Diff: MAX31855.cpp

Revision:

0:5d56064bc4c3

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/MAX31855.cpp	Mon Feb 09 05:56:04 2015 +0000
@@ -0,0 +1,91 @@
+/*    
+ * A library for MAX31855 
+ *   
+ * Copyright (c) 2015 Seeed Technology Limited.  
+ * Author      : Yihui Xiong
+ *
+ * The MIT License (MIT)
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ * 
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ * 
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+
+
+#include "max31855.h"
+
+#define LOG(args...)    printf(args)
+
+MAX31855::MAX31855(SPI& _spi, PinName _ncs) : spi(_spi), ncs(_ncs)
+{
+    thermocoupleT = 0.0 / 0.0;
+    internalT     = 0.0 / 0.0;
+    lastReadTime = 0;
+}
+
+float MAX31855::read(temperature_type_t type) {
+    uint8_t buf[4];
+    
+    uint32_t time = us_ticker_read();
+    uint32_t duration = time - lastReadTime;
+    if (duration > 250000) {   // more than 250ms
+        //Set CS low to start transmission (interrupts conversion)
+        ncs = 0;
+    
+        //Read in Probe tempeature
+        for (int i = 0; i < 4; i++) {
+            buf[i] = spi.write(0);
+        }
+        
+        //Set CS high to stop transmission (restarts conversion)
+        ncs = 1;
+        
+        if (buf[1] & 1) {
+            uint8_t fault = buf[3] & 0x7;
+            if (fault & 0x1) {
+                LOG("The thermocouple is open (no connections).\r\n"); 
+            }
+            if (fault & 0x2) {
+                LOG("The thermocouple is short-circuited to GND.\r\n"); 
+            }
+            if (fault & 0x4) {
+                LOG("The thermocouple is short-circuited to VCC.\r\n"); 
+            }
+            return 0.0 / 0.0;
+        }
+        
+        int t1 = ((buf[0] & 0x7F) << 6) + (buf[1] >> 2);
+        if (buf[0] & 0x80) {            // sign bit
+            t1 = -t1;
+        }
+        thermocoupleT = t1 * 0.25;
+        
+        int t2 = ((buf[2] & 0x7F) << 4) + (buf[3] >> 4);
+        if (buf[2] & 0x80) {
+            t2 = -t2;
+        }
+        internalT = t2 * 0.0625;
+    }
+    
+    if (THERMOCOUPLE_T == type) {
+        return thermocoupleT;
+    } else {
+        return internalT;
+    }
+}
+
+