100 ns pulse measurement


I am relatively new to arm and would like to ask your opinion on what board would be good for my project. I have mostly done C coding.

I have project where pulse length and voltage level needs to be measured and based on that stepper motor is driven. 

Requirements are:

- ADC to measure minimum pulse length of 100 ns, 100 kHz pulse frequency and voltage level

- 2 ore more UART:s to communicate with PC and other devices

- I2C or comparable to send periodically information to other devices

I am trying to measure current pulse length and control stepper motor based on the pulse length. Voltage level needs to be measured to find short circuits and for fine tuning motor position. Pulse length varies based on motors position. I have done this previously by using RC-filter and software averaging based on measured voltage level. Motor has been controlled using Proportional control. But this doesn't give any true information about the actual process.