What is the motor's voltage and CURRENT rating?
There is a reverse polarity diode between the barrel jack and VIN pin, it will drop about 0.7 volts so, with 9V in, the voltage at VIN will be about 8.3. Also the diode's CURRENT rating is 1 Amp.
Aah, now I got you. The project I am creating requires a pluggable power supply. If it was not the case - of course there would be no doubt to connect to Vin inside the enclosement.
Good to know. 8V should be enough for the driver and for my low power NEMA 11, the current is also fine. But according to the above diagram - diode is after connection to VIn, so it won't be affected. Or the diagram is not real?
I see you are determined to use Vin as a output so I won't bother you anymore.
I won't tell you to do something that is contrary to the documentation without actually verifying that it is safe.
However I do not have an R4 for testing.