From 7cb17713d731eec4eb5dc6b34ecb7ad31809eaf4 Mon Sep 17 00:00:00 2001
From: Theo Arends <11044339+arendst@users.noreply.github.com>
Date: Sun, 14 Feb 2021 12:03:49 +0100
Subject: [PATCH] Refactor DHT negative temps

---
 tasmota/xsns_06_dht.ino | 27 +++++++++++++++++++++++----
 1 file changed, 23 insertions(+), 4 deletions(-)

diff --git a/tasmota/xsns_06_dht.ino b/tasmota/xsns_06_dht.ino
index c9eec0955..3abfd001a 100644
--- a/tasmota/xsns_06_dht.ino
+++ b/tasmota/xsns_06_dht.ino
@@ -157,14 +157,33 @@ bool DhtRead(uint32_t sensor)
   float temperature = NAN;
   float humidity = NAN;
   switch (Dht[sensor].type) {
-    case GPIO_DHT11:
+    case GPIO_DHT11:                                    // DHT11
       humidity = dht_data[0];
+/*
+      // DHT11 no negative temp:
       temperature = dht_data[2] + ((float)dht_data[3] * 0.1f);  // Issue #3164
+*/
+      // DHT11 (Adafruit):
+      temperature = dht_data[2];
+      if (dht_data[3] & 0x80) {
+        temperature = -1 - temperature;
+      }
+      temperature += (dht_data[3] & 0x0f) * 0.1f;
+/*
+      // DHT12 (Adafruit):
+      temperature = dht_data[2];
+      temperature += (dht_data[3] & 0x0f) * 0.1f;
+      if (dht_data[2] & 0x80) {
+        temperature *= -1;
+      }
+*/
       break;
-    case GPIO_DHT22:
-    case GPIO_SI7021:
+    case GPIO_DHT22:                                    // DHT21, DHT22, AM2301, AM2302, AM2321
+    case GPIO_SI7021:                                   // iTead SI7021
       humidity = ((dht_data[0] << 8) | dht_data[1]) * 0.1;
-      temperature = (((dht_data[2] & 0x7F) << 8 ) | dht_data[3]) * 0.1;
+      // DHT21/22 (Adafruit):
+      temperature = ((int16_t)(dht_data[2] & 0x7F) << 8 ) | dht_data[3];
+      temperature *= 0.1f;
       if (dht_data[2] & 0x80) {
         temperature *= -1;
       }