From 92fc3e8bcba948e7ef02c9a7831cdf3765ae46ee Mon Sep 17 00:00:00 2001
From: UncleRus <unclerus@gmail.com>
Date: Mon, 22 Jul 2019 02:21:27 +0500
Subject: [PATCH] Support for Itead Si7021

---
 extras/dht/dht.c | 6 +++---
 extras/dht/dht.h | 3 ++-
 2 files changed, 5 insertions(+), 4 deletions(-)

diff --git a/extras/dht/dht.c b/extras/dht/dht.c
index dee04f2..34e7a07 100644
--- a/extras/dht/dht.c
+++ b/extras/dht/dht.c
@@ -81,14 +81,14 @@ static bool dht_await_pin_state(uint8_t pin, uint32_t timeout,
  * The function call should be protected from task switching.
  * Return false if error occurred.
  */
-static inline bool dht_fetch_data(uint8_t pin, bool bits[DHT_DATA_BITS])
+static inline bool dht_fetch_data(dht_sensor_type_t sensor_type, uint8_t pin, bool bits[DHT_DATA_BITS])
 {
     uint32_t low_duration;
     uint32_t high_duration;
 
     // Phase 'A' pulling signal low to initiate read sequence
     gpio_write(pin, 0);
-    sdk_os_delay_us(20000);
+    sdk_os_delay_us(sensor_type == DHT_TYPE_SI7021 ? 500 : 20000);
     gpio_write(pin, 1);
 
     // Step through Phase 'B', 40us
@@ -155,7 +155,7 @@ bool dht_read_data(dht_sensor_type_t sensor_type, uint8_t pin, int16_t *humidity
     gpio_enable(pin, GPIO_OUT_OPEN_DRAIN);
 
     taskENTER_CRITICAL();
-    result = dht_fetch_data(pin, bits);
+    result = dht_fetch_data(sensor_type, pin, bits);
     taskEXIT_CRITICAL();
 
     if (!result) {
diff --git a/extras/dht/dht.h b/extras/dht/dht.h
index 664e95c..3236902 100644
--- a/extras/dht/dht.h
+++ b/extras/dht/dht.h
@@ -21,7 +21,8 @@ extern "C" {
 typedef enum
 {
     DHT_TYPE_DHT11 = 0, //!< DHT11
-    DHT_TYPE_DHT22      //!< DHT22
+    DHT_TYPE_DHT22,     //!< DHT22
+    DHT_TYPE_SI7021     //!< Itead SI7021
 } dht_sensor_type_t;
 
 /**