Revision 111:ac492142f160, committed 2021-10-28

Comitter:

CSTritt

Date:

Thu Oct 28 02:28:59 2021 +0000

Parent:

110:e80444a6fe3a

Commit message:

First version. Demo of PWM setup and speaker operation.

Changed in this revision

--- a/main.cpp	Tue Oct 05 13:18:23 2021 +0000
+++ b/main.cpp	Thu Oct 28 02:28:59 2021 +0000
@@ -1,45 +1,32 @@
 /*
-    Project: 21_BC_Improved_v5 (Improved Binary Counter (while loop) Version)
+    Project: 21_Speaker_v5
     File: main.cpp
-    
-    Displays 8-bit binary count on bar graph display. This version uses a while 
-    loop which provides a much better starting point for an Up/Down counter.
-    
-    Error in pow function use corrected in v. 1.0.
-    
-    Note: I tried to use count for the loop counter but this resulted in an 
-    ambiguous name error.
-        
+
+    Use PWM to sound speaker audio alarm.
+
     Written by: Dr. C. S. Tritt
-    Created: 10/5/21 (v. 1.1)
+    Created: 10/27/21 (v. 1.0)
 */
 #include "mbed.h"
 
-DigitalIn uB(USER_BUTTON); // Button is active low (up = 1, down = 0).
-const int bits = 8; // Number of bits to use.
-const int c_max = pow(2, bits) - 1; // Maximum count. pow is type double.
-const int sleepTime = 100; // Sleep time in milliseconds.
-int myCount = 0; // Count to be displayed. Loop counter.
-BusOut barGraph(D2, D3, D4, D5, D6, D7, D8, D9);  // The display.
+DigitalIn uB(USER_BUTTON); // The user button input (normally high).
+PwmOut spkrOut(D12); // The speaker output.
 
-int main() {
-    // Test the wiring.
-    ThisThread::sleep_for(400); // For 0.4 seconds.
-    barGraph = 0b01010101;  // Odd bars on (binary).
-    ThisThread::sleep_for(400); // Test even bars for 0.4 seconds. 
-    barGraph = 0b10101010;  // Even bars on (binary).   
-    ThisThread::sleep_for(400); // Test even bars for 0.4 seconds.
-    barGraph = 0xFF;  // All bars on. Hex.
-    ThisThread::sleep_for(400); // For 0.4 seconds.  
-
-    barGraph = myCount; // Initialize the display to myCount.
-    // Enter main loop. 
+const int SLP_TIME = 100; // 0.1 s sample interval.
+// PWM period: 2500 uS = 2.5 mS --> 400 Hz.
+const int PWM_PRD = 2500; 
+const float DUTY_CYCLE = 0.5f; // Duty cycle as a fraction.
+int main(void)
+{
+    // Setup.
+    spkrOut.period_us(PWM_PRD);
+    // Enter main loop.
     while(true) {
-        while (myCount >= 0 && myCount <= c_max) {
-            barGraph = myCount; // Set display to myCount.
-            ThisThread::sleep_for(sleepTime);  // Display value for 0.1 seconds.
-            myCount++;
+        if (uB) {
+            spkrOut.write(0); // No sound.
+        } else {
+            spkrOut.write(DUTY_CYCLE); // Set duty cycle to sound speaker.            
         }
-        myCount = 0;
+        ThisThread::sleep_for(SLP_TIME);  // Display value for 0.1 seconds.            
     }
 }
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