I replaced my car stereo with a Raspberry Pi 3 and the 7" touch screen. Everything's working nicely, but now I want to hook up the volume control buttons on the steering wheel to the Pi. The buttons work by changing the resistance across two wires in the stereo wiring harness. With no buttons pressed, the resistance is 10kΩ, volume up changes that to 300Ω, and volume down is 50Ω.
I have previously used an MCP3008 ADC to read resistance values with a Pi, however in that case I just polled the ADC as needed. In this case I think polling would take up too much CPU power for the sampling rate I need.
I have also previously used the Wiring Pi library to set up GPIO interrupts to detect rising and falling edges on voltage. My current plan is to use an interrupt to detect the change in voltage when I press a button, then use that to trigger a read from the ADC to get the precise resistance value.
My question is, is this a good way to do this, or is there something better?