Fix #11, refine protocol, stat success rate

README.md

@@ -42,17 +42,18 @@ This library including the following examples:
 
 1. [DHT11Default](https://github.com/winlinvip/SimpleDHT/tree/master/examples/DHT11Default): Use DHT11 to sample.
 1. [DHT11WithRawBits](https://github.com/winlinvip/SimpleDHT/tree/master/examples/DHT11WithRawBits): Use DHT11 to sample and get the 40bits RAW data.
-1. [TwoSensorsDefault](https://github.com/winlinvip/SimpleDHT/tree/master/examples/TwoSensorsDefault): Use two DHT11 to sample.
+1. [DHT11ErrCount](https://github.com/winlinvip/SimpleDHT/tree/master/examples/DHT11ErrCount): Use DHT11 to sample and stat the success rate.
 1. [DHT22Default](https://github.com/winlinvip/SimpleDHT/tree/master/examples/DHT22Default): Use DHT22 to sample.
 1. [DHT22WithRawBits](https://github.com/winlinvip/SimpleDHT/tree/master/examples/DHT22WithRawBits): Use DHT22 to sample and get the 40bits RAW data.
 1. [DHT22Integer](https://github.com/winlinvip/SimpleDHT/tree/master/examples/DHT22Integer): Use DHT22 to sample and ignore the fractional data.
-
+1. [DHT22ErrCount](https://github.com/winlinvip/SimpleDHT/tree/master/examples/DHT22ErrCount): Use DHT22 to sample and stat the success rate.
+1. [TwoSensorsDefault](https://github.com/winlinvip/SimpleDHT/tree/master/examples/TwoSensorsDefault): Use two DHT11 to sample.
 
 ## Links
 
 1. [adafruit/DHT-sensor-library](https://github.com/adafruit/DHT-sensor-library)
 1. [Arduino #4469: Add SimpleDHT library.](https://github.com/arduino/Arduino/issues/4469)
-1. [DHT11 datasheet and protocol.](https://cdn-shop.adafruit.com/datasheets/DHT11-chinese.pdf)
-1. [DHT22 datasheet and protoocl.](https://cdn-shop.adafruit.com/datasheets/DHT22.pdf)
+1. [DHT11 datasheet and protocol.](https://akizukidenshi.com/download/ds/aosong/DHT11.pdf)
+1. [DHT22 datasheet and protoocl.](http://akizukidenshi.com/download/ds/aosong/AM2302.pdf)
 
 Winlin 2016.1

SimpleDHT.cpp

@@ -29,7 +29,7 @@ int SimpleDHT::read(int pin, byte* ptemperature, byte* phumidity, byte pdata[40]
 
     float temperature = 0;
     float humidity = 0;
-    if ((read2(pin, &temperature, &humidity, pdata)) != SimpleDHTErrSuccess) {
+    if ((ret = read2(pin, &temperature, &humidity, pdata)) != SimpleDHTErrSuccess) {
         return ret;
     }
 
@@ -45,16 +45,19 @@ int SimpleDHT::read(int pin, byte* ptemperature, byte* phumidity, byte pdata[40]
 }
 
 int SimpleDHT::confirm(int pin, int us, byte level) {
-    // wait one more count to ensure.
-    int cnt = us / 10 + 1;
+    int cnt = us / 10;
+    if ((us % 10) > 0) {
+        cnt++;
+    }
 
     bool ok = false;
     for (int i = 0; i < cnt; i++) {
+        delayMicroseconds(10);
+
         if (digitalRead(pin) != level) {
             ok = true;
             break;
         }
-        delayMicroseconds(10);
     }
 
     if (!ok) {
@@ -112,6 +115,11 @@ int SimpleDHT11::read2(int pin, float* ptemperature, float* phumidity, byte pdat
         *phumidity = (int)(humidity>>8);
     }
 
+    // For example, when remove the data line, it will be success with zero data.
+    if (temperature == 0 && humidity == 0) {
+        return SimpleDHTErrZeroSamples;
+    }
+
     return ret;
 }
 
@@ -130,7 +138,6 @@ int SimpleDHT11::sample(int pin, byte data[40]) {
     digitalWrite(pin, HIGH);
     pinMode(pin, INPUT);
     delayMicroseconds(30);
-
     // DHT11 starting:
     //    1. PULL LOW 80us
     //    2. PULL HIGH 80us
@@ -211,31 +218,31 @@ int SimpleDHT22::sample(int pin, byte data[40]) {
     // According to protocol: http://akizukidenshi.com/download/ds/aosong/AM2302.pdf
     // notify DHT11 to start: 
     //    1. T(be), PULL LOW 1ms(0.8-20ms).
-    //    2. T(go), PULL HIGH 30us(20-200us).
+    //    2. T(go), PULL HIGH 30us(20-200us), use 40us.
     //    3. SET TO INPUT.
     pinMode(pin, OUTPUT);
     digitalWrite(pin, LOW);
     delayMicroseconds(1000);
     digitalWrite(pin, HIGH);
     pinMode(pin, INPUT);
-    delayMicroseconds(30);
+    delayMicroseconds(40);
 
     // DHT11 starting:
-    //    1. T(rel), PULL LOW 80us(75-85us)
-    //    2. T(reh), PULL HIGH 80us(75-85us)
-    if (confirm(pin, 80, LOW)) {
+    //    1. T(rel), PULL LOW 80us(75-85us), use 90us.
+    //    2. T(reh), PULL HIGH 80us(75-85us), use 90us.
+    if (confirm(pin, 90, LOW)) {
         return SimpleDHTErrStartLow;
     }
-    if (confirm(pin, 80, HIGH)) {
+    if (confirm(pin, 90, HIGH)) {
         return SimpleDHTErrStartHigh;
     }
 
     // DHT11 data transmite:
-    //    1. T(LOW), 1bit start, PULL LOW 50us(48-55us)
+    //    1. T(LOW), 1bit start, PULL LOW 50us(48-55us), use 60us.
     //    2. T(H0), PULL HIGH 26us(22-30us), bit(0)
     //    3. T(H1), PULL HIGH 70us(68-75us), bit(1)
     for (int j = 0; j < 40; j++) {
-        if (confirm(pin, 50, LOW)) {
+        if (confirm(pin, 60, LOW)) {
             return SimpleDHTErrDataLow;
         }
 
@@ -258,8 +265,8 @@ int SimpleDHT22::sample(int pin, byte data[40]) {
     }
 
     // DHT11 EOF:
-    //    1. T(en), PULL LOW 50us(45-55us).
-    if (confirm(pin, 50, LOW)) {
+    //    1. T(en), PULL LOW 50us(45-55us), use 60us.
+    if (confirm(pin, 60, LOW)) {
         return SimpleDHTErrDataEOF;
     }
 

SimpleDHT.h

@@ -41,6 +41,8 @@
 #define SimpleDHTErrDataEOF 104
 // Error to validate the checksum.
 #define SimpleDHTErrDataChecksum 105
+// Error when temperature and humidity are zero, it shouldn't happen.
+#define SimpleDHTErrZeroSamples 106
 
 class SimpleDHT {
 public:
@@ -51,7 +53,7 @@ class SimpleDHT {
     //      For DHT11, in H, such as 35H.
     //      For DHT22, in RH%, such as 53%RH.
     // @param pdata output 40bits sample, NULL to ignore.
-    // @remark the min delay for this method is 1s.
+    // @remark the min delay for this method is 1s(DHT11) or 2s(DHT22).
     // @return SimpleDHTErrSuccess is success; otherwise, failed.
     virtual int read(int pin, byte* ptemperature, byte* phumidity, byte pdata[40]);
     // to get a more accurate data.

examples/DHT11Default/DHT11Default.ino

@@ -21,7 +21,7 @@ void loop() {
   byte humidity = 0;
   int err = SimpleDHTErrSuccess;
   if ((err = dht11.read(pinDHT11, &temperature, &humidity, NULL)) != SimpleDHTErrSuccess) {
-    Serial.print("Read DHT11 failed, err="); Serial.print(err);
+    Serial.print("Read DHT11 failed, err="); Serial.println(err);delay(1000);
     return;
   }
 
@@ -30,5 +30,5 @@ void loop() {
   Serial.print((int)humidity); Serial.println(" H");
 
   // DHT11 sampling rate is 1HZ.
-  delay(1000);
+  delay(1500);
 }

examples/DHT11ErrCount/DHT11ErrCount.ino

@@ -0,0 +1,40 @@
+#include <SimpleDHT.h>
+
+// for DHT11, 
+//      VCC: 5V or 3V
+//      GND: GND
+//      DATA: 2
+int pinDHT11 = 2;
+SimpleDHT11 dht11;
+
+void setup() {
+  Serial.begin(115200);
+}
+
+void loop() {
+  // start working...
+  Serial.println("=================================");
+  Serial.println("Sample DHT11 with error count");
+
+  int cnt = 0;
+  int err_cnt = 0;
+  for (;;) {
+    cnt++;
+
+    byte temperature = 0;
+    byte humidity = 0;
+    int err = SimpleDHTErrSuccess;
+    if ((err = dht11.read(pinDHT11, &temperature, &humidity, NULL)) != SimpleDHTErrSuccess) {
+      Serial.print("Read DHT11 failed, err="); Serial.println(err);err_cnt++;
+    }
+
+    Serial.print("DHT11, ");
+    Serial.print((int)temperature); Serial.print(" *C, ");
+    Serial.print((int)humidity); Serial.print(" H");
+    Serial.print(", total: "); Serial.print(cnt);
+    Serial.print(", err: "); Serial.print(err_cnt);
+    Serial.print(", success rate: "); Serial.print((cnt - err_cnt) * 100.0 / (float)cnt); Serial.println("%");
+
+    delay(1500);
+  }
+}

examples/DHT11WithRawBits/DHT11WithRawBits.ino

@@ -22,7 +22,7 @@ void loop() {
   byte data[40] = {0};
   int err = SimpleDHTErrSuccess;
   if ((err = dht11.read(pinDHT11, &temperature, &humidity, data)) != SimpleDHTErrSuccess) {
-    Serial.print("Read DHT11 failed, err="); Serial.print(err);
+    Serial.print("Read DHT11 failed, err="); Serial.println(err);delay(1000);
     return;
   }
 
@@ -40,5 +40,5 @@ void loop() {
   Serial.print((int)humidity); Serial.println(" H");
 
   // DHT11 sampling rate is 1HZ.
-  delay(1000);
+  delay(1500);
 }

examples/DHT22Default/DHT22Default.ino

@@ -23,7 +23,7 @@ void loop() {
   float humidity = 0;
   int err = SimpleDHTErrSuccess;
   if ((err = dht22.read2(pinDHT22, &temperature, &humidity, NULL)) != SimpleDHTErrSuccess) {
-    Serial.print("Read DHT22 failed, err="); Serial.print(err);
+    Serial.print("Read DHT22 failed, err="); Serial.println(err);delay(2000);
     return;
   }
 
@@ -32,5 +32,5 @@ void loop() {
   Serial.print((float)humidity); Serial.println(" RH%");
 
   // DHT22 sampling rate is 0.5HZ.
-  delay(2000);
+  delay(2500);
 }

examples/DHT22ErrCount/DHT22ErrCount.ino

@@ -0,0 +1,39 @@
+#include <SimpleDHT.h>
+
+// for DHT22, 
+//      VCC: 5V or 3V
+//      GND: GND
+//      DATA: 2
+int pinDHT22 = 2;
+SimpleDHT22 dht22;
+
+void setup() {
+  Serial.begin(115200);
+}
+
+void loop() {
+  // start working...
+  Serial.println("=================================");
+  Serial.println("Sample DHT22 with error count");
+
+  int cnt = 0;
+  int err_cnt = 0;
+  for (;;) {
+    cnt++;
+
+    float temperature = 0;
+    float humidity = 0;
+    int err = SimpleDHTErrSuccess;
+    if ((err = dht22.read2(pinDHT22, &temperature, &humidity, NULL)) != SimpleDHTErrSuccess) {
+      Serial.print("Read DHT22 failed, err="); Serial.println(err);err_cnt++;
+    }
+
+    Serial.print((float)temperature); Serial.print(" *C, ");
+    Serial.print((float)humidity); Serial.print(" RH%");
+    Serial.print(", total: "); Serial.print(cnt);
+    Serial.print(", err: "); Serial.print(err_cnt);
+    Serial.print(", success rate: "); Serial.print((cnt - err_cnt) * 100.0 / (float)cnt); Serial.println("%");
+
+    delay(2500);
+  }
+}

examples/DHT22Integer/DHT22Integer.ino

@@ -21,7 +21,7 @@ void loop() {
   byte humidity = 0;
   int err = SimpleDHTErrSuccess;
   if ((err = dht22.read(pinDHT22, &temperature, &humidity, NULL)) != SimpleDHTErrSuccess) {
-    Serial.print("Read DHT22 failed, err="); Serial.print(err);
+    Serial.print("Read DHT22 failed, err="); Serial.println(err);delay(2000);
     return;
   }
 
@@ -30,5 +30,5 @@ void loop() {
   Serial.print((int)humidity); Serial.println(" RH%");
 
   // DHT22 sampling rate is 0.5HZ.
-  delay(2000);
+  delay(2500);
 }

examples/DHT22WithRawBits/DHT22WithRawBits.ino

@@ -24,7 +24,7 @@ void loop() {
   byte data[40] = {0};
   int err = SimpleDHTErrSuccess;
   if ((err = dht22.read2(pinDHT22, &temperature, &humidity, data)) != SimpleDHTErrSuccess) {
-    Serial.print("Read DHT22 failed, err="); Serial.print(err);
+    Serial.print("Read DHT22 failed, err="); Serial.println(err);delay(2000);
     return;
   }
 
@@ -42,5 +42,5 @@ void loop() {
   Serial.print((float)humidity); Serial.println(" RH%");
 
   // DHT22 sampling rate is 0.5HZ.
-  delay(2000);
+  delay(2500);
 }

examples/TwoSensorsDefault/TwoSensorsDefault.ino

@@ -27,7 +27,7 @@ void loop() {
   byte humidity = 0;
   int err = SimpleDHTErrSuccess;
   if ((err = dht11.read(dataPinSensor1, &temperature, &humidity, NULL)) != SimpleDHTErrSuccess) {
-    Serial.print("Communication error with Sensor 1, err="); Serial.print(err);
+    Serial.print("Communication error with Sensor 1, err="); Serial.println(err);delay(1000);
     return;
   }
 
@@ -48,7 +48,7 @@ void loop() {
   byte temperature2 = 0;
   byte humidity2 = 0;
   if ((err = dht11.read(dataPinSensor2, &temperature, &humidity, NULL)) != SimpleDHTErrSuccess) {
-    Serial.print("Communication error with Sensor 2, err="); Serial.print(err);
+    Serial.print("Communication error with Sensor 2, err="); Serial.println(err);delay(1000);
     return;
   }