This is how to build a very easy and cheap Sim Racing USB display with an Arduino UNO and a 3,5" TFT Display.
It has an API for Assetto Corsa that takes the data from the Shared Memory of the game programed in C# in Visual Studio, then send the data to the Arduino throught USB, the Arduino parses the data and show it.
I am developing the API for Project Cars, and then I will do it for rFactor, so subscribe to my YouTube Channel to be updated.
Step 1: Materials
You only need an Arduino UNO(I tested my MEGA and doesn't work properly the parsing) and a MCUFriend TFT 3,5" Shield for UNO
It rounds moreless 35-40€ all.
Step 2: Data and GUI
The GUI is so simple, it has a black background where will display 10 different values, RPMs, Speed, Gear, Fuel, Boost, Air Temp, Asphalt Temp, Gas, Brake and Engine Brake.
Some values like Boost, sometimes stay at 0(NULL); that's because teh car you are driving, hasn't boost so it keeps the value at 0.
Step 3: Building
I have attached the Program that you must run(is the API), then select the COM port of your Arduino
** IMPORTANT: You have to write COMX, for example my Arduino is in COM9 as displayed in the picture.
And upload the .hex file attached to your Arduino
You can download the files here: MEGA