Diff: main.cpp

Revision:

0:b3c72630f04c

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/main.cpp	Fri Feb 07 20:18:51 2020 +0000
@@ -0,0 +1,81 @@
+/*
+Exercise : Create a PWM signal which we can see on an
+oscilloscope. The following code will generate a 100 Hz
+pulse with 50% duty cycle
+*/
+
+
+#include "mbed.h"
+PwmOut PWM1(p21);
+int main()
+{
+    PWM1.period(0.010); // set PWM period to 10 ms
+    PWM1=0.5; // set duty cycle to 50%
+}
+
+/*
+Exercise : This example code uses a pulse width
+modulation signal to increase and decrease
+the brightness of the onboard LED
+The program requires the use of a host terminal
+application to communicate the
+brightness value to the mbed, in this example by
+using the ‘u’ and ‘d’ keys
+*/
+
+
+
+// host terminal LED dimmer control
+#include "mbed.h"
+Serial pc(USBTX, USBRX); // tx, rx
+PwmOut led(LED1);
+float brightness=0.0;
+int main()
+{
+    pc.printf(“Control of LED dimmer by host terminal\n\r");
+              pc.printf("Press 'u‘ = brighter, 'd‘ = dimmer\n\r");
+    while(1) {
+    char c = pc.getc();
+        wait(0.001);
+        if((c == 'u') && (brightness < 0.1)) {
+            brightness += 0.001;
+            led = brightness;
+        }
+        if((c == 'd') && (brightness > 0.0)) {
+            brightness -= 0.001;
+            led = brightness;
+        }
+        pc.printf("%c %1.3f \n \r",c,brightness);
+    }
+}
+
+/*
+
+Exercise 7: We are going to use the PWM to play the start of an
+old English folk tune ‘Oranges and Lemons’. If you’re a reader of
+music you will recognise this in the Figure below
+• You just need to know that any note which is a minim lasts twice
+as long as a crotchet, which in turn lasts twice as long as a quaver 
+
+The following program implements the ‘Oranges and Lemons‘ musical
+output
+*/
+
+// Oranges and Lemons program
+#include "mbed.h"
+PwmOut buzzer(p21);
+float frequency[]= {659,554,659,554,550,494,554,587,494,659,554,440};
+//frequency array
+float beat[]= {1,1,1,1,1,0.5,0.5,1,1,1,1,2};
+//beat array
+int main()
+{
+    while (1) {
+        for (int i=0; i<=11; i++) {
+            buzzer.period(1/(frequency[i])); // set PWM period
+            buzzer=0.5; // set duty cycle
+            wait(0.5*beat[i]); // hold for beat period
+        }
+    }
+}
+