I am developing a data logger for use in high schools like ( http://www.pasco.com ). The main difference is that mine is primary supposed to be used with an iPad. I have a connection between a micro controller and an iPad up and running, but I have a question regarding the communication between sensors and the 'hub' which is the part that makes it possible to connect up to 3 sensors to the iPad.
On the prototype level my hub consists of an Atmega328 (arduino) and the sensors are just connected directly to the A/D converter pins.
But because this system is supposed to support a variety of sensors this solution is not generic enough (i.e.. if a distance sensors should be connected, it would not work on the anlog pin, because it would be the difference between 2 timestamps). So I am thinking of adding a micro controller in every sensor and let that microcontroller communicate with the micro controller of the hub, which then will transmit the data to the iPad.
Which protocols should be used to communicate between these micro controllers? And is at all the way to go?
- The length of the wire would be maximum 2m.
- The maximum amount of wires is 4 and it should include +5 and GND to the sensor.
- The readings should in some cases be fast 20hz or preferably even more.
- It should be possible to send some sort of identification along to the hub, so the hub knows which kind of sensors is attached.
It is possible to see a video of the prototype here.