A library for the use of DHT11, a temperature and humidity sensor

Dependents:   HTTP_SERVER2 lightweight-weather-station

DHT11.h

Committer:
gjanusz
Date:
20 months ago
Revision:
12:c5a7faaeddd6
Parent:
10:f0d789f49df7

File content as of revision 12:c5a7faaeddd6:

/* Copyright (c) 2014 Shigenori Inoue, MIT License
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy of this software 
 * and associated documentation files (the "Software"), to deal in the Software without restriction, 
 * including without limitation the rights to use, copy, modify, merge, publish, distribute, 
 * sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is 
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in all copies or 
 * substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING 
 * BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND 
 * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, 
 * DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, 
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
 */
 
#ifndef __DHT11__
#define __DHT11__
#include "mbed.h"

/**  Example:
 * @code
 * #include "mbed.h"
 * #include "DHT11.h"
 *
 * DHT11 d(PTD1);
 *
 * main()
 * {
 *     int s;
 *     s = d.readData();
 *     if (s != DHT11::OK) {
 *         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
     * @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.
     */
    int readData(void);

    /** Reading the humidity from the data
     * @return Humidity in %,
     * regardless of the error from readData()
     */
    int readHumidity(void);

    /** Reading the temperature from the data
     * @return Temperature in Celcius,
     * regardless of the error from readData()
     */
    int readTemperature(void);

    enum ErrorDHT11 {
        OK = 0,
        READ_TOO_OFTEN = 1,
        BUS_BUSY = 2,
        NOT_PRESENT = 3,
        NOT_READY = 4,
        CHKSUM_ERR = 5,
        WATCHDOG_ERR = 6,
    };

private:
    DigitalInOut io;
    InterruptIn io_irq;
    Timer t;
    uint32_t t_pulse_us;
    const static int t_tol_start;    
    const static int t_tol_pulse;
    bool first_time;
    uint64_t data;
    uint32_t chksum;
    uint32_t cnt;
    uint32_t wdt;
    bool eod;
    void init(void);
    void pos_edge(void);
    void neg_edge(void);
};

#endif