feature(Lab 3):

Lab 3 done:
- Start and stop time
- stopwatch component done

Missing:
- Debounce button on START

lab_3/CMakeLists.txt

@@ -0,0 +1,51 @@
+# Generated Cmake Pico project file
+
+cmake_minimum_required(VERSION 3.13)
+
+set(CMAKE_C_STANDARD 11)
+set(CMAKE_CXX_STANDARD 17)
+
+# Initialise pico_sdk from installed location
+# (note this can come from environment, CMake cache etc)
+set(PICO_SDK_PATH "/home/junwei/Documents/pico/pico-sdk")
+
+set(PICO_BOARD pico_w CACHE STRING "Board type")
+
+# Pull in Raspberry Pi Pico SDK (must be before project)
+include(pico_sdk_import.cmake)
+
+if (PICO_SDK_VERSION_STRING VERSION_LESS "1.4.0")
+  message(FATAL_ERROR "Raspberry Pi Pico SDK version 1.4.0 (or later) required. Your version is ${PICO_SDK_VERSION_STRING}")
+endif()
+
+project(lab_3 C CXX ASM)
+
+# Initialise the Raspberry Pi Pico SDK
+pico_sdk_init()
+
+# Add executable. Default name is the project name, version 0.1
+
+add_executable(lab_3 lab_3.c )
+
+pico_set_program_name(lab_3 "lab_3")
+pico_set_program_version(lab_3 "0.1")
+
+pico_enable_stdio_uart(lab_3 1)
+pico_enable_stdio_usb(lab_3 1)
+
+# Add the standard library to the build
+target_link_libraries(lab_3
+        pico_stdlib)
+
+# Add the standard include files to the build
+target_include_directories(lab_3 PRIVATE
+  ${CMAKE_CURRENT_LIST_DIR}
+  ${CMAKE_CURRENT_LIST_DIR}/.. # for our common lwipopts or any other standard includes, if required
+)
+
+# Add any user requested libraries
+target_link_libraries(lab_3 
+        )
+
+pico_add_extra_outputs(lab_3)
+

lab_3/lab_3.c

@@ -0,0 +1,86 @@
+/**
+ * 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).
+ *
+ * Releasing the START pseudo-button will stop the timer and
+ * reset the elapsed time to zero.
+ *
+ * The START pseudo-button must incorporate a debouncing algorithm.
+ *
+ */
+
+#include <stdio.h>
+#include "pico/stdlib.h"
+#include "hardware/gpio.h"
+
+#define PSEUDO_BTN 15
+#define DELAY_US 1000000
+
+unsigned long long time = 0;
+struct repeating_timer timer;
+
+bool repeating_timer_callback(struct repeating_timer *t) {
+    // Print elapsed time every second
+    printf("Elapsed Time: %llus\n",
+           (time_us_64() - time) / 1000000);
+    return true;
+}
+
+
+void gpio_callback(uint gpio, uint32_t events) {
+    // Start timer on button press
+    if (gpio == PSEUDO_BTN && events == GPIO_IRQ_EDGE_FALL)
+    {
+        time = time_us_64();
+        printf("Timer Started at %llu\n", time);
+
+        add_repeating_timer_us(
+                DELAY_US,
+                repeating_timer_callback,
+                NULL,
+                &timer
+                );
+    }
+    // Stop timer on button release
+    else if (gpio == PSEUDO_BTN && events == GPIO_IRQ_EDGE_RISE)
+    {
+        printf("Timer Stopped at %llu\n", time_us_64());
+        cancel_repeating_timer(&timer);
+
+        // Print elapsed time and reset
+        printf("Final Elapsed Time: %llus\n",
+               (time_us_64() - time) / 1000000);
+
+        time = 0;
+    }
+}
+
+static void btn_init()
+{
+    gpio_init(PSEUDO_BTN);
+    gpio_set_dir(PSEUDO_BTN, GPIO_IN);
+    gpio_set_pulls(PSEUDO_BTN, true, false);
+
+    gpio_set_irq_enabled_with_callback(
+            PSEUDO_BTN,
+            GPIO_IRQ_EDGE_RISE | GPIO_IRQ_EDGE_FALL,
+            true,
+            &gpio_callback
+    );
+}
+
+int main()
+{
+    stdio_init_all();
+    btn_init();
+
+    while (true) {
+        tight_loop_contents();
+    }
+
+}