Nothing really fancy, the tester control the coil of the injector with different patterns. There's a few unit on the chinese market but they look pretty crap with their plastic case. This unit will be made for proper abusive workspace with a aluminium case.
Originally I wanted to make a 4 channel unit to be able to do test pattern for all the injector at once. But I realised there weren't resistors but coils that control the injector pin. On my Daewoo car, the impedance is 15.4R which means a lot of current ! (some units are even lower) which complexifies quite a bit the desing if I go this road.
The microcontroller is a STM32F0 that I have in stock in its SOP20 package. I added CMOS buffer to be able to use different kind of N-Channel mosfet to control the coil. Everything will be done with the PWM mode on the microcontroller that has an interesting "repetition" feature which is exactly what I want.
At the moment I still need to find documentation on the duration of the pulses depending on the condition (idle car, fast engine rev, ect...).