Simple library for the DHT11 temperature and humidity sensor. Forked from an existing Mbed DHT11 project.
Simple DHT11 temperature and humidity library.
Example usage
#include "mbed.h" #include "DHT11.h" DHT11 dht(D8); // Change pin name here if required main() { printf("T:%d, H:%d\r\n", dht.readTemperature(), dht.readHumidity()); }
The sensor may be read as often as desired, but temperature and humidity values are cached and will only be updated if they are more than 2 seconds old. This is the underlying sensor update rate.
Please note that this project has been modified only enough to make it work for its intended purpose. Various parts of this project still need work, and the source code should not be seen as an example of best practice.
Diff: DHT11.h
- Revision:
- 0:4d4c5ea17d86
- Child:
- 1:95b80cc3f676
diff -r 000000000000 -r 4d4c5ea17d86 DHT11.h --- /dev/null Thu Jan 01 00:00:00 1970 +0000 +++ b/DHT11.h Wed Sep 10 15:14:31 2014 +0000 @@ -0,0 +1,91 @@ +/** @file + Library for the use of the DHT11, a temperature and humidity sensor + Shigenori Inoue, September 10, 2014 + */ +#ifndef __DHT11__ +#define __DHT11__ +#include "mbed.h" + +/** Example: + * @code + * #include "mbed.h" + * #include "DHT11.h" + * + * DHT11 d; + * + * main() + * { + * int s; + * s = d.readData(); + * if (s != 0) { + * printf("Error!\r\n"); + * } + * else { + * printf("T:%d, H:%d\r\n", d.readTemperature(), d.readHumidity()); + * } + * } + * @endcode + */ + +class DHT11 +{ +public: + /** Create a DHT11 interface + * @param pin 1-wire-like serial I/O port of DHT11 + */ + DHT11(PinName pin); + ~DHT11(); + + /** Reading the data from the DHT11 */ + int readData(void); + + /** Reading the data from the DHT11 + * @return Error code + * 0: OK. + * 1: Reading the data too often. + * 2: 1-wire bus is busy. + * 3: DHT11 does not respond. + * 4: DHT11 is not ready. + * 5: Checksum is incorrect. + * 6: Timeout + */ + + /** Reading the humidity from the data + * @return Humidity in % if readData() returns no error. Otherwise, returns 0xffffffff. + */ + int readHumidity(void); + + /** Reading the humidity from the data + * @return Temperature in Celcius if readData() returns no error. Otherwise, returns 0xffffffff. + */ + int readTemperature(void); + + enum ErrorDHT11 { + OK = 0, + TOO_FAST_READ = 1, + BUS_BUSY = 2, + NOT_PRESENT = 3, + NOT_READY = 4, + CHKSUM_ERR = 5, + WATCHDOG_ERR = 6, + }; + +private: + PinName _pin; + DigitalInOut io; + InterruptIn io_irq; + Timer t; + uint32_t t_pulse_us; + bool first_time; + uint64_t data; + uint32_t chksum; + uint32_t cnt; + uint32_t wdt; + bool eod; + ErrorDHT11 err; + void init(void); + void pos_edge(void); + void neg_edge(void); +}; + +#endif \ No newline at end of file