DHT11 Humidity/Temp sensor and Basic Stamp

Help & Support Robot Parts
1

Good evening,

I’m having troubles reading the 40 bit string from the DHT11. Does anyone have BS2 code they can share?

Thanks in advance
Gary

2

Thanks Coleman I’ll give it a shot.

Gary

3

Hi Gary,

You will need to adapt the code which is used by the Arduino. Note that they connect it to an analog pin on the Arduino. To get an idea of each function used, you can visit the Arduino website for more information.

[code]#define DHT11_PIN 0 // 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”);
}

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* = 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.println(“DHT11 checksum error”);
}
Serial.print(“Current humdity = “);
Serial.print(dht11_dat[0], DEC);
Serial.print(”.”);
Serial.print(dht11_dat[1], DEC);
Serial.print("% ");
Serial.print(“temperature = “);
Serial.print(dht11_dat[2], DEC);
Serial.print(”.”);
Serial.print(dht11_dat[3], DEC);
Serial.println("C ");
delay(2000);
}
[/code]*