Dear community,
does anyone has MQ135 connected to an A20? Did already someone write a driver for reading the digital value?
best regards,
Markus
Seems like the information "the digital output is frequency related to the output value" from https://olimex.wordpress.com/2015/05/26/experimenting-with-gas-sensors-and-arduino/ is wrong. So my previous question is probably irrelevant as the driver would be trivial.
Anyway, I did not investigate it further and now use the analog interface via an Arduino. It allows me to use 12 sensors without any additional hardware.
best regards,
Markus