You need to make sure that the power supply for the micro is the same as the one at the top of the H. Otherwise you may not be able to turn off the top transistors. If the power is 5 volts the base current in the transistor will be about 4.3 ma. This is enough for the transistors to switch about 43 ma. So if your little motor measures about 100 ohms or more you can drive it. In reality you could probably drive one down to 50 ohms but things may get a little warm if it is stalled.