![](/media/cache/img/default_profile.jpg.50x50_q85.jpg)
Modified DHT11 Library with floated variable to allow readings in Centigrade
Fork of DHT11 by
Dht11.cpp
- Committer:
- fossum_13
- Date:
- 2015-02-15
- Revision:
- 0:c1da310d3e8a
- Child:
- 1:5da6f6de3e42
File content as of revision 0:c1da310d3e8a:
#include "Dht11.h" Dht11::Dht11(PinName p) : _pin(p) { // Set creation time so we can make // sure we pause at least 1 second for // startup. _timer.start(); } // Return values: // DHTLIB_OK // DHTLIB_ERROR_CHECKSUM // DHTLIB_ERROR_TIMEOUT int Dht11::read() { // 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; // Verify sensor settled after boot while(_timer.read_ms() < 1500) {} _timer.stop(); // Notify it we are ready to read _pin.output(); _pin = 0; wait_ms(18); _pin = 1; wait_us(40); _pin.input(); // ACKNOWLEDGE or TIMEOUT unsigned int loopCnt = 10000; while(_pin == 0) if (loopCnt-- == 0) return DHTLIB_ERROR_TIMEOUT; loopCnt = 10000; while(_pin == 1) 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(_pin == 0) if (loopCnt-- == 0) return DHTLIB_ERROR_TIMEOUT; //unsigned long t = micros(); Timer t; t. start(); loopCnt = 10000; while(_pin == 1) if (loopCnt-- == 0) return DHTLIB_ERROR_TIMEOUT; if (t.read_us() > 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; } int Dht11::temperature() { return(_temperature); } int Dht11::humidity() { return(_humidity); }