DHT22 - Plantilla para crear la libreria DHT para la plat…

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Plantilla para crear la libreria DHT para la plataforma FRDM

DHT22.cpp@1:5b20ff4fd227, 2011-07-04 (annotated)

Committer:: hwkit
Date:: Mon Jul 04 07:35:03 2011 +0000
Revision:: 1:5b20ff4fd227
Parent:: 0:547e68daeb1b
Child:: 2:340957cc8fef

Who changed what in which revision?

User	Revision	Line number	New contents of line
hwkit	0:547e68daeb1b	1	/*
hwkit	0:547e68daeb1b	2	DHT22.cpp - DHT22 sensor library
hwkit	0:547e68daeb1b	3	Developed by Ben Adams = 2011
hwkit	0:547e68daeb1b	4
hwkit	0:547e68daeb1b	5	This library is free software; you can redistribute it and / or
hwkit	0:547e68daeb1b	6	modify it under the terms of the GNU Leser General Public
hwkit	0:547e68daeb1b	7	License as published by the Free Software Foundation; either
hwkit	0:547e68daeb1b	8	version 2.1 of the License, or (at your option) any later version.
hwkit	0:547e68daeb1b	9
hwkit	0:547e68daeb1b	10	This library is distributed in the hope that it will be useful,
hwkit	0:547e68daeb1b	11	but WITHOUT ANY WARRENTY; without even the implied warranty of
hwkit	0:547e68daeb1b	12	MERCHANTABILITY or FITNESS FOR A PATRICULAR PURPOSE. See the GNU
hwkit	0:547e68daeb1b	13	Lesser General Public License for more details.
hwkit	0:547e68daeb1b	14
hwkit	0:547e68daeb1b	15	You should have received a copy of the GNU Lesser General Public
hwkit	0:547e68daeb1b	16	License along with this library; if not, write to the Free Software
hwkit	0:547e68daeb1b	17	Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
hwkit	0:547e68daeb1b	18
hwkit	0:547e68daeb1b	19
hwkit	0:547e68daeb1b	20	Humidity and Temperature Sensor DHT22 info found at
hwkit	0:547e68daeb1b	21	http://www.sparkfun.com/products/10167
hwkit	0:547e68daeb1b	22
hwkit	0:547e68daeb1b	23	Version 0.4: 24-Jan-2011 by Ben Adams
hwkit	0:547e68daeb1b	24	Added return code constants to keywords.txt
hwkit	0:547e68daeb1b	25	Return DHT_ERROR_CHECKSUM on check sum mismatch
hwkit	0:547e68daeb1b	26
hwkit	0:547e68daeb1b	27	Version 0.3: 17-Jan-2011 by Ben Adams
hwkit	0:547e68daeb1b	28	This version reads data
hwkit	0:547e68daeb1b	29	Needs check sum code added at the end of readData
hwkit	0:547e68daeb1b	30
hwkit	0:547e68daeb1b	31	Version 0.2: 16-Jan-2011 by Ben Adams
hwkit	0:547e68daeb1b	32	Changed coding style to match other Arduino Libraries.
hwkit	0:547e68daeb1b	33	This version will not read data either!
hwkit	0:547e68daeb1b	34
hwkit	0:547e68daeb1b	35	*/
hwkit	0:547e68daeb1b	36
hwkit	0:547e68daeb1b	37	#include "DHT22.h"
hwkit	0:547e68daeb1b	38
hwkit	1:5b20ff4fd227	39
hwkit	0:547e68daeb1b	40	// This should be 40, but the sensor is adding an extra bit at the start
hwkit	0:547e68daeb1b	41	#define DHT22_DATA_BIT_COUNT 41
hwkit	0:547e68daeb1b	42
hwkit	1:5b20ff4fd227	43	Serial pc(USBTX, USBRX); // Tx, Rx Using USB Virtual Serial Port
hwkit	1:5b20ff4fd227	44	// Read Data From /etc/ttyACM* (linux port)
hwkit	1:5b20ff4fd227	45
hwkit	0:547e68daeb1b	46	DHT22::DHT22(PinName Data) {
hwkit	0:547e68daeb1b	47	_data = Data; // Set Data Pin
hwkit	1:5b20ff4fd227	48	_lastReadTime = time(NULL);
hwkit	0:547e68daeb1b	49	_lastHumidity = 0;
hwkit	0:547e68daeb1b	50	_lastTemperature = DHT22_ERROR_VALUE;
hwkit	0:547e68daeb1b	51	}
hwkit	0:547e68daeb1b	52
hwkit	0:547e68daeb1b	53	DHT22::~DHT22() {
hwkit	0:547e68daeb1b	54	}
hwkit	0:547e68daeb1b	55
hwkit	0:547e68daeb1b	56	DHT22_ERROR DHT22::readData() {
hwkit	0:547e68daeb1b	57	int i, retryCount;
hwkit	1:5b20ff4fd227	58	int currentTemperature=0;
hwkit	1:5b20ff4fd227	59	int currentHumidity=0;
hwkit	1:5b20ff4fd227	60	unsigned int checkSum = 0, csPart1, csPart2, csPart3, csPart4;
hwkit	0:547e68daeb1b	61	unsigned int bitTimes[DHT22_DATA_BIT_COUNT];
hwkit	1:5b20ff4fd227	62	time_t currentTime = time(NULL);
hwkit	0:547e68daeb1b	63
hwkit	0:547e68daeb1b	64	DigitalInOut DATA(_data);
hwkit	0:547e68daeb1b	65
hwkit	1:5b20ff4fd227	66
hwkit	0:547e68daeb1b	67	for (i = 0; i < DHT22_DATA_BIT_COUNT; i++) {
hwkit	0:547e68daeb1b	68	bitTimes[i] = 0;
hwkit	0:547e68daeb1b	69	}
hwkit	1:5b20ff4fd227	70
hwkit	0:547e68daeb1b	71	if (currentTime - _lastReadTime < 2) {
hwkit	1:5b20ff4fd227	72	// Caller needs to wait 2 seconds between each call to read Data
hwkit	1:5b20ff4fd227	73	pc.printf("Current Time: %s\n",currentTime);
hwkit	1:5b20ff4fd227	74	pc.printf("Last Read Time: %s\n", _lastReadTime);
hwkit	0:547e68daeb1b	75	return DHT_ERROR_TOOQUICK;
hwkit	0:547e68daeb1b	76	}
hwkit	0:547e68daeb1b	77	_lastReadTime = currentTime;
hwkit	0:547e68daeb1b	78	retryCount = 0;
hwkit	0:547e68daeb1b	79	// Pin needs to start HIGH, wait unit it is HIGH with a timeout
hwkit	0:547e68daeb1b	80	do {
hwkit	0:547e68daeb1b	81	if (retryCount > 125) {
hwkit	0:547e68daeb1b	82	return DHT_BUS_HUNG;
hwkit	0:547e68daeb1b	83	}
hwkit	0:547e68daeb1b	84	retryCount ++;
hwkit	0:547e68daeb1b	85	wait_us(2);
hwkit	0:547e68daeb1b	86	} while (DATA==1);
hwkit	0:547e68daeb1b	87	// Send the activate pulse
hwkit	0:547e68daeb1b	88	DATA = 0; // MCU send out start signal to DHT22
hwkit	0:547e68daeb1b	89	wait_us(1100); // 1.1 ms
hwkit	0:547e68daeb1b	90	// Find the start of the ACK Pulse
hwkit	0:547e68daeb1b	91	retryCount = 0;
hwkit	0:547e68daeb1b	92	do {
hwkit	0:547e68daeb1b	93	if (retryCount > 25) {// (Spec is 20 to 40 us, 25*2 == 50us
hwkit	0:547e68daeb1b	94	return DHT_ERROR_NOT_PRESENT;
hwkit	0:547e68daeb1b	95	}
hwkit	0:547e68daeb1b	96	retryCount ++;
hwkit	0:547e68daeb1b	97	wait_us(2);
hwkit	0:547e68daeb1b	98	} while (DATA==1);
hwkit	0:547e68daeb1b	99	// Find the end of the ACK Pulse
hwkit	0:547e68daeb1b	100	retryCount = 0;
hwkit	0:547e68daeb1b	101	do {
hwkit	0:547e68daeb1b	102	if (retryCount > 50) {// (Spec is 80 us, 50 * 2 == 100us)
hwkit	0:547e68daeb1b	103	return DHT_ERROR_ACK_TOO_LONG;
hwkit	0:547e68daeb1b	104	}
hwkit	0:547e68daeb1b	105	retryCount++;
hwkit	0:547e68daeb1b	106	wait_us(2);
hwkit	0:547e68daeb1b	107	} while (DATA==0);
hwkit	0:547e68daeb1b	108	// Read the 40 bit data stream
hwkit	0:547e68daeb1b	109	for (i=0; i < DHT22_DATA_BIT_COUNT; i++) {
hwkit	0:547e68daeb1b	110	retryCount = 0;
hwkit	0:547e68daeb1b	111	do {
hwkit	0:547e68daeb1b	112	if (retryCount > 35) { // spec is 50 u, 35*2 = 70 us
hwkit	0:547e68daeb1b	113	return DHT_ERROR_SYNC_TIMEOUT;
hwkit	0:547e68daeb1b	114	}
hwkit	0:547e68daeb1b	115	retryCount ++;
hwkit	0:547e68daeb1b	116	wait_us(2);
hwkit	0:547e68daeb1b	117	} while (DATA==1);
hwkit	0:547e68daeb1b	118	// Measure the width of the data pulse
hwkit	0:547e68daeb1b	119	retryCount = 0;
hwkit	0:547e68daeb1b	120	do {
hwkit	0:547e68daeb1b	121	if (retryCount > 50) { // spec is 80us, 50*2 == 100us
hwkit	0:547e68daeb1b	122	return DHT_ERROR_DATA_TIMEOUT;
hwkit	0:547e68daeb1b	123	}
hwkit	0:547e68daeb1b	124	retryCount++;
hwkit	0:547e68daeb1b	125	wait_us(2);
hwkit	0:547e68daeb1b	126	} while (DATA==0);
hwkit	0:547e68daeb1b	127	bitTimes[i] = retryCount;
hwkit	0:547e68daeb1b	128	}
hwkit	0:547e68daeb1b	129
hwkit	0:547e68daeb1b	130	// Now bitTimes have the number of retries (us *2)
hwkit	0:547e68daeb1b	131	// that were needed to find the end of each data bit
hwkit	0:547e68daeb1b	132	// Spec: 0 is 26 to 28 us
hwkit	0:547e68daeb1b	133	// Spec: 1 is 70 us
hwkit	0:547e68daeb1b	134	// bitTimes[x] <= 11 is a 0
hwkit	0:547e68daeb1b	135	// bitTimes[x] > 11 is a 1
hwkit	0:547e68daeb1b	136	// Note: the bits are offset by one from the data sheet, not sure why
hwkit	0:547e68daeb1b	137	for (i=0; i<16; i++) {
hwkit	0:547e68daeb1b	138	if (bitTimes[i+1] > 11) {
hwkit	0:547e68daeb1b	139	currentHumidity \|= ( 1 << (15-i));
hwkit	0:547e68daeb1b	140	}
hwkit	0:547e68daeb1b	141	}
hwkit	0:547e68daeb1b	142
hwkit	0:547e68daeb1b	143	for (i=0; i<16; i ++) {
hwkit	0:547e68daeb1b	144	if (bitTimes[i+17] > 11) {
hwkit	0:547e68daeb1b	145	currentTemperature \|= (1 <<(15-i));
hwkit	0:547e68daeb1b	146	}
hwkit	0:547e68daeb1b	147	}
hwkit	0:547e68daeb1b	148
hwkit	0:547e68daeb1b	149	for (i=0; i<8; i++) {
hwkit	0:547e68daeb1b	150	if (bitTimes[i+33]>11) {
hwkit	0:547e68daeb1b	151	checkSum \|= (1 << (7-i));
hwkit	0:547e68daeb1b	152	}
hwkit	0:547e68daeb1b	153	}
hwkit	0:547e68daeb1b	154	_lastHumidity = (float(currentHumidity & 0x7FFF) / 10.0);
hwkit	0:547e68daeb1b	155	if (currentTemperature &= 0x8000) {
hwkit	0:547e68daeb1b	156	currentTemperature &= 0x7FFF;
hwkit	0:547e68daeb1b	157	_lastTemperature = (float(currentTemperature) / 10.0) * -1.0;
hwkit	0:547e68daeb1b	158	} else {
hwkit	0:547e68daeb1b	159	_lastTemperature = float(currentTemperature) / 10.0;
hwkit	0:547e68daeb1b	160	}
hwkit	0:547e68daeb1b	161
hwkit	0:547e68daeb1b	162	// Calculate Check Sum
hwkit	0:547e68daeb1b	163	csPart1 = currentHumidity >> 8;
hwkit	0:547e68daeb1b	164	csPart2 = currentHumidity & 0xFF;
hwkit	0:547e68daeb1b	165	csPart3 = currentTemperature >> 8;
hwkit	0:547e68daeb1b	166	csPart4 = currentTemperature & 0xFF;
hwkit	0:547e68daeb1b	167	if (checkSum == ((csPart1 + csPart2 + csPart3 + csPart4) & 0xFF)) {
hwkit	0:547e68daeb1b	168	return DHT_ERROR_NONE;
hwkit	0:547e68daeb1b	169	}
hwkit	0:547e68daeb1b	170	return DHT_ERROR_CHECKSUM;
hwkit	0:547e68daeb1b	171	}
hwkit	0:547e68daeb1b	172
hwkit	0:547e68daeb1b	173	float DHT22::getTemperatureC() {
hwkit	0:547e68daeb1b	174	return _lastTemperature;
hwkit	0:547e68daeb1b	175	}
hwkit	0:547e68daeb1b	176
hwkit	0:547e68daeb1b	177	float DHT22::getHumidity() {
hwkit	0:547e68daeb1b	178	return _lastHumidity;
hwkit	0:547e68daeb1b	179	}

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Type:	Library
Created:	13 Dec 2018
Imports:	32
Forks:	0
Commits:	4
Dependents:	0
Dependencies:	0
Followers:	1

DHT22.cpp@1:5b20ff4fd227, 2011-07-04 (annotated)

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