From 6ff78f802d3c8b14c225786625770887c0011c81 Mon Sep 17 00:00:00 2001
From: sheinz <shein@bk.ru>
Date: Wed, 6 Jul 2016 21:01:44 +0300
Subject: [PATCH] DHT11/DHT22 library fixes.

Fixed temperature below zero.
Fixed checksum overflow verification.
Fixed inconsistent reading of DHT11.
---
 examples/dht_sensor/dht_sensor.c | 8 ++++----
 extras/dht/dht.c                 | 7 ++++---
 2 files changed, 8 insertions(+), 7 deletions(-)

diff --git a/examples/dht_sensor/dht_sensor.c b/examples/dht_sensor/dht_sensor.c
index 46292da..425d5c0 100644
--- a/examples/dht_sensor/dht_sensor.c
+++ b/examples/dht_sensor/dht_sensor.c
@@ -15,7 +15,7 @@
  * to read and print a new temperature and humidity measurement
  * from a sensor attached to GPIO pin 4.
  */
-uint8_t const dht_gpio = 12;
+uint8_t const dht_gpio = 4;
 
 void dhtMeasurementTask(void *pvParameters)
 {
@@ -29,9 +29,9 @@ void dhtMeasurementTask(void *pvParameters)
 
     while(1) {
         if (dht_read_data(dht_gpio, &humidity, &temperature)) {
-            printf("Humidity: %d.%d%% Temp: %d.%dC\n", 
-                    humidity / 10, humidity % 10, 
-                    temperature / 10, abs(temperature) % 10);
+            printf("Humidity: %d%% Temp: %dC\n", 
+                    humidity / 10, 
+                    temperature / 10);
         } else {
             printf("Could not read data from sensor\n");
         }
diff --git a/extras/dht/dht.c b/extras/dht/dht.c
index cd84eba..3930735 100644
--- a/extras/dht/dht.c
+++ b/extras/dht/dht.c
@@ -64,13 +64,14 @@ static bool dht_await_pin_state(uint8_t pin, uint32_t timeout,
         bool expected_pin_state, uint32_t *duration)
 {
     for (uint32_t i = 0; i < timeout; i += DHT_TIMER_INTERVAL) {
+        // need to wait at least a single interval to prevent reading a jitter
+        sdk_os_delay_us(DHT_TIMER_INTERVAL);
         if (gpio_read(pin) == expected_pin_state) {
             if (duration) {
                 *duration = i;
             }
             return true;
         }
-        sdk_os_delay_us(DHT_TIMER_INTERVAL);
     }
 
     return false;
@@ -135,7 +136,7 @@ static inline int16_t dht_convert_data(uint8_t msb, uint8_t lsb)
     data = msb & 0x7F;
     data <<= 8;
     data |= lsb;
-    if (msb & BIT(15)) {
+    if (msb & BIT(7)) {
         data = 0 - data;       // convert it to negative
     }
 #elif DHT_TYPE == DHT11
@@ -169,7 +170,7 @@ bool dht_read_data(uint8_t pin, int16_t *humidity, int16_t *temperature)
         data[i/8] |= bits[i];
     }
 
-    if (data[4] != (data[0] + data[1] + data[2] + data[3])) {
+    if (data[4] != ((data[0] + data[1] + data[2] + data[3]) & 0xFF)) {
         debug("Checksum failed, invalid data received from sensor\n");
         return false;
     }