Fix #25, Combine error and t into error code.

Author: winlinvip

SimpleDHT.cpp

@@ -215,13 +215,13 @@ int SimpleDHT11::sample(byte data[40]) {
     //    1. PULL LOW 80us
     //    2. PULL HIGH 80us
     long t = levelTime(LOW);          // 1.
-    if (t < 36) {                    // specs [2]: 80us
-        return SimpleDHTErrStartLow;
+    if (t < 30) {                    // specs [2]: 80us
+        return simpleDHTCombileError(t, SimpleDHTErrStartLow);
     }
 
     t = levelTime(HIGH);             // 2.
-    if (t < 68) {                    // specs [2]: 80us
-        return SimpleDHTErrStartHigh;
+    if (t < 50) {                    // specs [2]: 80us
+        return simpleDHTCombileError(t, SimpleDHTErrStartHigh);
     }
 
     // DHT11 data transmite:
@@ -232,13 +232,13 @@ int SimpleDHT11::sample(byte data[40]) {
     for (int j = 0; j < 40; j++) {
           t = levelTime(LOW);          // 1.
           if (t < 24) {                    // specs says: 50us
-              return SimpleDHTErrDataLow;
+              return simpleDHTCombileError(t, SimpleDHTErrDataLow);
           }
 
           // read a bit
           t = levelTime(HIGH);              // 2.
           if (t < 11) {                     // specs say: 20us
-              return SimpleDHTErrDataRead;
+              return simpleDHTCombileError(t, SimpleDHTErrDataRead);
           }
           data[ j ] = (t > 40 ? 1 : 0);     // specs: 26-28us -> 0, 70us -> 1
     }
@@ -247,7 +247,7 @@ int SimpleDHT11::sample(byte data[40]) {
     //    1. PULL LOW 50us.
     t = levelTime(LOW);                     // 1.
     if (t < 24) {                           // specs say: 50us
-        return SimpleDHTErrDataEOF;
+        return simpleDHTCombileError(t, SimpleDHTErrDataEOF);
     }
 
     return SimpleDHTErrSuccess;
@@ -319,10 +319,10 @@ int SimpleDHT22::sample(byte data[40]) {
     //    2. T(reh), PULL HIGH 80us(75-85us).
     long t = 0;
     if ((t = levelTime(LOW)) < 30) {
-        return SimpleDHTErrStartLow;
+        return simpleDHTCombileError(t, SimpleDHTErrStartLow);
     }
     if ((t = levelTime(HIGH)) < 50) {
-        return SimpleDHTErrStartHigh;
+        return simpleDHTCombileError(t, SimpleDHTErrStartHigh);
     }
 
     // DHT11 data transmite:
@@ -332,13 +332,13 @@ int SimpleDHT22::sample(byte data[40]) {
     for (int j = 0; j < 40; j++) {
           t = levelTime(LOW);          // 1.
           if (t < 24) {                    // specs says: 50us
-              return SimpleDHTErrDataLow;
+              return simpleDHTCombileError(t, SimpleDHTErrDataLow);
           }
 
           // read a bit
           t = levelTime(HIGH);              // 2.
           if (t < 11) {                     // specs say: 26us
-              return SimpleDHTErrDataRead;
+              return simpleDHTCombileError(t, SimpleDHTErrDataRead);
           }
           data[ j ] = (t > 40 ? 1 : 0);     // specs: 22-30us -> 0, 70us -> 1
     }
@@ -347,7 +347,7 @@ int SimpleDHT22::sample(byte data[40]) {
     //    1. T(en), PULL LOW 50us(45-55us).
     t = levelTime(LOW);
     if (t < 24) {
-        return SimpleDHTErrDataEOF;
+        return simpleDHTCombileError(t, SimpleDHTErrDataEOF);
     }
 
     return SimpleDHTErrSuccess;

SimpleDHT.h

@@ -27,24 +27,31 @@
 
 #include <Arduino.h>
 
+// High 8bits are time duration.
+// Low 8bits are error code.
+// For example, 0x0310 means t=0x03 and code=0x10,
+// which is start low signal(0x10) error.
+// @see https://github.com/winlinvip/SimpleDHT/issues/25
+#define simpleDHTCombileError(t, err) ((t << 8) & 0xff00) | (err & 0x00ff)
+
 // Success.
 #define SimpleDHTErrSuccess 0
 // Error to wait for start low signal.
-#define SimpleDHTErrStartLow 100
+#define SimpleDHTErrStartLow 0x10
 // Error to wait for start high signal.
-#define SimpleDHTErrStartHigh 101
+#define SimpleDHTErrStartHigh 0x11
 // Error to wait for data start low signal.
-#define SimpleDHTErrDataLow 102
+#define SimpleDHTErrDataLow 0x12
 // Error to wait for data read signal.
-#define SimpleDHTErrDataRead 103
+#define SimpleDHTErrDataRead 0x13
 // Error to wait for data EOF signal.
-#define SimpleDHTErrDataEOF 104
+#define SimpleDHTErrDataEOF 0x14
 // Error to validate the checksum.
-#define SimpleDHTErrDataChecksum 105
+#define SimpleDHTErrDataChecksum 0x15
 // Error when temperature and humidity are zero, it shouldn't happen.
-#define SimpleDHTErrZeroSamples 106
+#define SimpleDHTErrZeroSamples 0x16
 // Error when pin is not initialized.
-#define SimpleDHTErrNoPin 107
+#define SimpleDHTErrNoPin 0x17
 
 class SimpleDHT {
 protected: