Revision 2:b978f1503c27, committed 2013-10-30

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

--- 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

--- 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;