Copied from sourcehut.

1 files changed, 121 insertions, 0 deletions

diff --git a/main/dht.c b/main/dht.c
new file mode 100644
index 0000000..669f797
--- /dev/null
+++ b/main/dht.c
@@ -0,0 +1,121 @@
+Copyright (c) 2015, SuperHouse Automation Pty Ltd
+Copyright (c) 2016, Jonathan Hartsuiker (https://github.com/jsuiker)
+Copyright (c) 2019, Fonger (https://github.com/fonger)
+
+#include <freertos/FreeRTOS.h>
+#include <freertos/task.h>
+
+#include <driver/gpio.h>
+#include <esp8266/gpio_struct.h>
+#include <rom/ets_sys.h>
+#include <esp_log.h>
+
+#include "dht.h"
+
+#define DHT_PIN GPIO_NUM_2 
+#define DHT_DATA_LEN 40
+
+static const char *tag = "dht";
+
+static inline int dht_get_pin_state()
+{
+	return (GPIO.in >> DHT_PIN) & 0x1;
+}
+
+static inline int dht_await_pin_state(int state, int timeout)
+{
+	int t;
+	static const uint16_t delta = 1;
+
+	for (t = 0; t < timeout; t += delta) {
+		os_delay_us(delta);
+		if (dht_get_pin_state() == state)
+			return t;
+	}
+	return 0;
+}
+
+static inline int dht_get_raw_data(uint8_t buf[DHT_DATA_LEN])
+{
+	uint8_t i, pwl, pwh;
+
+	gpio_set_level(DHT_PIN, 0);
+	os_delay_us(1100);
+	gpio_set_level(DHT_PIN, 1);
+
+	if (!dht_await_pin_state(0, 40)) {
+		ESP_LOGI(tag, "start sequence phase 1 error");
+		return 0;
+	}
+	if (!dht_await_pin_state(1, 80)) {
+		ESP_LOGI(tag, "start sequence phase 2 error");
+		return 0;
+	}
+	if (!dht_await_pin_state(0, 80)) {
+		ESP_LOGI(tag, "start sequence phase 3 error");
+		return 0;
+	}
+
+	for (i = 0; i < DHT_DATA_LEN; i++) {
+		if (!(pwl = dht_await_pin_state(1, 50))) {
+			ESP_LOGI(tag, "low bit timed out");
+			return 0;
+		}
+		if (!(pwh = dht_await_pin_state(0, 70))) {
+			ESP_LOGI(tag, "high bit timed out");
+			return 0;
+		}
+		buf[i] = pwh > pwl;
+	}
+	return 1;
+}
+
+static inline int dht_verify_checksum(const uint8_t data[5])
+{
+	return data[4] == ((data[0] + data[1] + data[2] + data[3]) & 0xFF);
+}
+
+int16_t dht_decode_data(uint8_t msb, uint8_t lsb)
+{
+	int16_t x;
+
+	x = msb & 0x7F; 
+	x <<= 8;
+	x |= lsb;
+	if (msb >> 7)
+		x = 0 - x;
+	return x;
+} 
+
+int dht_get_data(uint8_t result[5])
+{
+	uint8_t i, rc, buf[DHT_DATA_LEN];
+	
+	vPortETSIntrLock();
+	rc = dht_get_raw_data(buf);
+	vPortETSIntrUnlock();
+	
+	if (rc) {
+		for (i = 0; i < DHT_DATA_LEN; i++) {
+			result[i / 8] <<= 1;
+			result[i / 8] |= buf[i];
+		}
+		if (dht_verify_checksum(result))
+			return 1;
+		else
+			ESP_LOGI(tag, "checksum failed");
+	}
+	return 0;
+}
+
+void dht_init(void)
+{
+	gpio_config_t io_conf;
+
+	io_conf.pin_bit_mask = 1UL << DHT_PIN;
+	io_conf.mode = GPIO_MODE_OUTPUT_OD;
+	gpio_config(&io_conf);
+	gpio_set_level(DHT_PIN, 1);
+
+	vTaskDelay(1000 / portTICK_PERIOD_MS);
+}