wiringPi_Blueberry/wiringPi/rht03.c
2023-08-11 15:53:17 +08:00

257 lines
5.8 KiB
C

/*
* rht03.c:
* Extend wiringPi with the rht03 Maxdetect 1-Wire sensor.
* Copyright (c) 2016-2017 Gordon Henderson
***********************************************************************
* This file is part of wiringPi:
* https://projects.drogon.net/raspberry-pi/wiringpi/
*
* wiringPi is free software: you can redistribute it and/or modify
* it under the terms of the GNU Lesser General Public License as
* published by the Free Software Foundation, either version 3 of the
* License, or (at your option) any later version.
*
* wiringPi is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with wiringPi.
* If not, see <http://www.gnu.org/licenses/>.
***********************************************************************
*/
#include <sys/time.h>
#include <stdio.h>
#include <stdio.h>
#include <time.h>
#include "wiringPi.h"
#include "rht03.h"
#ifdef CONFIG_ORANGEPI
#include "OrangePi.h"
#endif
/*
* maxDetectLowHighWait:
* Wait for a transition from low to high on the bus
*********************************************************************************
*/
static int maxDetectLowHighWait (const int pin)
{
struct timeval now, timeOut, timeUp ;
// If already high then wait for pin to go low
gettimeofday (&now, NULL) ;
timerclear (&timeOut) ;
timeOut.tv_usec = 1000 ;
timeradd (&now, &timeOut, &timeUp) ;
while (digitalRead (pin) == HIGH)
{
gettimeofday (&now, NULL) ;
if (timercmp (&now, &timeUp, >))
return FALSE ;
}
// Wait for it to go HIGH
gettimeofday (&now, NULL) ;
timerclear (&timeOut) ;
timeOut.tv_usec = 1000 ;
timeradd (&now, &timeOut, &timeUp) ;
while (digitalRead (pin) == LOW)
{
gettimeofday (&now, NULL) ;
if (timercmp (&now, &timeUp, >))
return FALSE ;
}
return TRUE ;
}
/*
* maxDetectClockByte:
* Read in a single byte from the MaxDetect bus
*********************************************************************************
*/
static unsigned int maxDetectClockByte (const int pin)
{
unsigned int byte = 0 ;
int bit ;
for (bit = 0 ; bit < 8 ; ++bit)
{
if (!maxDetectLowHighWait (pin))
return 0 ;
// bit starting now - we need to time it.
delayMicroseconds (30) ;
byte <<= 1 ;
if (digitalRead (pin) == HIGH) // It's a 1
byte |= 1 ;
}
return byte ;
}
/*
* maxDetectRead:
* Read in and return the 4 data bytes from the MaxDetect sensor.
* Return TRUE/FALSE depending on the checksum validity
*********************************************************************************
*/
static int maxDetectRead (const int pin, unsigned char buffer [4])
{
int i ;
unsigned int checksum ;
unsigned char localBuf [5] ;
struct timeval now, then, took ;
// See how long we took
gettimeofday (&then, NULL) ;
// Wake up the RHT03 by pulling the data line low, then high
// Low for 10mS, high for 40uS.
pinMode (pin, OUTPUT) ;
digitalWrite (pin, 0) ; delay (10) ;
digitalWrite (pin, 1) ; delayMicroseconds (40) ;
pinMode (pin, INPUT) ;
// Now wait for sensor to pull pin low
if (!maxDetectLowHighWait (pin))
return FALSE ;
// and read in 5 bytes (40 bits)
for (i = 0 ; i < 5 ; ++i)
localBuf [i] = maxDetectClockByte (pin) ;
checksum = 0 ;
for (i = 0 ; i < 4 ; ++i)
{
buffer [i] = localBuf [i] ;
checksum += localBuf [i] ;
}
checksum &= 0xFF ;
// See how long we took
gettimeofday (&now, NULL) ;
timersub (&now, &then, &took) ;
// Total time to do this should be:
// 10mS + 40µS - reset
// + 80µS + 80µS - sensor doing its low -> high thing
// + 40 * (50µS + 27µS (0) or 70µS (1) )
// = 15010µS
// so if we take more than that, we've had a scheduling interruption and the
// reading is probably bogus.
if ((took.tv_sec != 0) || (took.tv_usec > 16000))
return FALSE ;
return checksum == localBuf [4] ;
}
/*
* myReadRHT03:
* Read the Temperature & Humidity from an RHT03 sensor
* Values returned are *10, so 123 is 12.3.
*********************************************************************************
*/
static int myReadRHT03 (const int pin, int *temp, int *rh)
{
int result ;
unsigned char buffer [4] ;
// Read ...
result = maxDetectRead (pin, buffer) ;
if (!result)
return FALSE ;
*rh = (buffer [0] * 256 + buffer [1]) ;
*temp = (buffer [2] * 256 + buffer [3]) ;
if ((*temp & 0x8000) != 0) // Negative
{
*temp &= 0x7FFF ;
*temp = -*temp ;
}
// Discard obviously bogus readings - the checksum can't detect a 2-bit error
// (which does seem to happen - no realtime here)
if ((*rh > 999) || (*temp > 800) || (*temp < -400))
return FALSE ;
return TRUE ;
}
/*
* myAnalogRead:
*********************************************************************************
*/
static int myAnalogRead (struct wiringPiNodeStruct *node, int pin)
{
int piPin = node->fd ;
int chan = pin - node->pinBase ;
int temp = -9997 ;
int rh = -9997 ;
int try ;
if (chan > 1)
return -9999 ; // Bad parameters
for (try = 0 ; try < 10 ; ++try)
{
if (myReadRHT03 (piPin, &temp, &rh))
return chan == 0 ? temp : rh ;
}
return -9998 ;
}
/*
* rht03Setup:
* Create a new instance of an RHT03 temperature sensor.
*********************************************************************************
*/
int rht03Setup (const int pinBase, const int piPin)
{
struct wiringPiNodeStruct *node ;
if ((piPin & PI_GPIO_MASK) != 0) // Must be an on-board pin
return FALSE ;
// 2 pins - temperature and humidity
node = wiringPiNewNode (pinBase, 2) ;
node->fd = piPin ;
node->analogRead = myAnalogRead ;
return TRUE ;
}