Humidity and temperature sensor on mega

Forum 2005-2010 (read only) Hardware Interfacing
1

I got this code, and it works perfectly on a Arduino Duemilanove. I got the sensor attached to a Electronic Brick Chassis V1.1 shield, and when I move that shield to my Seeeduino Mega, I only get "dht11 start condition 1 not met".

I am not entirely sure what this code actually does, only that it works on my Duemilanove, and on the same pin on the mega wont work.

Anyone of your smart heads out there that can figure out what is going on, and maybe know what the pin difference is between the two?

#define DHT11_PIN 5      // ADC0

byte read_dht11_dat()
{
  byte i = 0;
  byte result=0;
  for(i=0; i< 8; i++)
  {
    while(!(PINC & _BV(DHT11_PIN)));  // wait for 50us
    delayMicroseconds(30);

    if(PINC & _BV(DHT11_PIN))
    {
      result |=(1<<(7-i));
    }

    while((PINC & _BV(DHT11_PIN)));  // wait '1' finish
  }
  return result;
}

void setup()
{
  DDRC |= _BV(DHT11_PIN);
  PORTC |= _BV(DHT11_PIN);

  Serial.begin(9600);

  Serial.println("Ready");
  Serial.print("$CLEAR\r\n");
}

void loop()
{
  byte dht11_dat[5];
  byte dht11_in;
  byte i;
  // start condition
  // 1. pull-down i/o pin from 18ms
  PORTC &= ~_BV(DHT11_PIN);
  delay(18);
  PORTC |= _BV(DHT11_PIN);
  delayMicroseconds(40);

  DDRC &= ~_BV(DHT11_PIN);
  delayMicroseconds(40);

  dht11_in = PINC & _BV(DHT11_PIN);

  if(dht11_in)
  {
    Serial.println("dht11 start condition 1 not met");
    return;
  }
  delayMicroseconds(80);

  dht11_in = PINC & _BV(DHT11_PIN);

  if(!dht11_in)
  {
    Serial.println("dht11 start condition 2 not met");
    return;
  }

  delayMicroseconds(80);

  // now ready for data reception
  for (i=0; i<5; i++)
  {
    dht11_dat[i] = read_dht11_dat();
  }

  DDRC |= _BV(DHT11_PIN);
  PORTC |= _BV(DHT11_PIN);

  byte dht11_check_sum = dht11_dat[0]+dht11_dat[1]+dht11_dat[2]+dht11_dat[3];

  // check check_sum
  if(dht11_dat[4]!= dht11_check_sum)
  {
    Serial.print("$CLEAR\r\n");
    Serial.print("$GO 1 2\r\n");
    Serial.print("$PRINT Checksum error\r\n");
    delay(1000);
  }
  else
  {
    if (millis() < 10000) //Waiting to skip the first fast jumping numbers
    {
      Serial.print("$GO 1 1\r\n");
      Serial.print("$PRINT Collecting...\r\n");
      Serial.print("$GO 2 1\r\n");
      Serial.print("$PRINT ");
      Serial.print(map(100,0,10000,0,millis()));
      Serial.print("%\r\n");
      delay(100);
    }
    else
    {
      Serial.print("$GO 1 1\r\n");
      Serial.print("$PRINT Humdity      ");
      Serial.print(dht11_dat[0], DEC);
      Serial.print("%\r\n");

      Serial.print("$GO 2 1\r\n");
      Serial.print("$PRINT Temperature  ");
      Serial.print(dht11_dat[2], DEC);              
      Serial.print("C\r\n");
    }
    
    delay(500);
  }
}

The sensor: http://www.seeedstudio.com/depot/electronic-brick-indoor-temp-humidity-sensor-p-683.html?cPath=48_52

2

Check your pin assignments, they may be different on the two boards.

3

Pin should be right, if I set it to a pin where the sensor isn't connected, or if I disconnect the sensor, I am getting "dht11 start condition 2 not met" instead of "dht11 start condition 1 not met"

4

Or, hell... I don't know any longer... From the schematics, it looks like it is pin 55, but same result with that.