diff -r 198f3b4bd0d8 -r 73cd31dc6ce1 thermferm/pid.c
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/thermferm/pid.c	Thu Feb 19 14:42:55 2015 +0100
@@ -0,0 +1,50 @@
+/*****************************************************************************
+ * Copyright (C) 2015
+ *   
+ * Michiel Broek <mbroek at mbse dot eu>
+ *
+ * This file is part of the mbsePi-apps
+ *
+ * This is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License as published by the
+ * Free Software Foundation; either version 2, or (at your option) any
+ * later version.
+ *
+ * mbsePi-apps is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ * 
+ * You should have received a copy of the GNU General Public License
+ * along with ThermFerm; see the file COPYING.  If not, write to the Free
+ * Software Foundation, 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA.
+ *****************************************************************************/
+
+#include "thermferm.h"
+#include "pid.h"
+
+
+double UpdatePID(pid_var *pid, double error, double position)
+{
+    double	pTerm, dTerm, iTerm;
+
+    pTerm = pid->pGain * error;
+
+    /*
+     * Calculate the integral state with appopriate limiting
+     */
+    pid->iState += error;
+    if (pid->iState > pid->iMax)
+	pid->iState = pid->iMax;
+    else if (pid->iState < pid->iMin)
+	pid->iState = pid->iMin;
+
+    iTerm = pid->iGain * pid->iState;
+
+    dTerm = pid->dGain * (pid->dState - position);
+    pid->dState = position;
+
+    return pTerm + dTerm + iTerm;
+}
+
+