Power MOSFET transistors are voltage controlled switches. They begin to turn on at their rated “gate threshold voltage” or Vgs(th). Most of the datasheet ratings are given for a fully saturated condition, typically 10 volts. There is also a maximum allowable gate voltage, Vgs, that is typically 20 volts. Any voltage greater than that will pierce the thin metal oxide layer that insulates the gate from the rest of the silicon die, destroying the device. This is why uninstalled MOSFETS can be so sensitive to electrostatic discharge (ESD) damage.
While many of the PIC microcontroller models have at least one hardware PWM output channel that could be used to control an h-bridge, we’ll take a quick look at several models that are particularly well suited for servo and stepper motor control applications.
If you’re designing a device that spends most or all of it’s time connected to a PC through a USB port, it is probably best to design USB connectivity right into the device. However, if the device only needs to be connected occasionally to change settings or download data logs, it might be convenient to use a separate adapter that translates USB protocol to TTL level asynchronus serial signals that talk to the microcontroller’s UART. Also, if you’re a hobbyist, you may not want to spend a lot of time understanding the details of USB interfacing hardware and protocols. I recently stumbled upon an adapter that makes this easy.