Pid loop sample code

pid.c

@@ -0,0 +1,74 @@
+#include <math.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+#define BUFFER_SIZE 100
+
+typedef struct {
+    float Kp, Ki, Kd;                // PID gains
+    float error_buffer[BUFFER_SIZE]; // Circular buffer for integral calculation
+    int buffer_index;                // Current index in the buffer
+    float integral_sum;              // Running sum of integral terms
+    float prev_error;                // Previous error for derivative term
+    float dt;                        // Sample time (seconds)
+} PIDController;
+
+// Initialize PID controller
+void pid_init(PIDController *pid, float Kp, float Ki, float Kd, float dt) {
+    pid->Kp = Kp;
+    pid->Ki = Ki;
+    pid->Kd = Kd;
+    pid->dt = dt;
+    pid->buffer_index = 0;
+    pid->integral_sum = 0.0f;
+    pid->prev_error = 0.0f;
+    memset(pid->error_buffer, 0, sizeof(pid->error_buffer));
+}
+
+// Compute PID output
+float pid_compute(PIDController *pid, float setpoint, float pv) {
+    float error = setpoint - pv;
+
+    // Update integral term using circular buffer
+    pid->integral_sum -=
+        pid->error_buffer[pid->buffer_index]; // Remove oldest value
+    pid->error_buffer[pid->buffer_index] =
+        error * pid->dt; // Store new integral term
+    pid->integral_sum += pid->error_buffer[pid->buffer_index]; // Add new value
+
+    // Advance circular buffer index
+    pid->buffer_index = (pid->buffer_index + 1) % BUFFER_SIZE;
+
+    // Compute derivative term
+    float derivative = (error - pid->prev_error) / pid->dt;
+    pid->prev_error = error;
+
+    // Compute PID output
+    float output = (pid->Kp * error) + (pid->Ki * pid->integral_sum) +
+                   (pid->Kd * derivative);
+
+    return output;
+}
+
+int main() {
+    PIDController pid;
+    pid_init(&pid, 1.0f, 0.1f, 0.05f,
+             0.01f); // Kp, Ki, Kd, dt (10ms sample time)
+
+    float setpoint = 100.0f;
+    float pv = 90.0f;
+
+    for (int i = 0; i < 50; i++) {
+        float output = pid_compute(&pid, setpoint, pv);
+        printf("Iteration %d: Setpoint: %.2f, PV: %.2f, Output: %.2f\n", i,
+               setpoint, pv, output);
+
+        // Simulate process variable update
+        pv += output * 0.1f;
+        if (fabsf(output) < 0.4)
+            setpoint = 150;
+    }
+
+    return 0;
+}