Plamen Totev
/
peltier
peltier with 2 fans
SEN11301P/DHT.cpp
- Committer:
- redplam
- Date:
- 2014-04-14
- Revision:
- 4:5213bee8158e
File content as of revision 4:5213bee8158e:
#include "DHT.h" #define DHT_DATA_BIT_COUNT 40 DHT::DHT(PinName pin,int DHTtype) { _pin = pin; _DHTtype = DHTtype; _firsttime=true; } DHT::~DHT() { } int DHT::readData() { int i, j, retryCount,b; unsigned int bitTimes[DHT_DATA_BIT_COUNT]; eError err = ERROR_NONE; time_t currentTime = time(NULL); DigitalInOut DHT_io(_pin); for (i = 0; i < DHT_DATA_BIT_COUNT; i++) { bitTimes[i] = 0; } if (!_firsttime) { if (int(currentTime - _lastReadTime) < 2) { err = ERROR_NO_PATIENCE; return err; } } else { _firsttime=false; _lastReadTime=currentTime; } retryCount = 0; do { if (retryCount > 125) { err = BUS_BUSY; return err; } retryCount ++; wait_us(2); } while ((DHT_io==0)); DHT_io.output(); DHT_io = 0; wait_ms(18); DHT_io = 1; wait_us(40); DHT_io.input(); retryCount = 0; do { if (retryCount > 40) { err = ERROR_NOT_PRESENT; return err; } retryCount++; wait_us(1); } while ((DHT_io==1)); if (err != ERROR_NONE) { return err; } wait_us(80); for (i = 0; i < 5; i++) { for (j = 0; j < 8; j++) { retryCount = 0; do { if (retryCount > 75) { err = ERROR_DATA_TIMEOUT; return err; } retryCount++; wait_us(1); } while (DHT_io == 0); wait_us(40); bitTimes[i*8+j]=DHT_io; int count = 0; while (DHT_io == 1 && count < 100) { wait_us(1); count++; } } } DHT_io.output(); DHT_io = 1; for (i = 0; i < 5; i++) { b=0; for (j=0; j<8; j++) { if (bitTimes[i*8+j+1] > 0) { b |= ( 1 << (7-j)); } } DHT_data[i]=b; } //if (DHT_data[4] == ((DHT_data[0] + DHT_data[1] + DHT_data[2] + DHT_data[3]) & 0xFF)) { _lastReadTime = currentTime; _lastTemperature=CalcTemperature(); _lastHumidity=CalcHumidity(); //} else { // err = ERROR_CHECKSUM; //} return err; } float DHT::CalcTemperature() { int v; switch (_DHTtype) { case DHT11: v = DHT_data[2]; return float(v); case DHT22: v = DHT_data[2] & 0x7F; v *= 256; v += DHT_data[3]; v /= 10; if (DHT_data[2] & 0x80) v *= -1; return float(v); } return 0; } float DHT::ReadHumidity() { return _lastHumidity; } float DHT::ConvertCelciustoFarenheit(float celsius) { return celsius * 9 / 5 + 32; } float DHT::ConvertCelciustoKelvin(float celsius) { return celsius + 273.15; } // dewPoint function NOAA // reference: http://wahiduddin.net/calc/density_algorithms.htm float DHT::CalcdewPoint(float celsius, float humidity) { float A0= 373.15/(273.15 + celsius); float SUM = -7.90298 * (A0-1); SUM += 5.02808 * log10(A0); SUM += -1.3816e-7 * (pow(10, (11.344*(1-1/A0)))-1) ; SUM += 8.1328e-3 * (pow(10,(-3.49149*(A0-1)))-1) ; SUM += log10(1013.246); float VP = pow(10, SUM-3) * humidity; float T = log(VP/0.61078); // temp var return (241.88 * T) / (17.558-T); } // delta max = 0.6544 wrt dewPoint() // 5x faster than dewPoint() // reference: http://en.wikipedia.org/wiki/Dew_point float DHT::CalcdewPointFast(float celsius, float humidity) { float a = 17.271; float b = 237.7; float temp = (a * celsius) / (b + celsius) + log(humidity/100); float Td = (b * temp) / (a - temp); return Td; } float DHT::ReadTemperature(eScale Scale) { if (Scale == FARENHEIT) return ConvertCelciustoFarenheit(_lastTemperature); else if (Scale == KELVIN) return ConvertCelciustoKelvin(_lastTemperature); else return _lastTemperature; } float DHT::CalcHumidity() { int v; switch (_DHTtype) { case DHT11: v = DHT_data[0]; return float(v); case DHT22: v = DHT_data[0]; v *= 256; v += DHT_data[1]; v /= 10; return float(v); } return 0; }