Diff: main.cpp

Revision:

0:a9ab98434bf2

Child:

1:02d3732e1d76

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/main.cpp	Wed Dec 31 17:33:10 2014 +0000
@@ -0,0 +1,84 @@
+#include "mbed.h"
+
+PwmOut mypwm(PWM_OUT);          // This is the TX pulse pin
+AnalogIn adc1(PA_0);              // This is the ADC pin
+PwmOut buzzer(PC_9);             // This is the digital out pin connected to the buzzer
+InterruptIn event(PA_0);          // This sets a semaphore on rising front of pulse pin
+DigitalIn button(USER_BUTTON);
+Timeout timer;                  // This sets the net reading period
+
+float reading;                  // most current ADC capture value (0.0 to 1.0)
+bool sema, end_period;
+
+// system parameters
+float Gradient_Threshold = 0.05;    // audio threshold 
+int reading_period = 10000;         // in µsec
+int integration_ratio = 10;
+int pulse_period = 207;
+int pulse_width = 200;
+
+
+void read_one_pulse () {
+    sema = false;
+    while (!sema)
+        ;
+    reading += adc1.read();
+    }
+
+void trigger () {
+    sema = true;
+    }
+
+void TO() {
+   end_period = true;
+   }
+   
+int main() {
+ 
+
+float ref_reading;          // Reference reading of grounf signal
+int sample_count;
+int n, delta;
+
+  
+    mypwm.period_us(pulse_period);
+    mypwm.pulsewidth_us(0);
+    buzzer.period_ms(0);
+    buzzer.write(50);
+    event.rise(&trigger);
+    
+    while (button == 1)     //Wait to start session until button is pressed and released
+        ;
+    while (button == 0)
+        ;       
+    sample_count = 0;
+    while(1) {
+        end_period = false;
+        reading = 0;
+        timer.attach_us(&TO,reading_period);
+        mypwm.pulsewidth_us(pulse_width);       // Start TX pulses
+        for (n=0;n<integration_ratio;n++)
+            read_one_pulse();                   // Accumulate ADC captures into reading
+        mypwm.pulsewidth_us(0);                 // Stop TX pulses
+        reading /= integration_ratio;           // Average reading
+        if (sample_count == 0) {                // If first reading of session, save reading into ground reference signal level
+            ref_reading = reading;
+            sample_count++;
+            }
+        delta = reading - ref_reading;          // Delta is the gradient
+        if (abs(delta) > Gradient_Threshold )   // if hte graient is larger than a threshold, start buzzing
+            buzzer.period_ms(1);
+        else 
+            buzzer.period_ms(0);
+        if (delta != 0 && abs(delta) <= 0.01 )  // If delta is small enough but not nul, update the ref_reading with th ecurrent reading through a powerful low pass FIR filter.
+            ref_reading = (ref_reading*127 + reading ) / 128;
+        if (button == 0) {                      // pushing again on the button and relasing it stops the session
+            while (button == 0)
+                ;
+            return(0);
+            }
+        while (!end_period)             // Wait for end of reading period (i.e. 10msec)
+            ;
+      }
+}
+