From 93ced92dc774482a60a9774db81ca9585e5506b4 Mon Sep 17 00:00:00 2001
From: Michael Wiebusch <m.wiebusch@gsi.de>
Date: Thu, 16 Apr 2015 15:02:52 +0200
Subject: [PATCH] adapted PID constants to new CPU cooler and fixed the PID
 overflow bug

---
 atmega32u4/cooler/cooler.c | 43 ++++++++++++++++++++------------------
 1 file changed, 23 insertions(+), 20 deletions(-)

diff --git a/atmega32u4/cooler/cooler.c b/atmega32u4/cooler/cooler.c
index 635f52e..72f4770 100644
--- a/atmega32u4/cooler/cooler.c
+++ b/atmega32u4/cooler/cooler.c
@@ -3,7 +3,7 @@
 #include "main.h"
 
 #define SET_VAL_UPPER  30*16 //upper limit to set value
-#define SET_VAL_LOWER -10*16 //lower limit to set value
+#define SET_VAL_LOWER -20*16 //lower limit to set value
 
 #define MAX(x,y)               (((x) > (y)) ? (x) : (y))
 #define MIN(x,y)               (((x) < (y)) ? (x) : (y)) 
@@ -349,37 +349,39 @@ void new_set_value(int16_t value){
 // all constants in x/10
 #define PID_CONST_PROP         800
 #define PID_CONST_INT          15
-#define PID_CONST_DIFF         0
+#define PID_CONST_DIFF         1600
 #define PID_ACTOR_OUTPUT_LIMIT 1023
 #define PID_INTEGRAL_LIMIT     600
 #define PID_FINE_INTERVAL      2*16 // within 2 degrees
 
 uint16_t pid_calculation(int16_t error) {
-  static int16_t intg_error     = 0;
+  static int16_t intg_error   = 0;
   static int16_t last_error   = 0;
-  int16_t diff_error = error-last_error;
+  int16_t        diff_error   = error-last_error;
   
-  if( abs(error)<PID_FINE_INTERVAL ) { // use integral only inside a fine interval
+  if( abs(error)<PID_FINE_INTERVAL ) { // use integral/differential only inside a fine interval
     intg_error += error;
-    intg_error = MAX(-PID_INTEGRAL_LIMIT,intg_error);
-    intg_error = MIN(PID_INTEGRAL_LIMIT,intg_error);
-  } 
-  
-  int32_t actor = 
-      ((intg_error * PID_CONST_INT )/10)
-    + ((diff_error * PID_CONST_DIFF)/10)
-    + ((error      * PID_CONST_PROP)/10);
+    intg_error  = MAX(-PID_INTEGRAL_LIMIT,intg_error);
+    intg_error  = MIN( PID_INTEGRAL_LIMIT,intg_error);
+  } else {
+    diff_error  = 0;
+  }
+  
+  int32_t actuator = 
+      (( ((int32_t) intg_error) * PID_CONST_INT )/10)
+    + (( ((int32_t) diff_error) * PID_CONST_DIFF)/10)
+    + (( ((int32_t) error     ) * PID_CONST_PROP)/10);
   // allow only positive values;
-  actor = MAX(0,actor);
+  actuator = MAX(0,actuator);
   // output is limited
-  actor = MIN(PID_ACTOR_OUTPUT_LIMIT,actor);
+  actuator = MIN(PID_ACTOR_OUTPUT_LIMIT,actuator);
   last_error = error;
   
 //   //for debug
 //   uart_puts("integral: ");
 //   uart_print_signed_number(intg_error,6);
 //   uart_puts("\n\r");
-  return actor;
+  return actuator;
 }
 
 void showPower(void){
@@ -401,28 +403,28 @@ void showPower(void){
 
 
 void uartReport(void){
-  uart_puts("Setpoint: ");
+  uart_puts("Setpoint:     ");
   uart_print_sign(set_value);
   uart_print_number(abs(set_value)/16,2);
   usb_serial_putchar('.');
   usb_serial_putchar('0'+lut[abs(set_value)%16]); // print post comma
   uart_puts(" deg C\n\r");
   
-  uart_puts("Temperature: ");
+  uart_puts("Temperature:  ");
   uart_print_sign(temps[MAINSENSOR]);
   uart_print_number(abs(temps[MAINSENSOR])/16,2);
   usb_serial_putchar('.');
   usb_serial_putchar('0'+lut[abs(temps[MAINSENSOR])%16]); // print post comma
   uart_puts(" deg C\n\r");
 
-  uart_puts("2nd temp:    ");
+  uart_puts("2nd temp:     ");
   uart_print_sign(temps[SUPPSENSOR]);
   uart_print_number(abs(temps[SUPPSENSOR])/16,2);
   usb_serial_putchar('.');
   usb_serial_putchar('0'+lut[abs(temps[SUPPSENSOR])%16]); // print post comma
   uart_puts(" deg C\n\r");
 
-  uart_puts("PWM Output: ");
+  uart_puts("PWM Output:   ");
   uart_print_number(output_power_percent,3);
   uart_puts("%\n\r");
   
@@ -456,6 +458,7 @@ __attribute__((naked)) int main(void) {
   new_set_value(12*16);
   
   
+  // the main loop
   
   while (1) {    
     int n = usb_serial_getchar();
-- 
2.43.0