+ initial version (not working yet)

Author: RobTillaart

sketches/DHT_Simulator/DHT_Simulator.ino

@@ -0,0 +1,141 @@
+//
+// FILE: DHT_simulator.ino
+// AUTHOR: Rob Tillaart
+// VERSION: 0.1.00
+// PURPOSE: 
+// DATE: 2014-06-14
+// URL:
+//
+// Released to the public domain
+//
+
+// TODO
+// - robustness
+// - timeout loops
+// - get timing accurate
+
+const int dataPin = 5;
+byte b[5];
+
+void setup() 
+{
+ Serial.begin(115200);
+ Serial.println("Start ");
+
+ pinMode(dataPin, INPUT_PULLUP);
+}
+
+void loop() 
+{
+ // T = -200 .. 1800
+ analogRead(A2);
+ int T = analogRead(A2) * 2 - 200; 
+
+ // H = 0 .. 1000
+ analogRead(A0);
+ int H = analogRead(A0);
+ if (H > 1000) 
+ {
+ H = 1000; 
+ }
+ // Serial.print(H);
+ // Serial.print("\t");
+ // Serial.println(T);
+
+ // WAKE UP SIGNAL DETECTED
+ if (digitalRead(dataPin) == LOW) 
+ {
+ uint32_t start = micros();
+ // wait until signal goes high // todo timeout onblocking loop?
+ while (digitalRead(dataPin) == LOW);
+ 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
+ b[0] = H / 256;
+ b[1] = H & 255;
+
+ uint16_t t;
+ if (T >= 0) 
+ {
+ t = T;
+ b[2] = 0;
+ }
+ else 
+ {
+ 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
+
+ for (int i = 0; i < 5; i++)
+ {
+ DHTsendbyte(b[i]);
+ }
+}
+
+void DHTsendbyte(byte b)
+{
+ byte mask = 128;
+ for(int i = 0; i < 8; i++)
+ {
+ digitalWrite(dataPin, LOW);
+ delayMicroseconds(45); // overhead digitalwrite (2..4us)
+ digitalWrite(dataPin, HIGH);
+
+ if (b & mask) delayMicroseconds(60); // idem
+ else delayMicroseconds(24); // idem
+
+ mask >>= 1;
+ }
+}
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+