Hugo Harming / Mbed 2 deprecated Lots_of_DS18B20

// Demo on how to identify and read multiple DS18B20 connected to the same bus. // Parasitic power is not used in this example. // This program is based on the sample code from Maxim/Dallas application // note 162 (http://www.maxim-ic.com/app-notes/index.mvp/id/162). Program output should look like this: *** Test with multiple DS18B20 *** Memory allocated for 20 devices. Scanning for devices... ROM CODE =62:00:00:01:CB:25:CA:28 1 ROM CODE =B6:00:00:01:CB:1B:9E:28 2 ROM CODE =66:00:00:01:CB:28:59:28 3 3 devices found. Scanning completed. Temp: 022.6875 Device: 000001CB25CA 001 Temp: 022.6875 Device: 000001CB1B9E 002 Temp: 027.6250 Device: 000001CB2859 003 Temp: 022.6250 Device: 000001CB25CA 001 Temp: 022.6875 Device: 000001CB1B9E 002 Temp: 025.3125 Device: 000001CB2859 003 Temp: 022.8125 Device: 000001CB25CA 001 Temp: 024.1875 Device: 000001CB1B9E 002 Temp: 023.7500 Device: 000001CB2859 003

Dependencies:   mbed

Diff: main.cpp

Revision:
4:6ade7fcb2925
Parent:
3:28b7b7fddede
Child:
7:cf5affdab535
--- a/main.cpp	Mon Jan 23 10:13:57 2012 +0000
+++ b/main.cpp	Thu Jan 28 09:05:50 2016 +0000
@@ -7,6 +7,31 @@
 // note 162 (http://www.maxim-ic.com/app-notes/index.mvp/id/162).
 //////////////////////////////////////////////////////////////////////////////
 //////////////////////////////////////////////////////////////////////////////
+// Program output should look like this:
+// *** Test with multiple DS18B20 ***
+// Memory allocated for 20 devices.
+// Scanning for devices...
+// ROM CODE =62:00:00:01:CB:25:CA:28 1
+// ROM CODE =B6:00:00:01:CB:1B:9E:28 2
+// ROM CODE =66:00:00:01:CB:28:59:28 3
+// 3 devices found. Scanning completed.
+// Temp: 022.6875 Device: 000001CB25CA 001
+// Temp: 022.6875 Device: 000001CB1B9E 002
+// Temp: 027.6250 Device: 000001CB2859 003
+// Temp: 022.6250 Device: 000001CB25CA 001
+// Temp: 022.6875 Device: 000001CB1B9E 002
+// Temp: 025.3125 Device: 000001CB2859 003
+// Temp: 022.8125 Device: 000001CB25CA 001
+// Temp: 024.1875 Device: 000001CB1B9E 002
+// Temp: 023.7500 Device: 000001CB2859 003
+//////////////////////////////////////////////////////////////////////////////
+//////////////////////////////////////////////////////////////////////////////
+// I have found that adding a small capacitor (100 nF or so) over the supply
+// lines on long cable runs significantly reduces the number of bad readings.
+// If you make temperature conversions more often than every 4-5 seconds, the
+// device(s) will self heat and produce a higher temperature reading.
+//////////////////////////////////////////////////////////////////////////////
+//////////////////////////////////////////////////////////////////////////////
 
 #include <mbed.h>
 Serial pc(USBTX, USBRX);
@@ -15,7 +40,7 @@
 #define TRUE 1
 #define MaxROMs 20 // Defines how many devices space is allocated for.
 
-DigitalInOut DQ(p30);
+DigitalInOut DQ(p30); // Attach the DQ pin of your sensors to this mbed pin.
 
 unsigned char SPad[9]; // Scratchpad storage
 unsigned char ROM[8];
@@ -53,7 +78,7 @@
     wait_us(70); // wait for presence
     presence = DQ; // get presence signal
     wait_us(410); // wait for end of timeslot
-    return(presence); // presence signal returned, 0=presence, 1 = no part
+    return(presence); // presence signal returned, 0=presence, 1 = no sensor found.
 }
 
 //////////////////////////////////////////////////////////////////////////////
@@ -101,7 +126,7 @@
     for (i=0; i<8; i++) {// writes byte, one bit at a time
         temp = val>>i; // shifts val right 'i' spaces
         temp &= 0x01; // copy that bit to temp
-        write_bit(temp); // write bit in temp into
+        write_bit(temp); // write bit
     }
 }
 
@@ -125,7 +150,7 @@
     unsigned char g; // Output bit
     unsigned char nxt; // return value
     int flag;
-    nxt = FALSE; // set the next flag to false
+    nxt = FALSE; // set the nxt flag to false
     dowcrc = 0; // reset the dowcrc
     flag = ow_reset(); // reset the 1-Wire
     if(flag||doneFlag) { // no parts -> return false