From 1c587d5ba36db5da014c90296aed4e55014833fc Mon Sep 17 00:00:00 2001
From: Arti Zirk <arti.zirk@gmail.com>
Date: Thu, 8 Jul 2021 01:02:05 +0300
Subject: [PATCH] Works!

---
 main.c | 67 ++++++++++++++++++++++++++++++++++++++++++++++++----------
 1 file changed, 56 insertions(+), 11 deletions(-)

diff --git a/main.c b/main.c
index 997ec80..81031ed 100644
--- a/main.c
+++ b/main.c
@@ -34,14 +34,15 @@ enum DHT11_STATE {
 	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
+	DHT11_DATA,  // Receiving data
+	DHT11_END,  // Got last bit
+	DHT11_TIMEOUT,  // Not response or data got
 };
 
 int g_dht11_state = DHT11_STOP;
 
 int g_dht_i = 0;
-uint16_t g_dht_vals[100] = {0};
+uint16_t g_dht_vals[43] = {0};
 
 static void delay(int count)
 {
@@ -106,7 +107,7 @@ void tim3_isr(void)
 		} else {
 			puts("overflow");
 		}
-		g_dht11_state = DHT11_STOP;
+		g_dht11_state = DHT11_TIMEOUT;
 		timer_disable_counter(TIM3);
 
 		//timer_set_counter(TIM3, 0);
@@ -127,7 +128,6 @@ void tim3_isr(void)
 
 			// setup timer to wait for start response from dht11
 			timer_ic_set_polarity(TIM3, TIM_IC3, TIM_IC_FALLING);
-			//timer_ic_set_polarity(TIM3, TIM_IC3, TIM_IC_RISING);// TIM_IC_RISING
 			timer_clear_flag(TIM3, TIM_SR_CC3IF);
 			timer_ic_enable(TIM3, TIM_IC3);
 			//puts("waiting for response");
@@ -144,17 +144,23 @@ void tim3_isr(void)
 			//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
+			//timer_ic_set_polarity(TIM3, TIM_IC3, 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++;
+			g_dht_vals[g_dht_i++] = TIM_CCR3(TIM3); // store length from last sample
 			//gpio_toggle(GPIOB, GPIO2);
 		}
+
+		if (g_dht_i > 41) {
+			// we have the whole packet
+			g_dht11_state = DHT11_END;
+			timer_disable_counter(TIM3);
+		}
+
 		timer_clear_flag(TIM3, TIM_SR_CC3IF);
 		gpio_toggle(GPIOB, GPIO2);
 
@@ -192,6 +198,35 @@ static void dht_start(void)
 
 }
 
+static void dht_parse_data(){
+	int8_t data[5] = {0};
+	uint8_t checksum = 0;
+	int data_index = 0;
+	int data_bit = 7;
+	for (int i=2; i < 42; i++){  // First 2 pulses are start of response, ignore them
+		uint16_t bit_time = g_dht_vals[i] - g_dht_vals[i-1];
+		if (bit_time > 100) {
+			data[data_index] |= 1 << data_bit;
+		}
+		data_bit--;
+		if (data_bit < 0) {
+			data_bit = 7;
+			data_index++;
+		}
+	}
+
+	for (int i = 0; i < 4; i++){
+		checksum += data[i];
+	}
+
+	if (checksum == data[4]) {
+		SEGGER_RTT_printf(0, "Humidity: %d.%d%%; Temperature: %d.%dC\n",
+						  data[0], data[1], data[2], data[3]);
+	} else {
+		SEGGER_RTT_printf(0, "Checksum did not match, %x != %x\n", checksum, data[4]);
+	}
+}
+
 static void dht_start_signal(void)
 {
 	gpio_set_mode(DHT_PORT, GPIO_MODE_OUTPUT_2_MHZ, GPIO_CNF_OUTPUT_PUSHPULL, DHT_PIN);
@@ -206,6 +241,7 @@ static void dht_start_signal(void)
 int main(void)
 {
 	int i = 0;
+	bool wait = false;
 	puts("Start");
 	rcc_clock_setup_pll(&rcc_hse_configs[RCC_CLOCK_HSE8_72MHZ]);
 	gpio_setup();
@@ -215,11 +251,20 @@ int main(void)
 	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);
+		delay(10000000);
+		dht_start();
+		wait = true;
+		while (wait) {
+			switch (g_dht11_state) {
+				case DHT11_END:
+					dht_parse_data();
+					// fall through
+				case DHT11_TIMEOUT:
+					wait = false;
+			}
+		}
 	}
 
 	return 0;