+ version 0.1.01 (first working DHT22 simulation)

+ improved protocol implementation + refactor to get code in logical place + support for negative temperature + improved comments

Author: RobTillaart

sketches/DHT_Simulator/DHT_Simulator.ino

@@ -1,7 +1,7 @@
 //
 // FILE: DHT_simulator.ino
 // AUTHOR: Rob Tillaart
-// VERSION: 0.1.00
+// VERSION: 0.1.01
 // PURPOSE: 
 // DATE: 2014-06-14
 // URL:
@@ -12,15 +12,15 @@
 // TODO
 // - robustness
 // - timeout loops
-// - get timing accurate
 
 const int dataPin = 5;
 byte b[5];
 
 void setup() 
 {
  Serial.begin(115200);
- Serial.println("Start ");
+ Serial.print("Start ");
+ Serial.println(__FILE__);
 
  pinMode(dataPin, INPUT_PULLUP);
 }
@@ -46,80 +46,80 @@ void loop()
  if (digitalRead(dataPin) == LOW) 
  {
  uint32_t start = micros();
- // wait until signal goes high // todo timeout onblocking loop?
- while (digitalRead(dataPin) == LOW);
+ // wait until signal goes high 
+ // todo timeout on blocking loop
+ while (digitalRead(dataPin) == LOW)
+ {
+ if (micros() - start > 1500) return; 
+ }
  if (micros() - start > 500) // serious request...
  {
-
- pinMode(dataPin, OUTPUT);
- // send ACK 
- digitalWrite(dataPin, LOW);
- delayMicroseconds(80); // overhead digitalwrite (2..4us)
- digitalWrite(dataPin, HIGH);
- delayMicroseconds(80);
-
  DHTsend(H, T);
 
- digitalWrite(dataPin, LOW);
- delayMicroseconds(50);
- pinMode(dataPin, INPUT_PULLUP);
-
- // for (int i = 0; i < 5; i++)
- // {
- // Serial.print(b[i]);
- // Serial.print(" ");
- // }
- // Serial.println();
-
  Serial.print(H);
  Serial.print("\t");
  Serial.println(T);
  }
  }
 }
 
+
 void DHTsend(int H, int T)
 {
- // prepare data
+ pinMode(dataPin, OUTPUT); 
+ // SEND ACK
+ digitalWrite(dataPin, LOW);
+ delayMicroseconds(80); // 80 us
+ digitalWrite(dataPin, HIGH);
+ delayMicroseconds(80); // 80 us
+
+ // PREPARE DATA
  b[0] = H / 256;
  b[1] = H & 255;
 
- uint16_t t;
- if (T >= 0) 
- {
- t = T;
- b[2] = 0;
- }
- else 
+ b[2] = 0;
+ if (T < 0) 
  {
- t = -T;
+ T = -T;
  b[2] = 0x80;
  }
- Serial.println(t);
 
- b[2] |= (t / 256);
- b[3] = (t & 255);
-
- b[4] = b[0] + b[1] + b[2] + b[3]; // CRC
+ b[2] |= T / 256;
+ b[3] = T & 255;
+ // CRC
+ b[4] = b[0] + b[1] + b[2] + b[3];
 
+ // SEND DATA
  for (int i = 0; i < 5; i++)
  {
  DHTsendbyte(b[i]);
  }
+
+ // END OF TRANSMISSION SIGNAL
+ digitalWrite(dataPin, LOW);
+ delayMicroseconds(50); // 50 us
+ pinMode(dataPin, INPUT_PULLUP);
+
+ // DEBUG 
+ // for (int i = 0; i < 5; i++)
+ // {
+ // Serial.print(b[i]);
+ // Serial.print(" ");
+ // }
+ // Serial.println();
 }
 
+// timing manual tuned
 void DHTsendbyte(byte b)
 {
  byte mask = 128;
  for(int i = 0; i < 8; i++)
  {
  digitalWrite(dataPin, LOW);
- delayMicroseconds(45); // overhead digitalwrite (2..4us)
+ delayMicroseconds(45); // 50 us
  digitalWrite(dataPin, HIGH);
-
- if (b & mask) delayMicroseconds(60); // idem
- else delayMicroseconds(24); // idem
-
+ if (b & mask) delayMicroseconds(60); // 70 us
+ else delayMicroseconds(24); // 26 us
  mask >>= 1;
  }
 }
@@ -139,3 +139,6 @@ void DHTsendbyte(byte b)
 
 
 
+
+
+