Key detection and sinusoidal signal output developed by Arduino

Prepare the material ：

        Arduino Uno * 1

        Key *2

        resistance (860Ω)*2

        The steering gear *1

Circuit connection ：

        

        Be careful ： The button should be connected with pull-up resistance . Otherwise, the level will change randomly , Cause detection error .

Experimental code ：

        

double pi = 3.14159265354;
double t = 0.0;       // Company :s
double dt = 0.0;    // Company :s  

unsigned long nLastTime = 0;
int pulse = 0;
float w = 0.1;

int pwm_channel = 3;
int freq_channel = 7;
int begin_channel = 5;

int adn_pmax = 254;
int adn_pmin = 128;
int delta_adn_pwm = 0;
int adn_pmid = 0;
int pwm_out_min = 180;
int pwm_out_max = 206;
int pwm_out_mid = 193;

float cnt =  1.0;
float last_cnt;
int stage = 0;

void setup() {
  // put your setup code here, to run once:
  Serial.begin(115200);
  
  pinMode(pwm_channel,OUTPUT);
  pinMode(freq_channel,INPUT);
  pinMode(begin_channel,INPUT);

  nLastTime = micros();  
  
}

void loop() {
  // put your main code here, to run repeatedly:
  
  int freq_val  = digitalRead(freq_channel);
  int begin_val = digitalRead(begin_channel);

  if(stage == 0)
    if(freq_val == LOW){
      stage = 1;    
    }
  if(stage == 1)
    if(freq_val == HIGH){
      cnt++;
      stage = 0;
  }
 
  if(w<1){
    w = (cnt / 10);
  }
  else if( (w>=1) && (w<10) ){
     if(last_cnt != cnt){
        w = w + 1.0;
     }
  }
  else{
     if(last_cnt != cnt){
        w = w + 10.0;
     }
  } 
  
  last_cnt = cnt;
    
//  Serial.print(cnt); Serial.print('\t');
  double nNowTime = micros();     // Company : Microsecond 
  dt = (nNowTime - nLastTime)/1e6;
  t = t + dt + 6.6e-5;
  nLastTime = micros();     // Company : Microsecond 

  Serial.print(w); Serial.print('\t');
  if(begin_val == LOW){
    pulse = int(pwm_out_mid + 0.5*(pwm_out_max-pwm_out_min)*sin(2*pi*w*t));
    constrant();
  }
  else{
    pulse = pwm_out_mid;
  }
  
  analogWrite(pwm_channel,pulse);
  
  Serial.print(pulse); Serial.print('\t');

  Serial.print(dt); Serial.print('\t');

  Serial.println(t,6);
  
}

void constrant(void){
  if(pulse>=pwm_out_max)
    pulse = pwm_out_max;
  if(pulse<=pwm_out_min)
    pulse = pwm_out_min;
}

Key points of the experiment ：

        1. The key count is not only to determine whether to press , Also determine whether to lift , Otherwise, the counter will accumulate madly .

        2. Specific frequency sinusoidal signal output ,Ts stay Te after , The closer we get Te The better ,dt The smaller the error . Code in Figure dt The error of is .”Ts = micros()“  Record the timer value at the current time , Until the next cycle “Te = micro()” The execution time of all statements between is counted . So the error is two “dt = double((Te - Ts)/1e6);t = t + dt;” Statement execution time , add 6.6e-5 Just compensate for the error of these two sentences .

experimental result ：

        The output data is stored in matlab Draw it up . give the result as follows ：

 

          The picture above shows 1Hz Sinusoidal signal output of , It can be seen that the time difference between the two peaks is 1s about . The second peak is not sharp enough, which is caused by quantization error .