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Decode DHT11 decimal part (#861)

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* Decode DHT11 decimal part

* Fix comment

* Fix comment

* Handle negative temp for some DHT11  - code from the DHT12 component

* Don't use the fractional part if the checksum is the 2 bytes one
This commit is contained in:
Airy André 2019-11-20 17:00:32 +01:00 committed by Otto Winter
parent ad76709d00
commit b7b23ffdb2
1 changed files with 18 additions and 4 deletions
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20
esphome/components/dht/dht.cpp
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@ -165,10 +165,24 @@ bool HOT DHT::read_sensor_(float *temperature, float *humidity, bool report_erro
}
if (this->model_ == DHT_MODEL_DHT11) {
*humidity = data[0];
if (*humidity > 100)
*humidity = NAN;
if (checksum_a == data[4]) {
// Data format: 8bit integral RH data + 8bit decimal RH data + 8bit integral T data + 8bit decimal T data + 8bit
// check sum - some models always have 0 in the decimal part
const uint16_t raw_temperature = uint16_t(data[2]) * 10 + (data[3] & 0x7F);
*temperature = raw_temperature / 10.0f;
if ((data[3] & 0x80) != 0) {
// negative
*temperature *= -1;
}
const uint16_t raw_humidity = uint16_t(data[0]) * 10 + data[1];
*humidity = raw_humidity / 10.0f;
} else {
// For compatibily with DHT11 models which might only use 2 bytes checksums, only use the data from these two
// bytes
*temperature = data[2];
*humidity = data[0];
}
} else {
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);