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dht: Fix sensor reading from DHT22 (#926)

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* 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.
This commit is contained in:
Robin Smidsrød
2020-05-19 01:24:13 +02:00
committed by GitHub
parent 1d9ce2afc5
commit 7df72ddb96
3 changed files with 7 additions and 2 deletions
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4
esphome/components/dht/dht.cpp
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@@ -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) {