151 lines
3.4 KiB
C
151 lines
3.4 KiB
C
/*
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* htu21d.c:
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* Extend wiringPi with the HTU21D I2C humidity and Temperature
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* sensor. This is used in the Pi Weather station.
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* Copyright (c) 2016 Gordon Henderson
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***********************************************************************
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* This file is part of wiringPi:
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* https://projects.drogon.net/raspberry-pi/wiringpi/
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*
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* wiringPi is free software: you can redistribute it and/or modify
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* it under the terms of the GNU Lesser General Public License as
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* published by the Free Software Foundation, either version 3 of the
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* License, or (at your option) any later version.
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*
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* wiringPi is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU Lesser General Public License for more details.
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*
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* You should have received a copy of the GNU Lesser General Public
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* License along with wiringPi.
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* If not, see <http://www.gnu.org/licenses/>.
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***********************************************************************
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*/
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#include <unistd.h>
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#include <stdint.h>
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#include <stdio.h>
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#include <math.h>
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#include "wiringPi.h"
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#include "wiringPiI2C.h"
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#include "htu21d.h"
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#define DEBUG
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#undef FAKE_SENSOR
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#define I2C_ADDRESS 0x40
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int checksum (uint8_t data [4])
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{
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return TRUE ;
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}
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/*
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* myAnalogRead:
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*********************************************************************************
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*/
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static int myAnalogRead (struct wiringPiNodeStruct *node, int pin)
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{
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int chan = pin - node->pinBase ;
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int fd = node->fd ;
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uint8_t data [4] ;
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uint32_t sTemp, sHumid ;
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double fTemp, fHumid ;
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int cTemp, cHumid ;
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/**/ if (chan == 0) // Read Temperature
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{
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// Send read temperature command:
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data [0] = 0xF3 ;
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if (write (fd, data, 1) != 1)
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return -9999 ;
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// Wait then read the data
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delay (50) ;
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if (read (fd, data, 3) != 3)
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return -9998 ;
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if (!checksum (data))
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return -9997 ;
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// Do the calculation
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sTemp = (data [0] << 8) | data [1] ;
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fTemp = -48.85 + 175.72 * (double)sTemp / 63356.0 ;
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cTemp = (int)rint (((100.0 * fTemp) + 0.5) / 10.0) ;
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return cTemp ;
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}
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else if (chan == 1) // humidity
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{
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// Send read humidity command:
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data [0] = 0xF5 ;
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if (write (fd, data, 1) != 1)
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return -9999 ;
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// Wait then read the data
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delay (50) ;
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if (read (fd, data, 3) != 3)
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return -9998 ;
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if (!checksum (data))
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return -9997 ;
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sHumid = (data [0] << 8) | data [1] ;
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fHumid = -6.0 + 125.0 * (double)sHumid / 65536.0 ;
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cHumid = (int)rint (((100.0 * fHumid) + 0.5) / 10.0) ;
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return cHumid ;
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}
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else
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return -9999 ;
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}
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/*
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* htu21dSetup:
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* Create a new instance of a HTU21D I2C GPIO interface.
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* This chip has a fixed I2C address, so we are not providing any
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* allowance to change this.
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*********************************************************************************
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*/
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int htu21dSetup (const int pinBase)
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{
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int fd ;
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struct wiringPiNodeStruct *node ;
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uint8_t data ;
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int status ;
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if ((fd = wiringPiI2CSetup (I2C_ADDRESS)) < 0)
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return FALSE ;
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node = wiringPiNewNode (pinBase, 2) ;
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node->fd = fd ;
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node->analogRead = myAnalogRead ;
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// Send a reset code to it:
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data = 0xFE ;
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if (write (fd, &data, 1) != 1)
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return FALSE ;
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delay (15) ;
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// Read the status register to check it's really there
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status = wiringPiI2CReadReg8 (fd, 0xE7) ;
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return (status == 0x02) ? TRUE : FALSE ;
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}
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