Removed "End the start signal by setting data line high for 40 micros… #51
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Closed
vlad-sh
reviewed
Sep 20, 2016
| // therefore the low-high transition after the start signal "low" needs to be realised by | ||
| // the pullup resistor only, uC pin must already be in INPUT mode. | ||
| // ref: https://github.com/adafruit/DHT-sensor-library/issues/48#issue-119801608 | ||
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| // Now start reading the data line to get the value from the DHT sensor. | ||
| pinMode(_pin, INPUT_PULLUP); | ||
| delayMicroseconds(10); // Delay a bit to let sensor pull data line low. |
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I found out there are must be some "smart" delay instead delayMicroseconds(10):
pinMode(_pin, INPUT_PULLUP); delayMicroseconds(10); // Delay a bit to let sensor pull data line low.
The delay may be like:
if (expectPulse(HIGH) == 0) { DEBUG_PRINTLN(F("Timeout waiting for start signal high pulse.")); _lastresult = false; return _lastresult; }
If no delay, next expectPulse(LOW) function often returns 0, because _pin is still HIGH (sensor takes from 20 to 200 microseconds to pull-down line to LOW, according datasheet).
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…econds"
Reference: #48 (comment)
@w-h many thanks for this fix!