ABOUT DHT22

RE: ABOUT DHT22

awneil — Thu, 11 Mar 2021 08:50:48 GMT

RE: ABOUT DHT22

MJ-K — Thu, 11 Mar 2021 07:30:22 GMT

I have resolved it by referring to this site.

Thank you for your answer!

RE: ABOUT DHT22

MJ-K — Thu, 11 Mar 2021 07:29:41 GMT

I have resolved it by referring to this site.

and 3.3V is possible.

Thank you for your answer!

RE: ABOUT DHT22

awneil — Tue, 09 Mar 2021 16:03:49 GMT

[quote userid="26071" url="~/f/nordic-q-a/72547/about-dht22/298758#298758"]It will probably be similar to the ds18b20 sensor[/quote]

Yes, the basic principle seems to be the same.

RE: ABOUT DHT22

Edvin — Tue, 09 Mar 2021 14:23:53 GMT

You would need to check the datasheet to make sure that it can run on the same voltage as the nRF, as awneil says.

The nRF doesn't have a physical one wire interface peripheral, so it needs to be bitbanged. It will probably be similar to the ds18b20 sensor, which a colleague of mine tested once, as described in this ticket. Please note that you would need to modify the driver from that example to match your sensor.

And finally, I really want to support awneil's point about making sure that this works before you start adding the complexity of doing this from a timer.

Also note that this may not work out of the box when you add the softdevice (for BLE), because bitbanging is very time sensitive, you may need to look into the Timeslot API to ensure that you have a timeslot where the softdevice will not interrupt you.

Best regards,

Edvin

RE: ABOUT DHT22

awneil — Tue, 09 Mar 2021 09:57:25 GMT

[quote userid="98449" url="~/f/nordic-q-a/72547/about-dht22"]I want to read the value of dht22 at regular intervals using the _timer_handle[/quote]

Before that, have you successfully managed to just read the DHT22 ?

There's no point adding the complication of a timer before you've got the basic reading working.

Note that this is a proprietary open-drain single-wire interface; it is similar to the Maxim (formerly Dallas) 1-Wire (TM), but not quite the same.

You are going to have to bit-bang it.

[quote userid="98449" url="~/f/nordic-q-a/72547/about-dht22"]How can I get the value?[/quote]

By following what the datasheet tells you: the device neither knows nor cares what microcontroller you use - you just have be sure that you implement whatever the datasheet tells you.

community.st.com/.../has-anyone-try-to-dht11-or-dht22-with-stm32f7-or-stm32h7

Did you note the issue in the linked thread that the DHT is a 5V device, but the nRF is only 3.3V ?