too many DHTXX devices ?

Toit

#too many DHTXX devices ?

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kaxori 03/14/2025 11:06 AM

For plant cultivation, I would like to use several DHTxx sensors to check the favorable germination environment. The prototype uses an ESP32 'wroom'. Four sensors can be configured in the application. An exception error is generated when initializing the fifth sensor:

EXCEPTION error.
ALREADY_IN_USE
   0: gpio-use_                 <sdk>\gpio\gpio.toit:855:5

The Toit DHTxx package uses RMT-devices.

ESP32 shout provide 8 RMT channels.
Is it possible to use more than 4 devices on an ESP32-Wroom ?

floitsch 03/14/2025 11:07 AM

We are using two RMT channels per device. One for reading and one for writing. And they have to run at the same time...

floitsch 03/14/2025 11:08 AM

You could just close the ones you are currently not using and just run through them one by one

kaxori 03/14/2025 11:09 AM

that explains it

floitsch 03/14/2025 11:09 AM

The protocol of the dht is also slow enough that it works in software. Not super reliably, but still.

floitsch 03/14/2025 11:11 AM

Fwiw I prefer the ds18b20 (temperature only) and the bmw280 (i2c).

kaxori 03/14/2025 11:11 AM

Thank You, I will try to close the channels after use.

kaxori 03/14/2025 11:42 AM

It works !

close: //driver.close: not implemented
    driver.channel-in_.close
    driver.channel-out_.close

has caused it:

- DHTXX-1: T:22.4 °C, H:28.1 %, Habs: 5.6 g/m^3
 - DHTXX-2: T:23.3 °C, H:29.7 %, Habs: 6.2 g/m^3
 - DHTXX-3: T:19.7 °C, H:92.1 %, Habs:15.6 g/m^3
 - DHTXX-4: T:20.0 °C, H:74.2 %, Habs:12.8 g/m^3
 - DHTXX-5: T:19.9 °C, H:99.9 %, Habs:17.2 g/m^3
 - DHTXX-6: T:19.2 °C, H:67.6 %, Habs:11.1 g/m^3
 - DHTXX-7: T:19.3 °C, H:65.4 %, Habs:10.8 g/m^3
 - DHTXX-8: T:19.9 °C, H:58.0 %, Habs:10.0 g/m^3

floitsch 03/14/2025 12:14 PM

you are right: we forgot to implement close.
I will do that. Thanks.

floitsch 03/14/2025 12:20 PM

v1.6.0 has been released.
if you update the dhtxx driver you should be able to just call driver.close.

kaxori 03/14/2025 12:35 PM

faster than lightning strikes !

kaxori 03/14/2025 05:49 PM

Feel free to use the example:
https://github.com/kaxori/Multiple-DHTxx-sensor-example

GitHub - kaxori/Multiple-DHTxx-sensor-example

Contribute to kaxori/Multiple-DHTxx-sensor-example development by creating an account on GitHub.

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