Fork the MAX31855 library. Allows a fxn to be called to select and unselect the TC. Now using a shift register array we can multiplex a great number of these TC chips!

Dependents:   elixys

Fork of MAX31855 by Joe Staton

Files at this revision

API Documentation at this revision

Comitter:
henryeherman
Date:
Wed Oct 30 07:05:34 2013 +0000
Parent:
1:5eeee89cb281
Commit message:
Fork the MAX31855 library and allow functions to be called before reading the TC values, instead of a digital pin. Allows a shift register to be used to select the TC and a VERY large number of TC can be multiplexed!

Changed in this revision

max31855.cpp Show annotated file Show diff for this revision Revisions of this file
max31855.h Show annotated file Show diff for this revision Revisions of this file
diff -r 5eeee89cb281 -r b978f1503c27 max31855.cpp
--- a/max31855.cpp	Tue Oct 23 10:51:21 2012 +0000
+++ b/max31855.cpp	Wed Oct 30 07:05:34 2013 +0000
@@ -2,8 +2,10 @@
 #include <mbed.h>
 #include "max31855.h"
 
-max31855::max31855(SPI& _spi, PinName _ncs) : spi(_spi), ncs(_ncs) {
-
+max31855::max31855(SPI& _spi, void(*sel)(void), void(*usel)(void)) : spi(_spi) {
+    selectfxn = sel;
+    unselectfxn = usel;
+    initialise(0);
 }
 
 float max31855::read_temp() {
@@ -18,85 +20,67 @@
     uint8_t tempChipHigh=0;
     uint8_t tempChipLow=0;
     
-    if (pollTimer.read_ms() > 250){
-        //Set CS to initiate transfer and stop conversion
-        select();
+    select();
+
+    //Read in Probe tempeature
+    tempProbeHigh = spi.write(0);
+    tempProbeLow = spi.write(0);
+    
+    //Get the chip temperature and the fault data
+    tempChipHigh = spi.write(0);
+    tempChipLow = spi.write(0);
     
-        //Read in Probe tempeature
-        tempProbeHigh = spi.write(0);
-        tempProbeLow = spi.write(0);
+    //Set the chip temperature    
+    chipTemp = (tempChipHigh<<4 | tempChipLow>>4)*0.25;
+    
+    //Set CS to stop transfer and restart conversion
+    deselect(); 
+    
+    //Check for a fault (last bit of transfer is fault bit)
+    if ((tempProbeLow & 1)==1){
+        //Chip reports a fault, extract fault from Chip Temperature data
+        int faultType = (tempChipLow & 7);
         
-        //Get the chip temperature and the fault data
-        tempChipHigh = spi.write(0);
-        tempChipLow = spi.write(0);
-        
-        //Set the chip temperature    
-        chipTemp = (tempChipHigh<<4 | tempChipLow>>4)*0.25;
-        
-        //Set CS to stop transfer and restart conversion
-        deselect(); 
+        faultCode=faultType;
         
-        //Check for a fault (last bit of transfer is fault bit)
-        if ((tempProbeLow & 1)==1){
-            //Chip reports a fault, extract fault from Chip Temperature data
-            int faultType = (tempChipLow & 7);
-            
-            faultCode=faultType;
-            
-            return 2000+faultType;
-            /*if (faultType==1){
-                //Open circuit (no TC)
-                return 2000 + faultType;
-            }else if (faultType==2){
-                //Short to GND
-                return 2000 + faultType;
-            }else if (faultType==4){
-                //Short to VCC               
-                return 0.4;
-            }else{
-                return 0.5;
-            }*/
+        return 2000+faultType;
+        /*if (faultType==1){
+            //Open circuit (no TC)
+            return 2000 + faultType;
+        }else if (faultType==2){
+            //Short to GND
+            return 2000 + faultType;
+        }else if (faultType==4){
+            //Short to VCC               
+            return 0.4;
         }else{
-            //Integer value of temperature
-            value = (tempProbeHigh<< 6 | tempProbeLow>>2);
-    
-            //Get actual temperature (last 2 bits of integer are decimal 0.5 and 0.25)
-            temp = (value*0.25); // Multiply the value by 0.25 to get temp in C or
-                             //  * (9.0/5.0)) + 32.0;   // Convert value to F (ensure proper floats!)
-                             
-            return temp;
-        }
+            return 0.5;
+        }*/
     }else{
-        //Chip not ready for reading
-        return -1;
+        //Integer value of temperature
+        value = (tempProbeHigh<< 6 | tempProbeLow>>2);
+
+        //Get actual temperature (last 2 bits of integer are decimal 0.5 and 0.25)
+        temp = (value*0.25); // Multiply the value by 0.25 to get temp in C or
+                         //  * (9.0/5.0)) + 32.0;   // Convert value to F (ensure proper floats!)
+                         
+        return temp;
     }
 }
 
 void max31855::select() {
     //Set CS low to start transmission (interrupts conversion)
-    ncs = 0;
+    //ncs = 0;
+    selectfxn();
 }
 
 void max31855::deselect() {
     //Set CS high to stop transmission (restarts conversion)
-    ncs = 1;
-    //Reset conversion timer
-    pollTimer.reset();
+    //ncs = 1;
+    unselectfxn();    
 }
 
 void max31855::initialise(int setType) {
-    //Start the conversion timer
-    pollTimer.start();
+    //Start the conversion timer    
     faultCode=0;
-}
-
-int max31855::ready() {
-    //Check to see if conversion is complete
-    if (pollTimer.read_ms() > 250) {
-        //Conversion complete
-        return 1;
-    }else{
-        //Conversion incomplete
-        return 0;
-    }
 }
\ No newline at end of file
diff -r 5eeee89cb281 -r b978f1503c27 max31855.h
--- a/max31855.h	Tue Oct 23 10:51:21 2012 +0000
+++ b/max31855.h	Wed Oct 30 07:05:34 2013 +0000
@@ -6,16 +6,17 @@
 class max31855
 {
     SPI& spi;
-    DigitalOut ncs;
+    void(*selectfxn)(void);
+    void(*unselectfxn)(void);
+    //DigitalOut ncs;
     Timer pollTimer;
   public:
   
-    max31855(SPI& _spi, PinName _ncs);
+    max31855(SPI& _spi, void(*sel)(void), void(*usel)(void));
     void select();
     void deselect();
     void initialise(int setType=0);
-    
-    int ready();
+        
     int faultCode;
     
     float chipTemp;