diff --git a/SimpleDHT.cpp b/SimpleDHT.cpp
index 3d99cf8..fd3a6e6 100644
--- a/SimpleDHT.cpp
+++ b/SimpleDHT.cpp
@@ -24,14 +24,6 @@ SOFTWARE.
 
 #include "SimpleDHT.h"
 
-int SimpleDHT::ErrSuccess = 0;
-int SimpleDHT::ErrStartLow = 100;
-int SimpleDHT::ErrStartHigh = 101;
-int SimpleDHT::ErrDataLow = 102;
-int SimpleDHT::ErrDataRead = 103;
-int SimpleDHT::ErrDataEOF = 104;
-int SimpleDHT::ErrDataChecksum = 105;
-
 int SimpleDHT::confirm(int pin, int us, byte level) {
     // wait one more count to ensure.
     int cnt = us / 10 + 1;
@@ -48,7 +40,7 @@ int SimpleDHT::confirm(int pin, int us, byte level) {
     if (!ok) {
         return -1;
     }
-    return ErrSuccess;
+    return SimpleDHTErrSuccess;
 }
 
 byte SimpleDHT::bits2byte(byte data[8]) {
@@ -67,24 +59,24 @@ int SimpleDHT::parse(byte data[40], byte* ptemperature, byte* phumidity) {
     byte check = bits2byte(data + 32);
     byte expect = humidity + humidity2 + temperature + temperature2;
     if (check != expect) {
-        return ErrDataChecksum;
+        return SimpleDHTErrDataChecksum;
     }
     *ptemperature = temperature;
     *phumidity = humidity;
-    return ErrSuccess;
+    return SimpleDHTErrSuccess;
 }
 
 int SimpleDHT::read(int pin, byte* ptemperature, byte* phumidity, byte pdata[40]) {
-    int ret = ErrSuccess;
+    int ret = SimpleDHTErrSuccess;
 
     byte data[40] = {0};
-    if ((ret = sample(pin, data)) != ErrSuccess) {
+    if ((ret = sample(pin, data)) != SimpleDHTErrSuccess) {
         return ret;
     }
 
     byte temperature = 0;
     byte humidity = 0;
-    if ((ret = parse(data, &temperature, &humidity)) != ErrSuccess) {
+    if ((ret = parse(data, &temperature, &humidity)) != SimpleDHTErrSuccess) {
         return ret;
     }
 
@@ -120,10 +112,10 @@ int SimpleDHT11::sample(int pin, byte data[40]) {
     //    1. PULL LOW 80us
     //    2. PULL HIGH 80us
     if (confirm(pin, 80, LOW)) {
-        return ErrStartLow;
+        return SimpleDHTErrStartLow;
     }
     if (confirm(pin, 80, HIGH)) {
-        return ErrStartHigh;
+        return SimpleDHTErrStartHigh;
     }
 
     // DHT11 data transmite:
@@ -132,7 +124,7 @@ int SimpleDHT11::sample(int pin, byte data[40]) {
     //    3. PULL HIGH 70us, bit(1)
     for (int j = 0; j < 40; j++) {
         if (confirm(pin, 50, LOW)) {
-            return ErrDataLow;
+            return SimpleDHTErrDataLow;
         }
 
         // read a bit, should never call method,
@@ -148,7 +140,7 @@ int SimpleDHT11::sample(int pin, byte data[40]) {
             delayMicroseconds(10);
         }
         if (!ok) {
-            return ErrDataRead;
+            return SimpleDHTErrDataRead;
         }
         data[j] = (tick > 3? 1:0);
     }
@@ -156,10 +148,10 @@ int SimpleDHT11::sample(int pin, byte data[40]) {
     // DHT11 EOF:
     //    1. PULL LOW 50us.
     if (confirm(pin, 50, LOW)) {
-        return ErrDataEOF;
+        return SimpleDHTErrDataEOF;
     }
 
-    return ErrSuccess;
+    return SimpleDHTErrSuccess;
 }
 
 int SimpleDHT22::sample(int pin, byte data[40]) {
@@ -181,10 +173,10 @@ int SimpleDHT22::sample(int pin, byte data[40]) {
     //    1. PULL LOW 80us
     //    2. PULL HIGH 80us
     if (confirm(pin, 80, LOW)) {
-        return ErrStartLow;
+        return SimpleDHTErrStartLow;
     }
     if (confirm(pin, 80, HIGH)) {
-        return ErrStartHigh;
+        return SimpleDHTErrStartHigh;
     }
 
     // DHT11 data transmite:
@@ -193,7 +185,7 @@ int SimpleDHT22::sample(int pin, byte data[40]) {
     //    3. PULL HIGH 70us, bit(1)
     for (int j = 0; j < 40; j++) {
         if (confirm(pin, 50, LOW)) {
-            return ErrDataLow;
+            return SimpleDHTErrDataLow;
         }
 
         // read a bit, should never call method,
@@ -209,7 +201,7 @@ int SimpleDHT22::sample(int pin, byte data[40]) {
             delayMicroseconds(10);
         }
         if (!ok) {
-            return ErrDataRead;
+            return SimpleDHTErrDataRead;
         }
         data[j] = (tick > 3? 1:0);
     }
@@ -217,9 +209,9 @@ int SimpleDHT22::sample(int pin, byte data[40]) {
     // DHT11 EOF:
     //    1. PULL LOW 50us.
     if (confirm(pin, 50, LOW)) {
-        return ErrDataEOF;
+        return SimpleDHTErrDataEOF;
     }
 
-    return ErrSuccess;
+    return SimpleDHTErrSuccess;
 }
 
diff --git a/SimpleDHT.h b/SimpleDHT.h
index 63eec49..6b67f76 100644
--- a/SimpleDHT.h
+++ b/SimpleDHT.h
@@ -27,22 +27,22 @@
 
 #include <Arduino.h>
 
+// Success.
+#define SimpleDHTErrSuccess 0
+// Error to wait for start low signal.
+#define SimpleDHTErrStartLow 100
+// Error to wait for start high signal.
+#define SimpleDHTErrStartHigh 101
+// Error to wait for data start low signal.
+#define SimpleDHTErrDataLow 102
+// Error to wait for data read signal.
+#define SimpleDHTErrDataRead 103
+// Error to wait for data EOF signal.
+#define SimpleDHTErrDataEOF 104
+// Error to validate the checksum.
+#define SimpleDHTErrDataChecksum 105
+
 class SimpleDHT {
-public:
-    // Success.
-    static int ErrSuccess;
-    // Error to wait for start low signal.
-    static int ErrStartLow;
-    // Error to wait for start high signal.
-    static int ErrStartHigh;
-    // Error to wait for data start low signal.
-    static int ErrDataLow;
-    // Error to wait for data read signal.
-    static int ErrDataRead;
-    // Error to wait for data EOF signal.
-    static int ErrDataEOF;
-    // Error to validate the checksum.
-    static int ErrDataChecksum;
 public:
     // to read from dht11.
     // @param pin the DHT11 pin.
@@ -50,7 +50,7 @@ class SimpleDHT {
     // @param phumidity output, NULL to ignore.
     // @param pdata output 40bits sample, NULL to ignore.
     // @remark the min delay for this method is 1s.
-    // @return SimpleDHT11::ErrSuccess is success; otherwise, failed.
+    // @return SimpleDHTErrSuccess is success; otherwise, failed.
     int read(int pin, byte* ptemperature, byte* phumidity, byte pdata[40]);
 protected:
     // confirm the OUTPUT is level in us, 
@@ -76,7 +76,6 @@ class SimpleDHT {
     int parse(byte data[40], byte* ptemperature, byte* phumidity);
 };
 
-
 /*
     Simple DHT11
 
diff --git a/examples/DHT11Default/DHT11Default.ino b/examples/DHT11Default/DHT11Default.ino
index 7b44047..e7e5e7a 100644
--- a/examples/DHT11Default/DHT11Default.ino
+++ b/examples/DHT11Default/DHT11Default.ino
@@ -19,8 +19,8 @@ void loop() {
   // read without samples.
   byte temperature = 0;
   byte humidity = 0;
-  int err = SimpleDHT::ErrSuccess; 
-  if ((err = dht11.read(pinDHT11, &temperature, &humidity, NULL)) != SimpleDHT::ErrSuccess) {
+  int err = SimpleDHTErrSuccess;
+  if ((err = dht11.read(pinDHT11, &temperature, &humidity, NULL)) != SimpleDHTErrSuccess) {
     Serial.print("Read DHT11 failed, err="); Serial.print(err);
     return;
   }
diff --git a/examples/DHT11WithRawBits/DHT11WithRawBits.ino b/examples/DHT11WithRawBits/DHT11WithRawBits.ino
index 3110f13..9fa3c71 100644
--- a/examples/DHT11WithRawBits/DHT11WithRawBits.ino
+++ b/examples/DHT11WithRawBits/DHT11WithRawBits.ino
@@ -20,8 +20,8 @@ void loop() {
   byte temperature = 0;
   byte humidity = 0;
   byte data[40] = {0};
-  int err = SimpleDHT::ErrSuccess;
-  if ((err = dht11.read(pinDHT11, &temperature, &humidity, data)) != SimpleDHT::ErrSuccess) {
+  int err = SimpleDHTErrSuccess;
+  if ((err = dht11.read(pinDHT11, &temperature, &humidity, data)) != SimpleDHTErrSuccess) {
     Serial.print("Read DHT11 failed, err="); Serial.print(err);
     return;
   }
diff --git a/examples/DHT22Default/DHT22Default.ino b/examples/DHT22Default/DHT22Default.ino
index 3c240c4..f5fbd05 100644
--- a/examples/DHT22Default/DHT22Default.ino
+++ b/examples/DHT22Default/DHT22Default.ino
@@ -19,8 +19,8 @@ void loop() {
   // read without samples.
   byte temperature = 0;
   byte humidity = 0;
-  int err = SimpleDHT::ErrSuccess; 
-  if ((err = dht22.read(pinDHT22, &temperature, &humidity, NULL)) != SimpleDHT::ErrSuccess) {
+  int err = SimpleDHTErrSuccess;
+  if ((err = dht22.read(pinDHT22, &temperature, &humidity, NULL)) != SimpleDHTErrSuccess) {
     Serial.print("Read DHT22 failed, err="); Serial.print(err);
     return;
   }
diff --git a/examples/TwoSensorsDefault/TwoSensorsDefault.ino b/examples/TwoSensorsDefault/TwoSensorsDefault.ino
index d157104..ec7216c 100644
--- a/examples/TwoSensorsDefault/TwoSensorsDefault.ino
+++ b/examples/TwoSensorsDefault/TwoSensorsDefault.ino
@@ -25,8 +25,8 @@ void loop() {
   // read without samples.
   byte temperature = 0;
   byte humidity = 0;
-  int err = SimpleDHT::ErrSuccess;
-  if ((err = dht11.read(dataPinSensor1, &temperature, &humidity, NULL)) != SimpleDHT::ErrSuccess) {
+  int err = SimpleDHTErrSuccess;
+  if ((err = dht11.read(dataPinSensor1, &temperature, &humidity, NULL)) != SimpleDHTErrSuccess) {
     Serial.print("Communication error with Sensor 1, err="); Serial.print(err);
     return;
   }
@@ -47,7 +47,7 @@ void loop() {
 
   byte temperature2 = 0;
   byte humidity2 = 0;
-  if ((err = dht11.read(dataPinSensor2, &temperature, &humidity, NULL)) != SimpleDHT::ErrSuccess) {
+  if ((err = dht11.read(dataPinSensor2, &temperature, &humidity, NULL)) != SimpleDHTErrSuccess) {
     Serial.print("Communication error with Sensor 2, err="); Serial.print(err);
     return;
   }
diff --git a/library.properties b/library.properties
index 505e116..4c6bd74 100644
--- a/library.properties
+++ b/library.properties
@@ -1,5 +1,5 @@
 name=SimpleDHT
-version=1.0.2
+version=1.0.4
 author=Winlin <winlin@vip.126.com>
 maintainer=Winlin <winlin@vip.126.com>
 sentence=Arduino Temp & Humidity Sensors for DHT11 and DHT22.