Updated (Testing Kalman Filter)

frtos/ultrasonic_sensor/ultrasonic_sensor.c

@@ -6,7 +6,10 @@
 #define TRIG_PIN 0
 #define ECHO_PIN 1
 
-void init_ultrasonic(void)
+int16_t counter = 0;
+
+void
+init_ultrasonic(void)
 {
     // Set up the echo pin
     gpio_init(ECHO_PIN);
@@ -17,11 +20,34 @@ void init_ultrasonic(void)
     gpio_set_dir(TRIG_PIN, GPIO_OUT);
 }
 
-void distance_task(__unused void *params)
+float
+KalmanFilter(float U)
+{
+    static float R = 10;    // noise convariance can be 10, higher better smooth
+    static float H = 1;     // Measurement Map scalar
+    static float Q = 10;    // initial estimated convariance
+    static float P = 0;     // initial error covariance
+    static float U_hat = 0; // initial estimated state
+    static float K     = 0; // initial Kalman gain
+
+    // Predict
+    //
+    K     = P * H / (H * P * H + R);     // Update Kalman gain
+    U_hat = U_hat + K * (U - H * U_hat); // Update estimated state
+
+    // Update error covariance
+    //
+    P = (1 - K * H) * P + Q;
+
+    return U_hat;
+}
+
+void
+distance_task(__unused void *params)
 {
     while (true)
     {
-        vTaskDelay(500);
+        vTaskDelay(1000);
 
         // Trigger the ultrasonic sensor
         gpio_put(TRIG_PIN, 1);
@@ -42,7 +68,9 @@ void distance_task(__unused void *params)
         uint32_t pulse_duration = end_time - start_time;
         float distance = pulse_duration * 0.017; // Speed of sound at ~343 m/s
 
-        printf("Distance: %.2f cm\n", distance);
+        // printf("Distance: %.2f cm\n", distance);
+        // printf("Kalman Filtered Distance: %.2f cm\n", KalmanFilter(distance));
+        printf("%d,%.2f,%.2f\n", counter++, distance, KalmanFilter(distance));
 
         // If gonna bang wall
         //
@@ -55,21 +83,28 @@ void distance_task(__unused void *params)
     }
 }
 
-
-void vLaunch(void)
+void
+vLaunch(void)
 {
     TaskHandle_t disttask;
-    xTaskCreate(distance_task, "TestDistThread", configMINIMAL_STACK_SIZE, NULL, 1, &disttask);
+    xTaskCreate(distance_task,
+                "TestDistThread",
+                configMINIMAL_STACK_SIZE,
+                NULL,
+                1,
+                &disttask);
 
     // Start the tasks and timer running.
     //
     vTaskStartScheduler();
 }
 
-int main(void)
+int
+main(void)
 {
     stdio_init_all();
     init_ultrasonic();
+    sleep_ms(3000);
     vLaunch();
 
     return 0;

frtos/ultrasonic_sensor/ultrasonic_sensor.h

@@ -0,0 +1,49 @@
+/**
+ * @file ultrasonic_sensor.h
+ * @brief Monitor the distance between the car and the wall
+ * @author Poon Xiang Yuan
+ */
+
+#ifndef ULTRASONIC_SENSOR_H
+#define ULTRASONIC_SENSOR_H
+
+#include "ultrasonic_init.h"
+
+void distance_task(__unused void *params)
+{
+    while (true)
+    {
+        vTaskDelay(500);
+
+        // Trigger the ultrasonic sensor
+        gpio_put(TRIG_PIN, 1);
+        sleep_us(10); // Keep the trigger on for 10 microseconds
+        gpio_put(TRIG_PIN, 0);
+
+        // Wait for the echo pulse to start
+        while (gpio_get(ECHO_PIN) == 0)
+            tight_loop_contents();
+
+        // Measure the pulse width (time taken for the echo to return)
+        uint32_t start_time = time_us_32();
+        while (gpio_get(ECHO_PIN) == 1)
+            tight_loop_contents();
+        uint32_t end_time = time_us_32();
+
+        // Calculate the distance (in centimeters)
+        uint32_t pulse_duration = end_time - start_time;
+        float distance = pulse_duration * 0.017; // Speed of sound at ~343 m/s
+
+        printf("Distance: %.2f cm\n", distance);
+
+        // If gonna bang wall
+        //
+        if (distance < 5)
+        {
+            printf("Collision Imminent!\n");
+            // Proc stop
+            //
+        }
+    }
+}
+#endif /* ULTRASONIC_SENSOR_H */