Diff: main.cpp

Revision:

1:404c34e19f93

Parent:

0:41f53df528da

--- a/main.cpp	Fri Feb 21 13:02:09 2014 +0000
+++ b/main.cpp	Mon Mar 02 20:12:10 2015 +0000
@@ -1,8 +1,10 @@
 #include "mbed.h"
- 
-#define LM75_REG_TEMP (0x00) // Temperature Register
-#define LM75_REG_CONF (0x01) // Configuration Register
-#define LM75_ADDR     (0x90) // LM75 address
+#include "I2C.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(I2C_SDA, I2C_SCL);
  
@@ -10,59 +12,91 @@
  
 Serial pc(SERIAL_TX, SERIAL_RX);
  
-volatile char TempCelsiusDisplay[] = "+abc.d C";
+volatile char TempCelsiusDisplay[] = "+abc.dd C";
  
 int main()
 {
  
-    char data_write[2];
+    char data_write[3];
     char data_read[2];
- 
-    /* Configure the Temperature sensor device STLM75:
-    - Thermostat mode Interrupt
+    int tempval;
+    
+    wait(3);
+    pc.printf("PumpHouse mcp9808 test! March 2, 2015  1450\n\r");
+    i2c.frequency(10000); // default is 100000
+    
+    /* Configure the Temperature sensor device MCP9808:
+    - Thermostat mode Interrupt not used
     - Fault tolerance: 0
     */
-    data_write[0] = LM75_REG_CONF;
-    data_write[1] = 0x02;
-    int status = i2c.write(LM75_ADDR, data_write, 2, 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);
         }
     }
  
+    pc.printf("enter forever loop\r\n");
     while (1) {
         // Read temperature register
-        data_write[0] = LM75_REG_TEMP;
-        i2c.write(LM75_ADDR, data_write, 1, 1); // no stop
-        i2c.read(LM75_ADDR, data_read, 2, 0);
+        data_write[0] = MCP9808_REG_TEMP;
+        i2c.write(MCP9808_ADDR, data_write, 1, 1); // no stop
+        i2c.read(MCP9808_ADDR, data_read, 2, 0);
  
-        // Calculate temperature value in Celcius
-        int tempval = (int)((int)data_read[0] << 8) | data_read[1];
-        tempval >>= 7;
-        if (tempval <= 256) {
+ // check Ta vs Tcrit
+        if((data_read[0] & 0x80)  == 0x80) {
+            pc.printf(" temp >= critical ");
+        }
+        if((data_read[0] & 0x40) == 0x40) {
+            pc.printf("   temp > upper limit ");
+        }
+        if((data_read[0] & 0x20) == 0x20) {
+            pc.printf(" temp < lower limit  ");
+        }
+        if(data_read[0] & 0xE0) {
+            pc.printf("\r\n");   
+            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] = '+';
-        } else {
-            TempCelsiusDisplay[0] = '-';
-            tempval = 512 - tempval;
+            tempval = (data_read[0] << 4) + (data_read[1] >> 4);
         }
  
-        // Decimal part (0.5°C precision)
-        if (tempval & 0x01) {
-            TempCelsiusDisplay[5] = 0x05 + 0x30;
+        // 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 {
-            TempCelsiusDisplay[5] = 0x00 + 0x30;
+            if(data_read[1] & 0x04) {
+                TempCelsiusDisplay[5] = '2';
+                TempCelsiusDisplay[6] = '5';
+            }else{
+                TempCelsiusDisplay[5] = '0';
+                TempCelsiusDisplay[6] = '0';
+            }
         }
  
         // Integer part
-        tempval >>= 1;
         TempCelsiusDisplay[1] = (tempval / 100) + 0x30;
         TempCelsiusDisplay[2] = ((tempval % 100) / 10) + 0x30;
         TempCelsiusDisplay[3] = ((tempval % 100) % 10) + 0x30;
  
         // Display result
-        pc.printf("temp = %s\n", TempCelsiusDisplay);
+        pc.printf("temp = %s\r\n", TempCelsiusDisplay);
         myled = !myled;
         wait(1.0);
     }