Identify which sensor is connected

[stelios26]

Dear all,

First of all hello, this is my first post in these forums.

Straight to the point. I am developing a small robotic interface for a small toy (kind of like lego's NXT)
The interface has a small(ish) STM32 microcontroller that controls LEDs, servos, analog motors, IR and touch sensors.
It can accommodate any 4 of the above simultaneously at any of it's 4 RJ25 ports.

Now, I want to be able to identify which peripheral component is connected at which (of the 4 RJ25) ports automatically
(in order to program the device accordingly) without manually assigning each port according to what I've connected.
I'm not sure how I should proceed, my initial thought was to sense the resistance of a pin (by the use of a bridge and the
ADC of the microcontroller) in order to identify the peripheral but I don't know if this will work.

Any ideas? Has anyone came across something similar?

Thanks!

 

[spudboy488]

That's one way. Have a fixed resistor on the main board and use the peripheral resistor as a voltage divider and measure with an ADC. Make sure to leave a big enough gap between values to allow for tolerance stack up.

Another way, especially if you think you're going to have a fair number of different sensors, is to use a I2C port expander (such as a MCP23008) on each sensor board. It is an 8-bit I/O chip. Simply strap the 8 bits to a different address for each sensor and use the 2 I2C lines to read what is connected. This will allow up to 256 different sensors.