HM Yoong
This example illustrates the use of simple stage machine to handle event within mbed. When any of the 3 push button is pressed, the stage (number) will be shown via the on-board LEDs. {{/media/uploads/yoonghm/state_machine_example.jpg}}
Diff: main.cpp
- Revision:
- 0:8e509fb9a48c
- Child:
- 1:8cfb6bfdb4e0
--- /dev/null Thu Jan 01 00:00:00 1970 +0000
+++ b/main.cpp Wed Dec 07 10:10:02 2011 +0000
@@ -0,0 +1,98 @@
+#include "mbed.h"
+
+/* Various states */
+typedef enum tState
+{
+ STATE_A,
+ STATE_B,
+ STATE_C
+} tState;
+
+/* Variables */
+tState state; /* Current state */
+char trigger; /* Bit set to indicate which button triggers */
+
+InterruptIn button1(p5); /* interrupt for button 1 at pin 5 */
+InterruptIn button2(p6); /* interrupt for button 1 at pin 6 */
+InterruptIn button3(p7); /* interrupt for button 1 at pin 7 */
+BusOut task(LED1, LED2, LED3, LED4);
+
+/* Interrupt handlers when buttons is pressed */
+void int_button1() {trigger |= 0x01;}
+void int_button2() {trigger |= 0x02;}
+void int_button3() {trigger |= 0x04;}
+
+/* task to be executed during each state transition */
+void do_task(int n) {task = n; wait(2.0); task = 0;}
+
+void sleep(void) {__WFI();} /* Power-saving sleeping mode */
+
+
+int main()
+{
+ /* Enable pull-down resistor for each button */
+ button1.mode(PullDown);
+ button2.mode(PullDown);
+ button3.mode(PullDown);
+
+ /* Assign ISR to each button */
+ button1.rise(&int_button1);
+ button2.rise(&int_button2);
+ button3.rise(&int_button3);
+
+ /* initial the state machine */
+ state = STATE_A;
+
+ while(1)
+ {
+ /* While I am not triggered, sleep */
+ while (!trigger)
+ sleep();
+
+ /* I am awake now. Check which button has triggered*/
+ switch (state)
+ {
+ //////////////////////////////////////////////////////////////////
+ case STATE_A: ///////////////////////////////////////////////////
+ //////////////////////////////////////////////////////////////////
+ if (trigger & 0x01) /* Button 1 down */
+ {
+ do_task(1);
+ state = STATE_B; /* Transit to STATE_B */
+ }
+ trigger = 0; /* Ignore other triggers in this state */
+ break;
+
+ //////////////////////////////////////////////////////////////////
+ case STATE_B: ///////////////////////////////////////////////////
+ //////////////////////////////////////////////////////////////////
+ if (trigger & 0x01) /* Button 1 down */
+ {
+ do_task(2);
+ state = STATE_A;
+ }
+ if (trigger & 0x02) /* Button 2 down */
+ {
+ do_task(3);
+ /* Remain in the same state */
+ }
+ if (trigger & 0x04) /* Button 3 down */
+ {
+ do_task(4);
+ state = STATE_C;
+ }
+ trigger = 0; /* Ignore other triggers in this state */
+ break;
+
+ //////////////////////////////////////////////////////////////////
+ case STATE_C: ///////////////////////////////////////////////////
+ //////////////////////////////////////////////////////////////////
+ if (trigger & 0x04) /* Button 3 down */
+ {
+ do_task(5);
+ state = STATE_A;
+ }
+ break;
+ } /* while (!trigger) */
+ } /* while (1) */
+}