Just another example of usefulness. This is a humidity and temperature sensor. Just powered by USB.
It consists of the following components:
- Seeeduino V2.21 (Atmega 328P)
- Grove – Temperature&Humidity Sensor Pro
- Grove – OLED 96×96
- Grove – Base Shield
It can be extended as follows. Connect a buzzer, alarm will sound when temperature or humidity falls outside a presettable threshold. Or better: connect it to the internet, for example to Pachube.
#include <Wire.h>
#include <SeedGrayOLED.h>
#include <avr/pgmspace.h<
#define DHT22_PIN 0 // ADC0
byte read_dht22_dat()
{
byte i = 0;
byte result=0;
for(i=0; i< 8; i++){
while(!(PINC & _BV(DHT22_PIN))); // wait for 50us
delayMicroseconds(30);
if(PINC & _BV(DHT22_PIN))
result |=(1<<(7-i));
while((PINC & _BV(DHT22_PIN))); // wait '1' finish
}
return result;
}
void setup()
{
DDRC |= _BV(DHT22_PIN);
PORTC |= _BV(DHT22_PIN);
Wire.begin();
SeeedGrayOled.init(); //initialize SEEED OLED display
SeeedGrayOled.clearDisplay(); //Clear Display.
SeeedGrayOled.setNormalDisplay(); //Set Normal Display Mode
SeeedGrayOled.setVerticalMode(); // Set to vertical mode for displaying text
SeeedGrayOled.setGrayLevel(12);
delay(2000); // Recommended delay before sensor can be used
}
void loop()
{
SeeedGrayOled.setTextXY(0,0);
SeeedGrayOled.setGrayLevel(12);
byte dht22_dat[5];
byte dht22_in;
byte i;
float humdity,temperature;
// start condition
// 1. pull-down i/o pin from 18ms
PORTC &= ~_BV(DHT22_PIN);
delay(18);
PORTC |= _BV(DHT22_PIN);
delayMicroseconds(40);
DDRC &= ~_BV(DHT22_PIN);
delayMicroseconds(40);
dht22_in = PINC & _BV(DHT22_PIN);
if(dht22_in){
Serial.println("sc 1 not met");
return;
}
delayMicroseconds(80);
dht22_in = PINC & _BV(DHT22_PIN);
if(!dht22_in){
SeeedGrayOled.putString("sc 2 not met");
return;
}
delayMicroseconds(80);
// now ready for data reception
for (i=0; i<5; i++)
dht22_dat[i] = read_dht22_dat();
DDRC |= _BV(DHT22_PIN);
PORTC |= _BV(DHT22_PIN);
byte dht22_check_sum = dht22_dat[0]+dht22_dat[1]+dht22_dat[2]+dht22_dat[3];
// check check_sum
if(dht22_dat[4]!= dht22_check_sum)
{
SeeedGrayOled.putString("checksum error");
}
humdity=((float)(dht22_dat[0]*256+dht22_dat[1]))/10;
temperature=((float)(dht22_dat[2]*256+dht22_dat[3]))/10;
SeeedGrayOled.putNumber(humdity);
SeeedGrayOled.putString("% ");
SeeedGrayOled.putNumber(temperature);
SeeedGrayOled.putString("C ");
delay(2000);
}