM from 500Hz to 40kHz.... OK
//0.003 - blink LED on an interrupt ...OK
//0.004 - getADCvalue on interrupt ... OK
//0.005 - speed up interrupt to 8kHz...      OK

#include "application.h"
#include "SparkIntervalTimer.h"
int LED = D0;
int ADC = A0;
volatile int value;
IntervalTimer myTimer;

// Pre-define ISR callback function
void getADCvalue(void);

void setup(){
    // set up the timer that will obtain ADC values every 125 uSec (thanks peekay123)
    myTimer.begin(getADCvalue, 125, uSec, TIMER3); //v003 v004
    
    //set up the Spark PWM on pin D0 to operate at 40kHz (thanks satishgn)
    pinMode(LED, OUTPUT);
    analogWrite(LED,0);
    //Set the Prescaler value
    TIM4->PSC = 18; // 72M / 18 = 4M counts per sec, 4M / 100 = 40k values per sec
    //Load prescaler immediately
    TIM4->EGR = 1;
    //Set the Autoreload Register value
    TIM4->ARR = 100;
    //Set the Capture Compare2 Register value
    TIM4->CCR2 = 50;//CCR2 is for Channel 2 = D0
    
}

// Callback for Timer
void getADCvalue(void){
    value = analogRead(ADC);
    /////////////////////////////////
    //TODO - put LMS algorithm here!!
    /////////////////////////////////
    TIM4->CCR2 = value/41;//CCR2 is for Channel 2
}
void loop(){
    //value = analogRead(ADC);
    //analogWrite(LED,value/16); //v001
    //TIM4->CCR2 = value/41;//CCR2 is for Channel 2 //(4096 / 100 = 41 ish) v002
    //delay(10);
}```
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