1 void pid_update(pid_type* pid){
   2     pid->error = pid->in - pid->ref;
   3     pid->proportional = pid->Kp * (pid->error - pid->error_old1);
   4     pid->integral = pid->Ki * pid->error;
   5     pid->derivative = pid->Kd * (pid->in - 2*pid->in_old1 + pid->in_old2);
   6 
   7     if(pid->in >= 5 || pid->in <= -5){
   8         pid->integral = 0.1 * pid->integral;
   9     }
  10     pid->out = pid->out_old + pid->proportional + pid->derivative + pid->integral;
  11     pid->in_old2 = pid->in_old1;
  12     pid->in_old1 = pid->in;
  13     pid->error_old1 = pid->error;
  14     pid->out_old = pid->out;
  15 }