#include "main.h"
#include "generic_macros.h"
#include "lcd.h"
#include "DHT11.h"

extern TIM_HandleTypeDef htim2;

static void wait(uint32_t wait_us)
{
	uint32_t target_time = TIM2->CNT;
	target_time += wait_us << 4;

	while (TIM2->CNT < target_time) {}
}

static size_t dht11_measure_high_duration(void)
{
	uint32_t start_time = TIM2->CNT;
	SKIP_HIGH;
	uint32_t end_time = TIM2->CNT;

	// elapsed_time > 49us ? 1 : 0
	return (end_time - start_time) > (49 << 4);
}

static size_t dht11_read_value(struct DHT11_Data *data)
{
	// treat data as a normal array to simplify read loop
	uint8_t *buffer = (uint8_t *) data;

	register uint8_t read_register = 0;

	TIM2->CNT = 0;
	HAL_TIM_Base_Start(&htim2);

	GPIOD->MODER |= 0x00400000;      // enable output mode on GPIOD 11

	GPIOD->BSRR = GPIO_PIN_11;       // enable DHT11
	wait(18000);                     // hold HIGH for 18 ms
	GPIOD->BSRR = GPIO_PIN_11 << 16; // start signal
	wait(20);                        // hold it for 20 us
	GPIOD->BSRR = GPIO_PIN_11;       // pull up, DHT will now take control over the connection
	wait(40);

	GPIOD->MODER &= 0xFF3FFFFF;      // switch GPIOD 11 to input mode

	// reading transmission from DHT11
	SKIP_LOW;

	// waiting for 50 ms max
	for (size_t i = TIM2->CNT + (50000 << 4); TIM2->CNT >= i; )
		if (!(GPIOD->IDR & 0x0800))
			goto reading_data;

	// if didn't exit through goto, then DHT11 awaiting has timed out
	return 1;

reading_data:
	// read 5 bytes of data
	for (size_t i = 0; i < 5; i++) {
		for (register size_t j = 0; j < 8; j++) {
			read_register <<= 1;
			SKIP_LOW;
			read_register |= dht11_measure_high_duration();
		}

		buffer[i] = read_register;
	}

	HAL_TIM_Base_Stop(&htim2);

	return 0;
}

void DHT11_run_test(void)
{
	DISPLAY_CLEAR;
	display_write_data_seq("DHT11 Temp+Humid");

	struct DHT11_Data data;
	size_t result = dht11_read_value(&data);

	if (result == 1) {
		DISPLAY_SET_CURSOR(1, 1);
		display_write_data_seq("START TIMEOUT");
	} else {
		DISPLAY_SET_CURSOR(1, 1);
		display_write_data_seq("OK");
	}
}