基于Arduino的DHT11库文件

// // FILE: dht11.cpp // VERSION: 0.4.1 // PURPOSE: DHT11 Temperature & Humidity Sensor library for Arduino // LICENSE: GPL v3 (http://www.gnu.org/licenses/gpl.html) // // DATASHEET: http://www.micro4you.com/files/sensor/DHT11.pdf // // HISTORY: // George Hadjikyriacou - Original version (??) // Mod by SimKard - Version 0.2 (24/11/2010) // Mod by Rob Tillaart - Version 0.3 (28/03/2011) // + added comments // + removed all non DHT11 specific code // + added references // Mod by Rob Tillaart - Version 0.4 (17/03/2012) // + added 1.0 support // Mod by Rob Tillaart - Version 0.4.1 (19/05/2012) // + added error codes // #include "dht11.h" // Return values: // DHTLIB_OK // DHTLIB_ERROR_CHECKSUM // DHTLIB_ERROR_TIMEOUT int dht11::read(int pin) { // BUFFER TO RECEIVE uint8_t bits[5]; uint8_t cnt = 7; uint8_t idx = 0; // EMPTY BUFFER for (int i=0; i< 5; i++) bits[i] = 0; // REQUEST SAMPLE pinMode(pin, OUTPUT); digitalWrite(pin, LOW); delay(18); digitalWrite(pin, HIGH); delayMicroseconds(40); pinMode(pin, INPUT); // ACKNOWLEDGE or TIMEOUT unsigned int loopCnt = 10000; while(digitalRead(pin) == LOW) if (loopCnt-- == 0) return DHTLIB_ERROR_TIMEOUT; loopCnt = 10000; while(digitalRead(pin) == HIGH) if (loopCnt-- == 0) return DHTLIB_ERROR_TIMEOUT; // READ OUTPUT - 40 BITS => 5 BYTES or TIMEOUT for (int i=0; i<40; i++) { loopCnt = 10000; while(digitalRead(pin) == LOW) if (loopCnt-- == 0) return DHTLIB_ERROR_TIMEOUT; unsigned long t = micros(); loopCnt = 10000; while(digitalRead(pin) == HIGH) if (loopCnt-- == 0) return DHTLIB_ERROR_TIMEOUT; if ((micros() - t) > 40) bits[idx] |= (1 << cnt); if (cnt == 0) // next byte? { cnt = 7; // restart at MSB idx++; // next byte! } else cnt--; } // WRITE TO RIGHT VARS // as bits[1] and bits[3] are allways zero they are omitted in formulas. humidity = bits[0]; temperature = bits[2]; uint8_t sum = bits[0] + bits[2]; if (bits[4] != sum) return DHTLIB_ERROR_CHECKSUM; return DHTLIB_OK; } // // END OF FILE //