I am designing a board (Main PCB) into which any one of about 60 slightly different boards (Peripheral PCB) may be connected/plugged-in.
The challenge I'm facing is to autonomously identify which of the Peripheral boards is plugged in at any given time.
The Main PCB has a microcontroller available to do some processing.
However, to minimize part count, the Peripheral PCBs each have only a (unique) sensor, and no intelligence -- i.e., no microcontroller on board, e.g., to send information via digital pins or I2C -- as of now .
Both boards are open to design changes, although the inter-connector pin count leaves me at the moment with only two more free pins available to use for any further modification.
What is the simplest, least expensive way (< $1 USD) I can modify the circuits to let the Main PCB identify which of the Peripheral PCBs is plugged in?
Will I have to add a microcontroller to each Peripheral PCB, or is there a smarter way?
ADC reading of a unique voltage divider on each Peripheral board seemed like a good start but for such a large number of different boards to be identified, this does not seem like a very reliable strategy.