DHT library modify for DHT11 - DHT22 - AM2302
Fork of DHT by
Diff: DHT.cpp
- Revision:
- 2:df22ddf10d75
- Parent:
- 1:25c96950b6ed
- Child:
- 3:24682a533803
diff -r 25c96950b6ed -r df22ddf10d75 DHT.cpp --- a/DHT.cpp Wed Jul 24 06:59:28 2013 +0000 +++ b/DHT.cpp Fri Aug 15 20:55:43 2014 +0000 @@ -9,7 +9,7 @@ * * Copyright (C) Wim De Roeve * based on DHT22 sensor library by HO WING KIT - * Arduino DHT11 library + * Arduino DHT11 library * * Permission is hereby granted, free of charge, to any person obtaining a copy * of this software and associated documnetation files (the "Software"), to deal @@ -32,113 +32,99 @@ #include "DHT.h" -#define DHT_DATA_BIT_COUNT 41 +#define DHT_DATA_BIT_COUNT 40 -DHT::DHT(PinName pin,int DHTtype) { +DHT::DHT(PinName pin, eType DHTtype) +{ _pin = pin; _DHTtype = DHTtype; - _firsttime=true; + _firsttime = true; +} + +DHT::~DHT() +{ + } -DHT::~DHT() { +eError DHT::stall(DigitalInOut &io, int const level, int const max_time) +{ + int cnt = 0; + while (level == io) { + if (cnt > max_time) { + return ERROR_NO_PATIENCE; + } + cnt++; + wait_us(1); + } + return ERROR_NONE; } -int DHT::readData() { - int i, j, retryCount,b; - unsigned int bitTimes[DHT_DATA_BIT_COUNT]; +eError DHT::readData() +{ + uint8_t i = 0, j = 0, b = 0, data_valid = 0; + uint32_t bit_value[DHT_DATA_BIT_COUNT] = {0}; 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 0 - if (!_firsttime) { - if (int(currentTime - _lastReadTime) < 2) { - err = ERROR_NO_PATIENCE; - return err; - } - } else { - _firsttime=false; - _lastReadTime=currentTime; + // IO must be in hi state to start + if (ERROR_NONE != stall(DHT_io, 0, 250)) { + return BUS_BUSY; } -#endif - retryCount = 0; - do { - if (retryCount > 125) { - err = BUS_BUSY; - return err; - } - retryCount ++; - wait_us(2); - } while ((DHT_io==0)); - - + // start the transfer DHT_io.output(); DHT_io = 0; - wait_ms(18); + // only 500uS for DHT22 but 18ms for DHT11 + (_DHTtype == 11) ? wait_ms(18) : wait(1); DHT_io = 1; - wait_us(40); + wait_us(30); 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 till the sensor grabs the bus + if (ERROR_NONE != stall(DHT_io, 1, 40)) { + return ERROR_NOT_PRESENT; } - - wait_us(80); - + // sensor should signal low 80us and then hi 80us + if (ERROR_NONE != stall(DHT_io, 0, 100)) { + return ERROR_SYNC_TIMEOUT; + } + if (ERROR_NONE != stall(DHT_io, 1, 100)) { + return ERROR_NO_PATIENCE; + } + // capture the data 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); + if (ERROR_NONE != stall(DHT_io, 0, 75)) { + return ERROR_DATA_TIMEOUT; + } + // logic 0 is 28us max, 1 is 70us wait_us(40); - bitTimes[i*8+j]=DHT_io; - - int count = 0; - while (DHT_io == 1 && count < 100) { - wait_us(1); - count++; + bit_value[i*8+j] = DHT_io; + if (ERROR_NONE != stall(DHT_io, 1, 50)) { + return ERROR_DATA_TIMEOUT; } } } - DHT_io.output(); - DHT_io = 1; + // store the data 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)); + if (bit_value[i*8+j] == 1) { + 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)) { + // uncomment to see the checksum error if it exists + //printf(" 0x%02x + 0x%02x + 0x%02x + 0x%02x = 0x%02x \n", DHT_data[0], DHT_data[1], DHT_data[2], DHT_data[3], DHT_data[4]); + data_valid = DHT_data[0] + DHT_data[1] + DHT_data[2] + DHT_data[3]; + if (DHT_data[4] == data_valid) { _lastReadTime = currentTime; - _lastTemperature=CalcTemperature(); - _lastHumidity=CalcHumidity(); + _lastTemperature = CalcTemperature(); + _lastHumidity = CalcHumidity(); } else { err = ERROR_CHECKSUM; @@ -148,7 +134,8 @@ } -float DHT::CalcTemperature() { +float DHT::CalcTemperature() +{ int v; switch (_DHTtype) { @@ -167,21 +154,25 @@ return 0; } -float DHT::ReadHumidity() { +float DHT::ReadHumidity() +{ return _lastHumidity; } -float DHT::ConvertCelciustoFarenheit(float celsius) { +float DHT::ConvertCelciustoFarenheit(float const celsius) +{ return celsius * 9 / 5 + 32; } -float DHT::ConvertCelciustoKelvin(float celsius) { +float DHT::ConvertCelciustoKelvin(float const celsius) +{ return celsius + 273.15; } // dewPoint function NOAA // reference: http://wahiduddin.net/calc/density_algorithms.htm -float DHT::CalcdewPoint(float celsius, float humidity) { +float DHT::CalcdewPoint(float const celsius, float const humidity) +{ float A0= 373.15/(273.15 + celsius); float SUM = -7.90298 * (A0-1); SUM += 5.02808 * log10(A0); @@ -196,16 +187,17 @@ // 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 DHT::CalcdewPointFast(float const celsius, float const 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 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) { +float DHT::ReadTemperature(eScale Scale) +{ if (Scale == FARENHEIT) return ConvertCelciustoFarenheit(_lastTemperature); else if (Scale == KELVIN) @@ -214,7 +206,8 @@ return _lastTemperature; } -float DHT::CalcHumidity() { +float DHT::CalcHumidity() +{ int v; switch (_DHTtype) {