Jodie Perry / lib_dht22

A simple library for reading data from a DHT22 sensor

Fork of lib_dht22 by Simon Cooksey

dht22.h

Committer:
co657_sjc80
Date:
2016-01-04
Revision:
0:257ba13e416e
Child:
1:10ec58346011

File content as of revision 0:257ba13e416e:

/*
 * (C) The University of Kent and Simon Cooksey 2015.
 */

#ifndef __DHT22_h_
#define __DHT22_h_

// We'll pick a point to decide if a signal is 1 or 0 from. 
#define DHT22_SIGNAL_HIGH_LOW_BOUNDARY      50   // uS
#define DHT22_START_BIT_TIME                500  // uS
#define DHT22_START_BIT_RESPONSE            80   // uS

typedef enum {
    EDGE_TYPE_FALLING,
    EDGE_TYPE_RISING,
} edge_type_t;

typedef struct {
    int temp;
    int humidity;
    uint8_t checksum;
} DHT22_data_t;

class DHT22 {
public:
    DHT22(PinName pin)  : dht22_s(pin) { }
    void read(DHT22_data_t * data);
private:
    DigitalInOut dht22_s;
    Timer dht22_t;

    int wait_for_edge(edge_type_t type);
    void send_start();
    void await_start_response();
    int16_t read_word();
    uint8_t read_checksum();
};

#endif // __DHT22_h_