Diff: main.cpp

Revision:

0:a8167a8804f5

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/main.cpp	Thu Jan 07 14:03:12 2016 +0000
@@ -0,0 +1,36 @@
+/** 08_button_debouncer
+ *
+ * Switches a LED on/off by pushbutton.
+ * The state of the button is sampled by a Ticker timer
+ * in each 20 ms and thus the button is debounced.
+ * This program can be regarded as an improved version
+ * of 07_button_interrupt program.
+ *
+ * Hardware requirements:
+ *  - FRDM-KL25Z board
+ *  - Pusbutton (tied between D3 and GND)
+ */
+
+#include "mbed.h"
+
+DigitalIn button(D3,PullUp);            // Pusbutton input
+DigitalOut led(LED_BLUE);               // LED output (the blue LED)
+Ticker sampler;                         // Ticker for button state sampling
+volatile uint8_t button_state = 1;      // Initially released
+
+void button_check()
+{
+    button_state = (button_state<<1) | (button & 1); // shift in button state
+    if((button_state & 3)==2) {         // Check for H -> L transition
+        led = !led;                     // Switch LED state
+    }
+}
+
+int main()
+{
+    led = 1;                            // LED off
+    sampler.attach(&button_check,0.02); // sample button state in each 20 ms
+    while (true) {
+        wait(1);                        // do nothing
+    }
+}
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