Generally, that is done with a resistor, called a pull-up resistor, connecting the input of the controller to the power feeding the controller. Some controllers have internal pull-up resistors when an I/O pin is configured as an input.I am using two push on button as a limit switch, when i press the push button, it will send a signal to the controller, but the signal will cut off when unpressed.. is there any method to keep the signal to high-state when the push button is unpressed?