79 lines
1.7 KiB
C
79 lines
1.7 KiB
C
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#include "config.h"
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#include <avr/io.h>
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#include <util/delay.h>
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#include <stdbool.h>
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#include "GDM1602K.h"
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#define DATAPIN PC0
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#define PORT PORTC
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#define PIN PINC
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#define DDR DDRC
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bool is_high() {
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return (PIN & (1 << DATAPIN));
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}
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// Function to read data from the DHT22 sensor
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int DHT22_Read(int *temperature, int *humidity)
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{
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// Set the data pin as output
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DDR |= (1 << DATAPIN);
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PORT |= (1 << DATAPIN); // Set the pin high, if not already pulled up
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_delay_ms(100);
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// Send start signal
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PORT &= ~(1 << DATAPIN); // Set the pin low
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_delay_us(500); // Hold it for a while
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PORT |= (1 << DATAPIN); // Set the pin high
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DDR &= ~(1 << DATAPIN); // Data direction in
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_delay_us(20); // Wait for 40 microseconds
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// Sensor should have pulled low here
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if(PIN & (1 << DATAPIN)) return -2;
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_delay_us(80); // Wait for 80 microseconds
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// Sensor should have pulled high here
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if(!(PIN & (1 << DATAPIN))) return -1;
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// Read data from the sensor
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uint8_t data[5] = {0, 0, 0, 0, 0};
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uint8_t bitMask = 0x80; // All zeroes with MSB high
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uint8_t byteIndex = 0;
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for (byteIndex = 0; byteIndex < 5; byteIndex++)
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{
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for (bitMask = 0x80; bitMask != 0; bitMask >>= 1)
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{
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// Wait for the data bit to go low
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while (!(PIN & (1 << PC0)))
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;
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// Wait for the data bit to go high
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_delay_us(20);
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if (PIN & (1 << PC0))
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data[byteIndex] |= bitMask;
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// Wait for the data bit to go low (end of bit)
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while (PIN & (1 << PC0))
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;
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}
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}
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// Verify checksum
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uint8_t checksum = data[0] + data[1] + data[2] + data[3];
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if (checksum != data[4])
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return -1;
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// Extract temperature and humidity
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*humidity = ((data[0] << 8) | data[1]);
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*temperature = ((data[2] << 8) | data[3]);
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return 0;
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}
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