I was working on the electronics for the TAS (Teutanic Automation System). I have tested most individual signal types on their own and now have mounted all the different board types I am using on a perspex plate to make a bit more solid test environment. I have too many individual pieces to just make it work free air on the desk. Not that I mount all the devices I am using, far from it, but enough of each type to test all the variations of the required control functions. Since we talk automotive electrics/electronics we deal mainly with 12V, which is not the voltage the microcomputers like. Their signal input is 5V or 3.3V and a signal conversion is required from 12V to the required input level. This can be done in various ways and I have made my own little boards for signal adaptation as well as using off the shelf boards as an alternative. I have not yet finally decided which board is used for what actual signal, I am still at the level of putting everything together in a lab environment and then decide which component goes where and is connected to which signal. Nevertheless once this test is over the central software and the firmware for the micros is finished and working and it only needs a few more signal definition entries to expand to the final level.
I use Digital In/Out 5V to 12V, Analogue In/Out 5V to 12V and 3.3V to 5V TTL and 3.3V to 12V, and also PWM out 3,3V to 12V and 5V to 12V. Ethernet and CAN Bus are used for communication between the nodes and I2C and one wire bus is used to connect the individual sensors.