From 7df72ddb969bca32a72795e4137e01abe1b36f49 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Robin=20Smidsr=C3=B8d?= <robin@smidsrod.no>
Date: Tue, 19 May 2020 01:24:13 +0200
Subject: [PATCH] dht: Fix sensor reading from DHT22 (#926)

* dht: Fix sensor reading from DHT22 (#239)

Looking at the datasheet for DHT22, it claims to need a delay of 18ms, not
800us. Change to use the same delay as DHT11. Tested working with NodeMCUv3
and DHT22 sensor with board with built-in resistor.

* dht: Add model DHT22_TYPE2 with 2ms delay instead of 0.8ms

The model DHT22_TYPE2 is exactly the same as DHT22, but uses a different
delay.

* dht: Fix bogus negative temperature reading on DHT22_TYPE2

The workaround for negative numbers associated with DHT22s can be skipped
on these sensors.
---
 esphome/components/dht/dht.cpp   | 4 +++-
 esphome/components/dht/dht.h     | 4 +++-
 esphome/components/dht/sensor.py | 1 +
 3 files changed, 7 insertions(+), 2 deletions(-)

diff --git a/esphome/components/dht/dht.cpp b/esphome/components/dht/dht.cpp
index c311aa43ec..988a5300dd 100644
--- a/esphome/components/dht/dht.cpp
+++ b/esphome/components/dht/dht.cpp
@@ -92,6 +92,8 @@ bool HOT ICACHE_RAM_ATTR DHT::read_sensor_(float *temperature, float *humidity,
       delayMicroseconds(500);
       this->pin_->digital_write(true);
       delayMicroseconds(40);
+    } else if (this->model_ == DHT_MODEL_DHT22_TYPE2) {
+      delayMicroseconds(2000);
     } else {
       delayMicroseconds(800);
     }
@@ -208,7 +210,7 @@ bool HOT ICACHE_RAM_ATTR DHT::read_sensor_(float *temperature, float *humidity,
     uint16_t raw_humidity = (uint16_t(data[0] & 0xFF) << 8) | (data[1] & 0xFF);
     uint16_t raw_temperature = (uint16_t(data[2] & 0xFF) << 8) | (data[3] & 0xFF);
 
-    if ((raw_temperature & 0x8000) != 0)
+    if (this->model_ != DHT_MODEL_DHT22_TYPE2 && (raw_temperature & 0x8000) != 0)
       raw_temperature = ~(raw_temperature & 0x7FFF);
 
     if (raw_temperature == 1 && raw_humidity == 10) {
diff --git a/esphome/components/dht/dht.h b/esphome/components/dht/dht.h
index 4ed5d4e022..8826a3d2b7 100644
--- a/esphome/components/dht/dht.h
+++ b/esphome/components/dht/dht.h
@@ -12,7 +12,8 @@ enum DHTModel {
   DHT_MODEL_DHT22,
   DHT_MODEL_AM2302,
   DHT_MODEL_RHT03,
-  DHT_MODEL_SI7021
+  DHT_MODEL_SI7021,
+  DHT_MODEL_DHT22_TYPE2
 };
 
 /// Component for reading temperature/humidity measurements from DHT11/DHT22 sensors.
@@ -28,6 +29,7 @@ class DHT : public PollingComponent {
    *  - DHT_MODEL_AM2302
    *  - DHT_MODEL_RHT03
    *  - DHT_MODEL_SI7021
+   *  - DHT_MODEL_DHT22_TYPE2
    *
    * @param model The DHT model.
    */
diff --git a/esphome/components/dht/sensor.py b/esphome/components/dht/sensor.py
index 8455f74fb4..8749d85b52 100644
--- a/esphome/components/dht/sensor.py
+++ b/esphome/components/dht/sensor.py
@@ -15,6 +15,7 @@ DHT_MODELS = {
     'AM2302': DHTModel.DHT_MODEL_AM2302,
     'RHT03': DHTModel.DHT_MODEL_RHT03,
     'SI7021': DHTModel.DHT_MODEL_SI7021,
+    'DHT22_TYPE2': DHTModel.DHT_MODEL_DHT22_TYPE2,
 }
 DHT = dht_ns.class_('DHT', cg.PollingComponent)