refactor(Debounce, Error handling):

Modified:
- Debounce Algorithm
- Result Printings
- Formatting

lab_3/lab_3.c

@@ -1,17 +1,31 @@
 /**
  * Lab 3
- * To develop a simple stopwatch that measures time intervals between
- * button presses.
  *
- * On pressing the START pseudo-button (GP15),
- * the stopwatch will begin,
- * and the elapsed time will be displayed every second on
- * the Serial Monitor (or equivalent).
+ * This is my solution to the lab 3 assignment.
+ * There are multiple structs and enums defined in this file.
  *
- * Releasing the START pseudo-button will stop the timer and
- * reset the elapsed time to zero.
+ * time_struct is used to store the start time and current time for
+ * time calculations.
  *
- * The START pseudo-button must incorporate a debouncing algorithm.
+ * btn_status struct is used to keep track of the number of times the
+ * button is pressed and released. This is used to implement a debounce
+ * algorithm.
+ *
+ * btn_state enum is used to return the states of the button, used to check
+ * for errors and to return the state of the button.
+ *
+ * This firmware will use GPIO 15 as a pseudo-button (pull-up) and
+ * will start a timer on button press (falling edge) and stop the timer
+ * on button release (rising edge).
+ *
+ * The Timer will print the elapsed time every second as required by the
+ * lab specification.
+ *
+ * The DEBOUNCE_US macro is used to set the debounce delay to 20ms, the value
+ * can be refined to get more accurate results.
+ *
+ * This is made more complex with the use of interrupts, timers and a debounce
+ * algorithm.
  *
  */
 
@@ -21,21 +35,26 @@
 
 #define PSEUDO_BTN  15          // GPIO 15 is the pseudo-button
 #define TIMER_US    1000000     // 1-second delay for repeating timer
-#define DEBOUNCE_US 100         // 100us debounce time
+#define DEBOUNCE_US 20000       // 20ms debounce delay
 
 struct repeating_timer timer;   // Repeating timer
-u_int64_t time = 0;             // Elapsed time
 
-typedef enum btn_state {        // Button state
-    PRESSED = 0,
-    RELEASED = 1
-} btn_state_t;
+struct time_struct {            // Time struct (Used for time calculations)
+    uint64_t start_time;
+    uint64_t current_time;
+} time_struct = {0, 0};
 
-struct btn_status {             // Button status
+struct btn_status {             // Button status (Used to implement debounce)
     uint btn_pressed;
     uint btn_released;
 } btn_status = {0, 0};
 
+typedef enum btn_state {        // Button state (Used as return value)
+    ERROR = -1,
+    PRESSED = 0,
+    RELEASED = 1
+} btn_state_t;
+
 /**
  * Callback function for repeating timer
  * This function will print the elapsed time every second as required by the
@@ -44,9 +63,14 @@ struct btn_status {             // Button status
  * @return     True to keep the timer running, false to stop it
  */
 bool elapsed_time_callback (struct repeating_timer *t) {
-    time++;
-    // Print elapsed time every second
-    printf("Elapsed Time: %llus\n", time);
+    time_struct.start_time = (time_struct.start_time == 0) ?
+                             time_us_64() : time_struct.start_time;
+
+    time_struct.current_time = time_us_64();
+
+    printf("%llus\n",
+           (time_struct.current_time - time_struct.start_time) / 1000000);
+
     return true;
 }
 
@@ -57,7 +81,13 @@ bool elapsed_time_callback (struct repeating_timer *t) {
  * @return The state of the pseudo-button
  */
 btn_state_t get_btn_state () {
+    if (btn_status.btn_pressed != 0 || btn_status.btn_released != 0)
+    {
+        return ERROR;
+    }
+
     u_int64_t start_time = time_us_64();
+
     while (time_us_64() - start_time < DEBOUNCE_US)
     {
         if (gpio_get(PSEUDO_BTN))
@@ -71,7 +101,7 @@ btn_state_t get_btn_state () {
     }
 
     btn_state_t state = (btn_status.btn_pressed > btn_status.btn_released) ?
-                           PRESSED : RELEASED;
+                        PRESSED : RELEASED;
 
     // Reset btn_status
     btn_status = (struct btn_status) {0, 0};
@@ -89,11 +119,15 @@ btn_state_t get_btn_state () {
 void gpio_callback (uint gpio, uint32_t events) {
     btn_state_t btn_state = get_btn_state();
 
+    if (btn_state == ERROR)
+    {
+        printf("Error: Button is bouncing\n");
+        return;
+    }
+
     if (events == GPIO_IRQ_EDGE_FALL && btn_state == PRESSED)
     {
-        printf("\n====================================\n");
         printf("Timer Started\n");
-        printf("====================================\n");
 
         add_repeating_timer_us(
                 TIMER_US,
@@ -101,31 +135,29 @@ void gpio_callback (uint gpio, uint32_t events) {
                 NULL,
                 &timer
         );
-
     }
 
     if (events == GPIO_IRQ_EDGE_RISE && btn_state == RELEASED)
     {
-        cancel_repeating_timer(&timer);
-
-        // Print elapsed time and reset
-        printf("\n====================================\n");
-        printf("Timer Stopped\n");
-        printf("====================================\n");
-        printf("Final Elapsed Time: %llus\n", time);
-        printf("====================================\n");
-
-        time = 0;
+        if (cancel_repeating_timer(&timer))
+        {
+            printf("Timer Stopped\n");
+            printf("Final Elapsed Time: %llus\n",
+                   (time_struct.current_time - time_struct.start_time) /
+                   1000000);
+        }
 
+        time_struct = (struct time_struct) {0, 0};
     }
 }
 
 /**
  * Initialize the pseudo-button (pull-up)
- * The pseudo-button is connected to GPIO 15 and is configured as
- * an input with a pull-up resistor.
- * The interrupt is configured to trigger on both rising and
- * falling edges.
+ * The pseudo-button is connected to GPIO 15 and
+ * is configured as an input with a pull-up resistor.
+ *
+ * The interrupt is configured to trigger on both
+ * rising and falling edges.
  */
 static void btn_init () {
     gpio_init(PSEUDO_BTN);