Temperature Control

component tpid "A pid component for temperature control";
pin in float command;
pin in float feedback;
pin out float output;
pin in float Pgain;
pin in float Igain;
pin in float Dgain;

license "GPL-2.0+";
author "andypugh";

;;

static double prev_error;
static double integ;
double diff;
double error = command - feedback;
integ += error * Igain;
diff = (prev_error - error) * Dgain;
prev_error = error;
output = error * Pgain + integ + diff;
if (output < 0) {
    output = 0;
    integ = 0; // Might be right, might be wrong. 
}