Change temperature sensor to transmit meaningful C*256 values

nRF24 · Mar 27, 2012 · 7c76f97 · 7c76f97
1 parent 442edb2
commit 7c76f97
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Showing 2 changed files with 12 additions and 5 deletions.
diff --git a/examples/sensornet/S_message.cpp b/examples/sensornet/S_message.cpp
@@ -22,9 +22,10 @@ char S_message::buffer[32];
 
 char* S_message::toString(void)
 {
-  snprintf(buffer,sizeof(buffer),"#%06u %04x /%2u.%02uV",
+  snprintf(buffer,sizeof(buffer),"#%06u %2u.%02uC /%2u.%02uV",
       counter,
-      temp_reading,
+      temp_reading >> 8,
+      ( temp_reading & 0xFF ) * 100 / 256,
       voltage_reading >> 8,
       ( voltage_reading & 0xFF ) * 100 / 256
       );

diff --git a/examples/sensornet/sensornet.pde b/examples/sensornet/sensornet.pde
@@ -155,12 +155,18 @@ void loop(void)
 
     // Take the temp reading 
     i = num_measurements;
+    uint32_t reading = 0;
     while(i--)
-      message.temp_reading += analogRead(temp_pin); 
-
+      reading += analogRead(temp_pin);
+
+    // Convert the voltage reading to celcius*256
+    // This is the formula for MCP9700.
+    // C = ( V - 1/2 ) / 100
+    message.temp_reading = ( reading - 0x8000 ) * 0x100 / ( 0x10000 / 100 );
+
     // Take the voltage reading 
     i = num_measurements;
-    uint32_t reading = 0;
+    reading = 0;
     while(i--)
       reading += analogRead(voltage_pin);