Merge pull request #289 from Laxilef/fix_85c

Detect power on reset and insufficient power for DS18B20

Author: milesburton

DallasTemperature.cpp

@@ -558,6 +558,15 @@ int32_t DallasTemperature::calculateTemperature(const uint8_t* deviceAddress, ui
                        | neg;
     }
 
+    // detect POR and insufficient power conditions
+    if (deviceAddress[DSROM_FAMILY] == DS18B20MODEL) {
+        if (scratchPad[0] == 0x50 && scratchPad[1] == 0x05 && scratchPad[6] == 0x0C) {
+            return DEVICE_POWER_ON_RESET_RAW;
+        } else if (scratchPad[0] == 0xFF && scratchPad[1] == 0x07) {
+            return DEVICE_INSUFFICIENT_POWER_RAW;
+        }
+    }
+
   /*
    DS1820 and DS18S20 have a 9-bit temperature register.
 

DallasTemperature.h

@@ -46,6 +46,14 @@
 #define DEVICE_FAULT_SHORTVDD_F -421.599976
 #define DEVICE_FAULT_SHORTVDD_RAW -32256
 
+#define DEVICE_POWER_ON_RESET_C -251
+#define DEVICE_POWER_ON_RESET_F -419.799988
+#define DEVICE_POWER_ON_RESET_RAW -32128
+
+#define DEVICE_INSUFFICIENT_POWER_C -250
+#define DEVICE_INSUFFICIENT_POWER_F -418.0
+#define DEVICE_INSUFFICIENT_POWER_RAW -32000
+
 // Configuration Constants
 #define MAX_CONVERSION_TIMEOUT 750
 #define MAX_INITIALIZATION_RETRIES 3

keywords.txt

@@ -85,3 +85,9 @@ DEVICE_FAULT_SHORTGND_RAW	LITERAL1
 DEVICE_FAULT_SHORTVDD_C	LITERAL1
 DEVICE_FAULT_SHORTVDD_F	LITERAL1
 DEVICE_FAULT_SHORTVDD_RAW	LITERAL1
+DEVICE_POWER_ON_RESET_C	LITERAL1
+DEVICE_POWER_ON_RESET_F	LITERAL1
+DEVICE_POWER_ON_RESET_RAW	LITERAL1
+DEVICE_INSUFFICIENT_POWER_C	LITERAL1
+DEVICE_INSUFFICIENT_POWER_F	LITERAL1
+DEVICE_INSUFFICIENT_POWER_RAW	LITERAL1

test/unit_test_001.cpp

@@ -47,6 +47,14 @@ unittest(test_error_code) {
     assertEqual(DEVICE_FAULT_SHORTVDD_C, -252);
     assertEqualFloat(DEVICE_FAULT_SHORTVDD_F, -421.6, 0.1);
     assertEqual(DEVICE_FAULT_SHORTVDD_RAW, -32256);
+
+    assertEqual(DEVICE_POWER_ON_RESET_C, -251);
+    assertEqualFloat(DEVICE_POWER_ON_RESET_F, -419.8, 0.1);
+    assertEqual(DEVICE_POWER_ON_RESET_RAW, -32128);
+
+    assertEqual(DEVICE_INSUFFICIENT_POWER_C, -250);
+    assertEqualFloat(DEVICE_INSUFFICIENT_POWER_F, -418.0, 0.1);
+    assertEqual(DEVICE_INSUFFICIENT_POWER_RAW, -32000);
 }
 
 // Test basic initialization and functionality of the DallasTemperature library