I was sent a bunch of these humidity sensors for evaluation. Model DHT-11 made "overseas".
When queried the sensor sends back a 40 bit packet containing humidity data,
temperature data and a CRC. It uses a proprietary 1 wire protocol where.
1. A data 0 is a 26us pulse
2. A data 1 is a 70us pulse
3. Data bits are separated by a 50us "low" idle period.
The DHT-11 datasheet is here. http://www.robotshop.com/PDF/dht11.pdf
The attached diagram gives an example of the output
Question: Is is possible for an X2 Picaxe running at 64mhz to read and store this 40 bit packet ?
I'm guessing not possible due to the interpreter overhead and the short 50us idle time between bits.
However, someone out there smarter than I am may know how to get around the problem as I see it.
So far the best I can do is accurately count the bits using count while running the Picaxe at high speed.
Any suggestions would be appreciated.
Goey
When queried the sensor sends back a 40 bit packet containing humidity data,
temperature data and a CRC. It uses a proprietary 1 wire protocol where.
1. A data 0 is a 26us pulse
2. A data 1 is a 70us pulse
3. Data bits are separated by a 50us "low" idle period.
The DHT-11 datasheet is here. http://www.robotshop.com/PDF/dht11.pdf
The attached diagram gives an example of the output
Question: Is is possible for an X2 Picaxe running at 64mhz to read and store this 40 bit packet ?
I'm guessing not possible due to the interpreter overhead and the short 50us idle time between bits.
However, someone out there smarter than I am may know how to get around the problem as I see it.
So far the best I can do is accurately count the bits using count while running the Picaxe at high speed.
Any suggestions would be appreciated.
Goey
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