Diff: main.cpp

Revision:

1:1de97b1145f3

Parent:

0:1f9fae46bbe1

Child:

2:e98c07709d60

--- a/main.cpp	Fri Aug 11 16:20:22 2017 +0000
+++ b/main.cpp	Wed Aug 16 13:51:57 2017 +0000
@@ -1,29 +1,94 @@
 #include "mbed.h"
- 
-// Read temperature from LM75BD
+
+// Read temperature from MAX1363 3-channel ADC
+
+I2C i2c(PB_9 , PB_8);
+
+Serial pc(SERIAL_TX, SERIAL_RX);
+
+// address information for the Serenity temperature sensor device
+const int SLAVE_ADDRESS = 0x34 << 1;
+
+// MAX1363 registers
+const unsigned char MAX1363_CONFIG_REG = 0x03;  // single-ended inputs, read CH0-CH1 only
+const unsigned char MAX1363_SETUP_REG  = 0xF2;  // AIN3=output, INT REF always on
+
+// MAX1363 high byte format (byte 2 is D7-D0)
+const unsigned char MAX1363_VALID_MASK = 0x90;      // HIGH bit and 12/10 bit should always be 1
+const unsigned char MAX1363_HIGH_DATA_MASK = 0x0F;
+
+// channel address (0-3) is in CH1/CH0 (bits 5/6)
+const unsigned char MAX1363_CHANNEL_MASK = 0x60;
+const unsigned char MAX1363_CHANNEL_SHIFT = 5;
 
-I2C i2c(PB_9 , PB_8 ); 
+/** conversion factors */
+const float CONV_COEFF_A3 = 4.39403;
+const float CONV_COEFF_A2 = -11.15;
+const float CONV_COEFF_A1 = 36.4955;
+const float CONV_COEFF_A0 = 266.909;
+
+const int CONV_N = 12;
+const float CONV_VREF = 2.048;
+
+const float CONV_K_TO_C = -272.15;
 
-Serial pc (SERIAL_TX, SERIAL_RX);
-
-const int addr7bit = 0x48;      // 7 bit I2C address
-const int addr8bit = 0x48 << 1; // 8bit I2C address, 0x90
+float AdcToC(unsigned int _adc)
+{
+    float d = CONV_VREF * _adc / (1L << CONV_N);
+    float d2 = d*d;
+    float d3 = d2*d;
+    float temp_k = (CONV_COEFF_A3 * d3) +
+        (CONV_COEFF_A2 * d2) +
+        (CONV_COEFF_A1 * d) +
+        CONV_COEFF_A0;
+    return temp_k + CONV_K_TO_C;
+}
 
 int main() {
     pc.baud(250000);
-    char cmd[2];
+
+    // reserve 4 bytes for transfer
+    char cmd[4];
+
+    // initialize the adc device
+    cmd[0] = MAX1363_CONFIG_REG;
+    cmd[1] = MAX1363_SETUP_REG;
+    i2c.write(SLAVE_ADDRESS, cmd, 2);
+
+    // holds raw adc values as we convert them
+    unsigned int adc[2] = {0};
+    float values[2] = {0};
+
     while (1) {
-        cmd[0] = 0x01;
-        cmd[1] = 0x00;
-        i2c.write(addr8bit, cmd, 2);
- 
         wait(0.5);
- 
+
+        // clear buffer, only to detect invalid data
         cmd[0] = 0x00;
-        i2c.write(addr8bit, cmd, 1);
-        i2c.read( addr8bit, cmd, 2);
- 
-        float tmp = (float((cmd[0]<<8)|cmd[1]) / 256.0);
-        printf("Temp = %.2f\r\n", tmp);
+        cmd[1] = 0x00;
+        cmd[2] = 0x00;
+        cmd[3] = 0x00;
+
+        // read 4 bytes from
+        i2c.read(SLAVE_ADDRESS, cmd, 4);
+
+        for (int i=0; i<4; i+=2) {
+            // first 4 bits contain expected bits and channel id
+            if ((cmd[i] & MAX1363_VALID_MASK) == MAX1363_VALID_MASK) {
+                unsigned char ch = ((cmd[i] & MAX1363_CHANNEL_MASK) >> MAX1363_CHANNEL_SHIFT);
+                adc[ch] = ((int)(cmd[i] & MAX1363_HIGH_DATA_MASK) << 8) | cmd[i+1];
+                values[ch] = AdcToC(adc[ch]);
+            } else {
+                // handle invalid data
+            }
+        }
+
+        // output temperature data
+        
+        printf("%0.2f\t %0.2f\r\n", values[0], values[1]);
     }
-}
\ No newline at end of file
+}
+
+
+
+
+