How Can Rpi3B+ Detect MQ9 Gas Sensor's Carbon Monoxide Leakage,
Without Using ADC?
Understanding MQ9's Digital and Analog signals
MQ9 has both a Digital and an Analog output signal, as summarized below:
(a) Digital - To detect gas leakage or no leakage, outputting High level 4.8V, or Low, 0.2V, respectively.
(b) Analog - ...