119 lines
4.1 KiB
C
119 lines
4.1 KiB
C
/*
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DHT-11 Library
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(c) Created by Charalampos Andrianakis on 18/12/11.
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Permission is hereby granted, free of charge, to any person obtaining a copy
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of this software and associated documentation files (the "Software"), to deal
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in the Software without restriction, including without limitation the rights
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to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
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copies of the Software, and to permit persons to whom the Software is
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furnished to do so, subject to the following conditions:
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The above copyright notice and this permission notice shall be included in
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all copies or substantial portions of the Software.
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THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
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AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
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OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
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THE SOFTWARE.
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*/
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#include <avr/io.h>
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#include "contiki.h"
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#include "dht11.h"
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#include "led.h" // debug
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#define udelay(u) clock_delay_usec(u)
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#define mdelay(u) clock_delay_msec(u)
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uint8_t DHT_Read_Data(uint8_t select){
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//data[5] is 8byte table where data come from DHT are stored
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//laststate holds laststate value
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//counter is used to count microSeconds
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uint8_t data[5], laststate = 0, counter = 0, j = 0, i = 0;
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//Clear array
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data[0] = data[1] = data[2] = data[3] = data[4] = 0;
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uint8_t volatile sreg;
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sreg = SREG; /* Save status register before disabling interrupts. */
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cli(); /* Disable interrupts. */
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//Prepare the bus
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PIN_INIT();
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//Set pin Output
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//Pin High
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DHT_DRIVE();
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mdelay(250); //Wait for 250mS
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//Send Request Signal
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//Pin Low
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OUTP_0();
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mdelay(20); //20ms Low
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//Pin High
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OUTP_1();
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udelay(40); //40us High
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//Set pin Input to read Bus
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//Set pin Input
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DHT_RELEASE();
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laststate=DHT_INP(); //Read Pin value
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//Repeat for each Transistions
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for (i=0; i<MAXTIMINGS; i++) {
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//While state is the same count microseconds
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while (laststate==DHT_INP()) {
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udelay(1);
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counter++;
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if (counter>254) break;
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}
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if (counter>254) break;
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//laststate==_BV(DHT_PIN) checks if laststate was High
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//ignore the first 2 transitions which are the DHT Response
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//if (laststate==_BV(DHT_PIN) && (i > 2)) {
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if ((i&0x01) && (i > 2)) {
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//Save bits in segments of bytes
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//Shift data[] value 1 position left
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//Example. 01010100 if we shift it left one time it will be
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//10101000
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led1_on();
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data[j/8]<<=1;
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if (counter >= 15) { //If it was high for more than 40uS
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led1_off();
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data[j/8]|=1; //it means it is bit '1' so make a logic
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led1_on();
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} //OR with the value (save it)
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j++; //making an OR by 1 to this value 10101000
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led1_off();
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} //we will have the resault 10101001
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//1 in 8-bit binary is 00000001
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//j/8 changes table record every 8 bits which means a byte has been saved
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//so change to next record. 0/8=0 1/8=0 ... 7/8=0 8/8=1 ... 15/8=1 16/8=2
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laststate=DHT_INP(); //save current state
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counter=0; //reset counter
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}
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SREG = sreg; /* Enable interrupts. */
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//Check if data received are correct by checking the CheckSum
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if (data[0] + data[1] + data[2] + data[3] == data[4]) {
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if (select==DHT_Temp) { //Return the value has been choosen
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return(data[2]);
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}else if(select==DHT_RH){
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return(data[0]);
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}
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}else{
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// uart_puts("\r\nCheck Sum Error");
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}
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return 0xff; // Check Sum Error
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}
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