I connected the Monster Motor Shield (based on the VNH2SP30) to the Arduino Uno and successfully drive the engine, but I can not measure the value from the CS pin on this board (the voltage at this pin is proportional to the current flowing through the motor). I measured the voltage value of this pin using a multimeter and it turned out that 1 ampere of load is equivalent 40 mV, 2A - 80 mV, etc. But Arduino always shows a voltage of 0 V. I changed the AnalogReference to the Internal (the base value is 1.1V), but the result did not change (although at 40 mV the analogread should be about 37). With Arduino all okay, I checked with the help of voltage divider. The scheme on shilde is this: I suggested that the problem in the filter and replaced the 10K resistor with a 3.2K resistor, but that did not help. What is the problem with Arduino's strange behavior?
I've seen that people in other forums have faced the same problem, so I'll leave it here:
I found a solution to the problem (in my case). It was necessary to connect the ground of Arduino with the earth of the battery (from which the motor worked). Of course grounds was connected through Monster Motor Shieled, but apparently it's not so simple with it. The extra wire on the minus battery solved the problem.
By the way, the capacity on the image is incorrectly signed. Its real capacity is 33 nF.