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nico

DHT22 in a NanoPi M1

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Hi! I just bought a NanoPi M1 board and It is running with Armbian without problem. Now I want to add a DHT22 temp & hum sensor but searching in the web I cant find any script to get it work. I saw that the RPi script doesn't work on the NanoPi M1 because the chip is differnt. In the Friendlyarm page there is a C script to work with the DHT11, but nothing with the DHT22. So, anyone have been experimenting whit it in this context? There are a Wiring Pi equivalent to NanoPi M1? Thanks

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Tkaiser, thanks you for your soon answer. I read the post you mentioned and follow the LeMaker's steps (https://github.com/LeMaker/WiringBP) but it doesn't work for the NanoPi. Then I found this blog WiringPi in a Orange Pi with which I have more hope since Orange Pi PC has the same AllWinnwer H3 processor, but it doesn't work either, I do not have many clues why.

Finally, I found in the FriendlyARM Wiki the procedure to install a DHT11 sensor in a NanoPi M1 with a Debian OS, which consists in the installation of only one library. I tested it in Armbian and it doesn't work. As last test, I booted the NanoPi with Debian image and tested the FriendlyARM library and it works! but only with a DHT11 sensor, not the case with the DHT22. So, I'm a little confused by all this, especially since it should have worked with the Orange Pi procedure. Any tips?

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Its Works! Like Yudanta referenced is his blog, Pete was experimenting with the NanoPi and after I read his article, I realiced that I was looking the wrong PIN. I got the DHT22 working using this WiringPi but with some errors each 5 or 6 readings. I used the Yudanta referened driver and the Tkaiser driver but with both I have random reading errors. I'll investigate in deep later. Thank you very much!

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You can try this project for DHT22 : https://github.com/technion/lol_dht22

I made some modifications here : https://github.com/seblucas/lol_dht22and I've been using it for a year and a half on my Banana Pi doing a reading every 15 minutes. So far I loose on average 1 reading per day.

 

You can see here that the program has to wait for specific amount of time. So if you want to use your DHT22 with a lot of reliability, you'll have to keep the CPU load low and maybe tweak your cpufreq settings to set a minimal freq at around 600MHz this should help lowering the errors you see.

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vlad59: thanks for the tips! i will test lol_dht22 driver.

To learn, why lowering the frequency the reliability is better?

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I've advised to change the minimal frequency to an higher value (not lower) : 600MHz instead of 480MHz

 

That's mainly because delayMicroseconds is a busy loop so having an higher frequency will make it more precise. Linux is not a realtime OS so you don't have much choice.

 

Of course if you need 100% reliability, your best choice is to connect your DHT22 to an Arduino and connect your Arduino to your Orange Pi with an UART.

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Of course if you need 100% reliability, your best choice is to connect your DHT22 to an Arduino and connect your Arduino to your Orange Pi with an UART.

 

Since the normal use case for DHT11/DHT22 is monitoring minor changes over time (both temperature and humidity only slightly change) one can also simply use a software approach. Simply drop readouts with wrong checksum and use the last value known.

 

This is a Lamobo R1 (also A20) allowed to clock between 144 and 912 MHz. The only busy times are throughout the day when 5 RPi acting as surveillance cameras stream to the Lamobo (then cpufreq is between 720 and 912 MHz, all the other times at 144 MHz). Also I saved the 4k7 resistor so I get really often readout fails but it doesn't really matter at all since all I wanted to know is whether the 3 already available temperature sensors inside the enclosure (A20, AXP209 and Samsung SATA disk queried through SMART) work correctly -- obviously they do:

 

Bildschirmfoto%202016-08-04%20um%2010.29

 

Bildschirmfoto%202016-08-04%20um%2010.36

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