Diff: main.cpp

Revision:

0:11b9454d32eb

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/main.cpp	Wed Dec 09 13:25:08 2020 +0000
@@ -0,0 +1,57 @@
+/* 
+
+2645_InterruptIn
+
+Sample code from ELEC2645 
+
+Demonstrates how to use InterruptIn to generate an event-triggered interrupt
+
+(c) Craig A. Evans, University of Leeds, Dec 2020
+
+*/ 
+
+#include "mbed.h"
+
+// Create objects for button A and LED1
+InterruptIn buttonA(p29);
+DigitalOut led(LED1);
+
+// flag - must be volatile as changes within ISR
+// g_ prefix makes it easier to distinguish it as global
+volatile int g_buttonA_flag = 0;
+
+// function prototypes
+void buttonA_isr();
+
+int main()
+{
+    // Button A has a pull-down resistor, so the pin will be at 0 V by default
+    // and rise to 3.3 V when pressed. We therefore need to look for a rising edge
+    // on the pin to fire the interrupt
+    buttonA.rise(&buttonA_isr);
+    // since Button A has an external pull-down, we should disable to internal pull-down
+    // resistor that is enabled by default using InterruptIn
+    buttonA.mode(PullNone);
+
+    while (1) {
+
+        // check if flag i.e. interrupt has occured
+        if (g_buttonA_flag) {
+            g_buttonA_flag = 0;  // if it has, clear the flag
+
+            // send message over serial port - can observe in CoolTerm etc.
+            printf("Execute task \n");
+            // DO TASK HERE
+        }
+
+        // put the MCU to sleep until an interrupt wakes it up
+        sleep();
+
+    }
+}
+
+// Button A event-triggered interrupt
+void buttonA_isr()
+{
+    g_buttonA_flag = 1;   // set flag in ISR
+}