Diff: temp_sensor.cpp

Revision:

3:c611fff05072

diff -r 146625d6992d -r c611fff05072 temp_sensor.cpp
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/temp_sensor.cpp	Tue Mar 15 17:52:05 2016 +0000
@@ -0,0 +1,83 @@
+#include "temp_sensor.h"
+
+/* MCP9808 high accuracy temp sensor from adafruit (no address pins pulled up) */ 
+#define MCP9808_REG_TEMP (0x05) // Temperature Register
+#define MCP9808_REG_CONF (0x01) // Configuration Register
+#define MCP9808_ADDR     (0x30) // MCP9808 base address 0x18<<1
+ 
+I2C i2c(PTE25, PTE24);
+
+char data_write[3];
+char data_read[2];
+int tempval;
+
+volatile char TempCelsiusDisplay[] = "+abc.dd C";
+
+void init_temp_sensor() {
+    
+    wait(3);
+    i2c.frequency(10000); // default is 100000
+    
+    /* Configure the Temperature sensor device MCP9808:
+    - Thermostat mode Interrupt not used
+    - Fault tolerance: 0
+    */
+    data_write[0] = MCP9808_REG_CONF;
+    data_write[1] = 0x00;  // config msb
+    data_write[2] = 0x00;  // config lsb
+    int status = i2c.write(MCP9808_ADDR, data_write, 3, 0);
+    if (status != 0) { // Error
+//        pc.printf("  error status = 0x%08x\r\n", status);
+//        while (1) {
+//            myled = !myled;
+//            wait(0.2);
+//        }
+    }
+    
+}
+
+void check_temp() {
+    // Read temperature register
+    data_write[0] = MCP9808_REG_TEMP;
+    i2c.write(MCP9808_ADDR, data_write, 1, 1); // no stop
+    i2c.read(MCP9808_ADDR, data_read, 2, 0);
+
+    if(data_read[0] & 0xE0) {
+        data_read[0] = data_read[0] & 0x1F;  // clear flag bits
+    }
+    if((data_read[0] & 0x10) == 0x10) { 
+        data_read[0] = data_read[0] & 0x0F;
+        TempCelsiusDisplay[0] = '-';
+        tempval = 256 - (data_read[0] << 4) + (data_read[1] >> 4);
+    } else {
+        TempCelsiusDisplay[0] = '+';
+        tempval = (data_read[0] << 4) + (data_read[1] >> 4);
+    }
+
+    // fractional part (0.25°C precision)
+    if (data_read[1] & 0x08) {
+        if(data_read[1] & 0x04) {
+            TempCelsiusDisplay[5] = '7';
+            TempCelsiusDisplay[6] = '5';
+        } else {
+            TempCelsiusDisplay[5] = '5';
+            TempCelsiusDisplay[6] = '0';
+        }
+    } else {
+        if(data_read[1] & 0x04) {
+            TempCelsiusDisplay[5] = '2';
+            TempCelsiusDisplay[6] = '5';
+        }else{
+            TempCelsiusDisplay[5] = '0';
+            TempCelsiusDisplay[6] = '0';
+        }
+    }
+
+    // Integer part
+    TempCelsiusDisplay[1] = (tempval / 100) + 0x30;
+    TempCelsiusDisplay[2] = ((tempval % 100) / 10) + 0x30;
+    TempCelsiusDisplay[3] = ((tempval % 100) % 10) + 0x30;
+}
+
+
+