Fred Barnes / lib_dht22

DHT22 library, based on Simon Cooksey's. Improved with some error checking and more rigid timing (interrupts off).

Fork of lib_dht22 by Jodie Perry

dht22.h@3:40df3c72813f, 2016-11-03 (annotated)

Committer:
co657_frmb
Date:
Thu Nov 03 11:08:45 2016 +0000
Revision:
3:40df3c72813f
Parent:
1:10ec58346011
Child:
4:30a98da09c59
fixed up some things, still need a touch more tidying.

Who changed what in which revision?

UserRevisionLine numberNew contents of line
co657_sjc80 0:257ba13e416e 1 /*
co657_sjc80 0:257ba13e416e 2 * (C) The University of Kent and Simon Cooksey 2015.
co657_sjc80 0:257ba13e416e 3 */
co657_sjc80 0:257ba13e416e 4
co657_sjc80 0:257ba13e416e 5 #ifndef __DHT22_h_
co657_sjc80 0:257ba13e416e 6 #define __DHT22_h_
co657_sjc80 0:257ba13e416e 7
co657_sjc80 0:257ba13e416e 8 // We'll pick a point to decide if a signal is 1 or 0 from.
co657_frmb 3:40df3c72813f 9 #define DHT22_SIGNAL_HIGH_LOW_BOUNDARY 40 // uS
co657_frmb 3:40df3c72813f 10 #define DHT22_START_BIT_TIME 1000 // uS
co657_sjc80 0:257ba13e416e 11 #define DHT22_START_BIT_RESPONSE 80 // uS
co657_sjc80 0:257ba13e416e 12
co657_sjc80 0:257ba13e416e 13
co657_sjc80 0:257ba13e416e 14 typedef struct {
co657_sjc80 0:257ba13e416e 15 int temp;
co657_sjc80 0:257ba13e416e 16 int humidity;
co657_sjc80 0:257ba13e416e 17 uint8_t checksum;
co657_frmb 3:40df3c72813f 18 char dummy[3];
co657_sjc80 0:257ba13e416e 19 } DHT22_data_t;
co657_sjc80 0:257ba13e416e 20
co657_sjc80 0:257ba13e416e 21 class DHT22 {
co657_sjc80 0:257ba13e416e 22 public:
co657_frmb 3:40df3c72813f 23 DHT22 (PinName pin) : dht22_s (pin), debug (PTB19)
co657_frmb 3:40df3c72813f 24 {
co657_frmb 3:40df3c72813f 25 dht22_s.input ();
co657_frmb 3:40df3c72813f 26 isinput = 1;
co657_frmb 3:40df3c72813f 27 }
co657_frmb 3:40df3c72813f 28
co657_frmb 3:40df3c72813f 29 int read (DHT22_data_t *ptr);
co657_sjc80 0:257ba13e416e 30 private:
co657_sjc80 0:257ba13e416e 31 DigitalInOut dht22_s;
co657_frmb 3:40df3c72813f 32 int isinput;
co657_frmb 3:40df3c72813f 33 DigitalOut debug;
co657_sjc80 0:257ba13e416e 34
co657_frmb 3:40df3c72813f 35 void wait_2us (void);
co657_frmb 3:40df3c72813f 36 void setinput (void);
co657_frmb 3:40df3c72813f 37 void setoutput (void);
co657_frmb 3:40df3c72813f 38
co657_frmb 3:40df3c72813f 39 int wait_for_level (int lvl, const int max);
co657_frmb 3:40df3c72813f 40 void send_start (void);
co657_frmb 3:40df3c72813f 41 int wait_start (void);
co657_frmb 3:40df3c72813f 42 int read_byte (void);
co657_sjc80 0:257ba13e416e 43 };
co657_sjc80 0:257ba13e416e 44
co657_sjc80 0:257ba13e416e 45 #endif // __DHT22_h_