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Pull high at end of start signal is too long #18

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gmpetro opened this issue Oct 12, 2024 · 1 comment
Open

Pull high at end of start signal is too long #18

gmpetro opened this issue Oct 12, 2024 · 1 comment

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@gmpetro
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gmpetro commented Oct 12, 2024

Hi,

thanks for providing this library. I found an issue: At the end of the start signal you wait for 40us before you release the pin, but the DHT11 (at least mine) pulls down the pin already after some 12us leading to a brief period of short circuit, which is not good.
Actually it would be sufficient to pull the pin actively high for 1 or 2us and leave the rest to the pull-up resistor.

I atteched a scope screen shot of the issue. We see the signal pulled high to 5V, then after 12us the DHT11 tries to pull it low, but the Arduino is still driving, so some intermediate voltage builds up (here 3V). After 42us - here's that number again ;-) - the Arduino releases the pin and the line is pulled further down by the DHT11, which is still driving.

Maybe you may want to fix this.
Thanks, Gerhard
scope_50

@raphaelobinna
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I have created a pull request to accommodate for you to set your own custom high signal delay, i hope this resolves your issue. here

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