dht_test/main.c

/*
 * This file is part of the libopencm3 project.
 *
 * Copyright (C) 2009 Uwe Hermann <uwe@hermann-uwe.de>
 *
 * This library is free software: you can redistribute it and/or modify
 * it under the terms of the GNU Lesser General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public License
 * along with this library.  If not, see <http://www.gnu.org/licenses/>.
 */

#include <stdio.h>

#include <libopencm3/cm3/nvic.h>
#include <libopencm3/stm32/rcc.h>
#include <libopencm3/stm32/gpio.h>
#include <libopencm3/stm32/timer.h>

#include <SEGGER_RTT.h>

#define DHT_PORT GPIOB
#define DHT_PIN  GPIO0

enum DHT11_STATE {
	DHT11_STOP,  // Stop statemachine
	DHT11_BEGIN_START,  // We drive DATA Low for min 18ms
	DHT11_END_START,  // We drive DATA High and set it to input
	DHT11_RESPONSE,  // Wait for DHT to drive DATA Low
	DHT11_DATA,
	DHT11_END
};

int g_dht11_state = DHT11_STOP;

int g_dht_i = 0;
uint16_t g_dht_vals[100] = {0};

static void delay(int count)
{
	for (int i=0; i < count; i++) {
		__asm__("nop");
	}
}

static void gpio_setup(void)
{
	/* Enable GPIOA clock. */
	/* Manually: */
	// RCC_APB2ENR |= RCC_APB2ENR_IOPCEN;
	/* Using API functions: */
	rcc_periph_clock_enable(RCC_GPIOB);

	/* Set GPIO5 (in GPIO port A) to 'output push-pull'. */
	/* Manually: */
	// GPIOA_CRH = (GPIO_CNF_OUTPUT_PUSHPULL << (((5 - 8) * 4) + 2));
	// GPIOA_CRH |= (GPIO_MODE_OUTPUT_2_MHZ << ((5 - 8) * 4));
	/* Using API functions: */
	gpio_set_mode(DHT_PORT, GPIO_MODE_INPUT, GPIO_CNF_INPUT_PULL_UPDOWN, DHT_PIN);
	gpio_set_mode(GPIOB, GPIO_MODE_OUTPUT_2_MHZ, GPIO_CNF_OUTPUT_PUSHPULL, GPIO1);
	gpio_set_mode(GPIOB, GPIO_MODE_OUTPUT_2_MHZ, GPIO_CNF_OUTPUT_PUSHPULL, GPIO2);
}

static void tim_setup(void)
{
	nvic_enable_irq(NVIC_TIM3_IRQ);
	nvic_set_priority(NVIC_TIM3_IRQ, 1);  // interrupts will not work without it???

	rcc_periph_clock_enable(RCC_TIM3);
	rcc_periph_reset_pulse(RST_TIM3);

	timer_set_mode(TIM3, TIM_CR1_CKD_CK_INT, TIM_CR1_CMS_EDGE, TIM_CR1_DIR_UP);
	timer_set_prescaler(TIM3, (rcc_apb1_frequency*2) / 1000000 - 1);  // set timer tickrate to 1mhz
	timer_set_period(TIM3, 0xffff);
	//timer_one_shot_mode(TIM3);

	timer_ic_set_input(TIM3, TIM_IC3, TIM_IC_IN_TI3);
	//timer_ic_set_filter(TIM3, TIM_IC3, 0b1111); // does not do anything ????
	//timer_ic_set_polarity(TIM3, TIM_IC3, TIM_IC_FALLING); // TIM_IC_RISING
	//timer_ic_enable(TIM3, TIM_IC3);

	timer_enable_irq(TIM3, TIM_DIER_UIE);
	timer_enable_irq(TIM3, TIM_DIER_CC1IE);  // triggered when DHT11_END_START
	timer_enable_irq(TIM3, TIM_DIER_CC3IE);  // triggered when DHT drives DATA pin

}

void tim3_isr(void)
{
	// Timer overflow that should only happen if DHT11 does not answer
	if (timer_get_flag(TIM3, TIM_SR_UIF)) {

		timer_clear_flag(TIM3, TIM_SR_UIF);
		//gpio_toggle(GPIOB, GPIO2);
		if (g_dht11_state == DHT11_RESPONSE) {
			puts("no response");
		} else if (g_dht11_state == DHT11_DATA) {
			puts("got data");
		} else {
			puts("overflow");
		}
		g_dht11_state = DHT11_STOP;
		timer_disable_counter(TIM3);

		//timer_set_counter(TIM3, 0);
		//timer_clear_flag(TIM3, TIM_SR_UIF);
		//timer_set_oc_value(TIM3, TIM_OC1, 1000);
	}

	// handle DHT11_END_START
	else if (timer_get_flag(TIM3, TIM_SR_CC1IF)) {
		timer_clear_flag(TIM3, TIM_SR_CC1IF);
		//gpio_toggle(GPIOB, GPIO2);
		if (g_dht11_state == DHT11_BEGIN_START) {
			g_dht11_state = DHT11_END_START;

			// And make the GPIO input so that we can wait for response
			gpio_set(DHT_PORT, DHT_PIN);
			gpio_set_mode(DHT_PORT, GPIO_MODE_INPUT, GPIO_CNF_INPUT_PULL_UPDOWN, DHT_PIN);

			// setup timer to wait for start response from dht11
			//timer_ic_set_polarity(TIM3, TIM_IC3, TIM_IC_FALLING);// TIM_IC_RISING
			timer_ic_set_polarity(TIM3, TIM_IC3, TIM_IC_RISING);// TIM_IC_RISING
			timer_ic_enable(TIM3, TIM_IC3);
			timer_clear_flag(TIM3, TIM_SR_CC3IF);
			//puts("waiting for response");
		}
		gpio_toggle(GPIOB, GPIO2);
	}

	else if (timer_get_flag(TIM3, TIM_SR_CC3IF))  // PB0 changed value
	{
		if (g_dht11_state == DHT11_END_START) {
			g_dht11_state = DHT11_RESPONSE;
			gpio_toggle(GPIOB, GPIO2);
			//timer_ic_disable(TIM3, TIM_IC3);
			//timer_clear_flag(TIM3, TIM_SR_CC3IF);
			//timer_ic_set_polarity(TIM3, TIM_IC3, TIM_IC_FALLING);// TIM_IC_RISING
			g_dht_vals[g_dht_i++] = TIM_CCR3(TIM3);				 // store captured high time value
			//timer_ic_enable(TIM3, TIM_IC3);
			gpio_toggle(GPIOB, GPIO2);
		} else {
			gpio_toggle(GPIOB, GPIO2);
			g_dht11_state = DHT11_DATA;
			g_dht_vals[g_dht_i] = TIM_CCR3(TIM3) - g_dht_vals[g_dht_i-1]; // store length from last sample
			g_dht_i++;
			gpio_toggle(GPIOB, GPIO2);
		}

//		if (timer_get_flag(TIM3, TIM_SR_CC3OF))
//		{
//			timer_clear_flag(TIM3, TIM_SR_CC3OF);
//			puts("we are too slow to read and clear timer input capture flags");
//		}
	}

}

static void dht_start(void)
{
	timer_disable_counter(TIM3);
	g_dht11_state = DHT11_BEGIN_START;
	g_dht_i = 0;

	// Setup DHT11_END_START trigger on output compare 1
	timer_set_counter(TIM3, 0);
	timer_set_oc_value(TIM3, TIM_OC1, 1000*20);  // 20ms
	timer_clear_flag(TIM3, TIM_SR_CC1IF);

	// Do DHT11_BEGIN_START aka drive DATA Low
	gpio_set_mode(DHT_PORT, GPIO_MODE_OUTPUT_2_MHZ, GPIO_CNF_OUTPUT_PUSHPULL, DHT_PIN);
	gpio_clear(DHT_PORT, DHT_PIN);

	// And start counting
	timer_enable_counter(TIM3);

	//gpio_toggle(GPIOB, GPIO2);

}

static void dht_start_signal(void)
{
	gpio_set_mode(DHT_PORT, GPIO_MODE_OUTPUT_2_MHZ, GPIO_CNF_OUTPUT_PUSHPULL, DHT_PIN);
	gpio_clear(DHT_PORT, DHT_PIN);
	delay(100000);
	//delay(30000);
	gpio_set(DHT_PORT, DHT_PIN);
	delay(100);
	gpio_set_mode(DHT_PORT, GPIO_MODE_INPUT, GPIO_CNF_INPUT_PULL_UPDOWN, DHT_PIN);
}

int main(void)
{
	int i = 0;
	puts("Start");
	rcc_clock_setup_pll(&rcc_hse_configs[RCC_CLOCK_HSE8_72MHZ]);
	gpio_setup();
	tim_setup();

	/* Blink the LED (PA5) on the board. */
	while (1) {
		/* Using API function gpio_toggle(): */
		gpio_toggle(GPIOB, GPIO1);	/* LED on/off */
		delay(10000000);
		dht_start();

		i++;
		SEGGER_RTT_printf(0, "Poll: %d\n", i);
	}

	return 0;
}