
// ****************************************************************************
//
//                                 Main code
//
// ****************************************************************************
// Measure temperature and humidity using DHT sensor.

#include "include.h"

const uint LED_PIN = PICO_DEFAULT_LED_PIN;
const uint DHT_PIN = 15;
const uint MAX_TIMINGS = 85;

typedef struct
{
	float humidity;
	float temp_celsius;
} dht_reading;

void read_from_dht(dht_reading *result);

int main()
{
	stdio_init_all();
	gpio_init(LED_PIN);
	gpio_init(DHT_PIN);
	gpio_set_dir(LED_PIN, GPIO_OUT);
	while (1)
	{
		dht_reading reading;
		read_from_dht(&reading);
		float fahrenheit = (reading.temp_celsius * 9 / 5) + 32;
		printf("Humidity = %.1f%%, Temperature = %.1fC (%.1fF)\n",
			reading.humidity, reading.temp_celsius, fahrenheit);

		sleep_ms(2000);
	}
}

void read_from_dht(dht_reading *result)
{
	int data[5] = {0, 0, 0, 0, 0};
	uint last = 1;
	uint j = 0;

	gpio_set_dir(DHT_PIN, GPIO_OUT);
	gpio_put(DHT_PIN, 0);
	sleep_ms(20);
	gpio_set_dir(DHT_PIN, GPIO_IN);

	gpio_put(LED_PIN, 1);
	for (uint i = 0; i < MAX_TIMINGS; i++)
	{
		uint count = 0;
		while (gpio_get(DHT_PIN) == last)
		{
			count++;
			sleep_us(1);
			if (count == 255) break;
		}
		last = gpio_get(DHT_PIN);
		if (count == 255) break;

		if ((i >= 4) && (i % 2 == 0))
		{
			data[j / 8] <<= 1;
			if (count > 16) data[j / 8] |= 1;
			j++;
		}
	}
	gpio_put(LED_PIN, 0);

	if ((j >= 40) && (data[4] == ((data[0] + data[1] + data[2] + data[3]) & 0xFF)))
	{
		result->humidity = (float) ((data[0] << 8) + data[1]) / 10;
		if (result->humidity > 100)
		{
			result->humidity = data[0];
		}
		result->temp_celsius = (float) (((data[2] & 0x7F) << 8) + data[3]) / 10;

		if (result->temp_celsius > 125)
		{
			result->temp_celsius = data[2];
		}

		if (data[2] & 0x80)
		{
			result->temp_celsius = -result->temp_celsius;
		}
	}
	else
	{
		printf("Bad data\n");
	}
}
