126 lines
4.1 KiB
C
126 lines
4.1 KiB
C
/*
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* File: main.c
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* Author: clement
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*
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* Created on July 14, 2025, 3:54 PM
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*/
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#include <stdio.h>
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#include <stdlib.h>
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#include <xc.h>
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// Configuration bits
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#pragma config FOSC = INTOSC // Oscillator Selection bits (INTOSC oscillator: I/O function on CLKIN pin)
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#pragma config WDTE = OFF // Watchdog Timer Enable (WDT disabled)
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#pragma config PWRTE = OFF // Power-up Timer Enable (PWRT disabled)
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#pragma config MCLRE = ON // MCLR Pin Function Select (MCLR/VPP pin function is digital input)
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#pragma config CP = OFF // Flash Program Memory Code Protection (Program memory code protection is disabled)
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#pragma config BOREN = OFF // Brown-out Reset Enable (Brown-out Reset disabled)
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#pragma config CLKOUTEN = OFF // Clock Out Enable (CLKOUT function is disabled. I/O or oscillator function on the CLKOUT pin)
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#pragma config LVP = OFF
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#pragma config DEBUG = ON
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#pragma config PLLEN = 0
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// Pins define
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#define DHT22_PIN_DIR TRISAbits.TRISA4
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#define DHT22_DATA PORTAbits.RA4
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#define CTRL_1 PORTAbits.RA5
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#define CTRL_2 PORTAbits.RA2
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// Clock frequency (used for __delay_xx)
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#define _XTAL_FREQ 8000000
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// Utils macro for waiting a pin state for DHT22_DATA, returning 1 if timed out.
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#define waitDHTOrRet(up) TMR0 = 0; while(DHT22_DATA != (up)){ if(TMR0 > 240) return 1; }
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uint8_t dhtBytes[5]; // 2 first bytes: humidity, 2 following: temperature, 5th: checksum
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// Reads the DHT, returns 0 if error
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int readDHT() {
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// Empty old payload
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for(uint8_t i = 0; i < 5; i++){
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dhtBytes[i] = 0;
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}
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// Wait for an old payload eventually aborted to end (lasts about 4ms)
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__delay_ms(5);
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// Sends the start signal: low for at least 1ms, then high for 20 to 40us
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DHT22_PIN_DIR = 0; // configure as output, then set it as 0 (= LATAbits.LATA4).
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__delay_ms(2);
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DHT22_PIN_DIR = 1; // configure as input, then set it as 1 (through pullup).
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__delay_us(40);
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// Check DHT start response
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waitDHTOrRet(0); // DHT pulls low
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waitDHTOrRet(1); // DHT pulls high for 80ms
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__delay_us(40);
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waitDHTOrRet(0); // DHT pulls low
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// Read the 5 DHT payload bytes in dhtBytes
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for (uint8_t n = 0; n < 5; n++) {
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for (int8_t i = 7; i >= 0; i--) {
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waitDHTOrRet(1); // Wait for up
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CTRL_1 = 1;
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waitDHTOrRet(0); // Wait for low. Waited time is TMR0.
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CTRL_1 = 0;
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if (TMR0 > 50) { // Low: 26-28us High: 70us
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dhtBytes[n] |= 1 << i;
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}
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}
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}
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return 0;
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}
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// Fetches humidity & temp from DHT, returns 0 if error
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int fetchClimate(int8_t* humidity, int8_t* temperature) {
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if(readDHT()) return 1;
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uint8_t checksum = dhtBytes[0] + dhtBytes[1] + dhtBytes[2] + dhtBytes[3];
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if (dhtBytes[4] != checksum) {
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return 1; // Checksum error
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}
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uint16_t hum = (((uint16_t) (dhtBytes[0])) << 8) | ((uint16_t) dhtBytes[1]);
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*humidity = (int8_t) (hum / 10);
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uint16_t temp = (((uint16_t) (dhtBytes[2])) << 8) | ((uint16_t) dhtBytes[3]);
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int8_t tempRound = (temp % 10) >= 5 ? 1 : 0;
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if (temp & 0x8000) { // If high bit is 1, temperature is negative.
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*temperature = - (int8_t) ((temp & 0x7FFF) / 10) - tempRound;
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}else {
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*temperature = (int8_t) (temp / 10) + tempRound;
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}
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return 0;
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}
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void main() {
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// 8MHz internal clock
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OSCCON = 0b01110000;
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// Ping config
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TRISA = 0b11011011; // Declare RA2 and RA5 as output (bit = 0)
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ANSELA = 0b00000011; // Declare used pins as digital I/O (bit = 0)
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WPUA = 0b00010000; // Active la r<>sistance de pull-up sur RA4
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LATAbits.LATA4 = 0; // Declare RA4 output value as 0 (only effective when DHT22_PIN_DIR = 0)
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// Timer 0 config
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OPTION_REGbits.PSA = 0; // Enable prescaler
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OPTION_REGbits.PS = 0b000; // 1/2 prescaler
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OPTION_REGbits.TMR0CS = 0; // Use internal clock
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OPTION_REGbits.TMR0SE = 0; // Increment on rising edge
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while (1) {
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int8_t hum = 0;
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int8_t temp = 0;
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int is_error = fetchClimate(&hum, &temp);
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if(is_error){
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__delay_ms(5000);
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}
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__delay_ms(200);
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}
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}
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