PIC16F883 over 12V input with resistors?

I am using a ADM00308 with a MTS2916A driver development board from MicroChip. There is a serial port RX & TX which can be programmed into an input. I'll use those inputs to drive the motor a specific direction. The signals I will be using is 4.5V for the motor going clockwise. By going counterclockwise the signal will be 18V. This is because the clockwise speed is setted to be slower than the reverse speed. I am planning to tap these signals and put it on my input. Since the operating voltage of the PIC16F833 processor is 2V to 5.5V , am I able to put 18V with a 10k resistor on the input of the processor? The current is about 0.150A.

Since for example 3.3V leds can be driven by a supply of 12V with a specific resistor on it, I am not sure if the same applies for input of microprocessors. Sorry for my potential silly question.

The board you are using has a three-terminal regulator that drops the input voltage to 5 volts. It is rated only to 16 volts and requires 7 volts to operate. The MTS2916A motor driver requires a minimum 4.5 volts on its logic input, which is supplied from this regulator. Since the regulator has a voltage drop associated with it, the board will not work with either 4.5 or 18V on the input.

You can remove jumper JP2 on the board and apply your 4.5 - 18 volts directly to the jumper pin connected to VLoad on the MTS2916A, and use a separate battery or supply (sharing the same ground) of 7-16 volts on the J1 input. A standard 9V battery would be fine here.

To use the RX pin as an input you could use a resistor divider to bring your 18 volts down to a logic level:

simulate this circuit – Schematic created using CircuitLab

• Thank you for your answer. The voltage for the reverse signal is going to be on the RX pin. However, it's around 18V. I've measured the pins and it looks like RX and TX pins are directly connected to the processor. The voltage is too high and I don't know if a resistor would prevent damage. I am trying to modify this board to work automatically without the buttons. – Capt. Frost May 21 '18 at 15:39
• Got it. I modified my answer to add a schematic. – John Birckhead May 21 '18 at 16:13
• Thank you so much! Marked yours as answer! Once again, thank you for your time and effort. I hope the processor won't burn up haha. – Capt. Frost May 21 '18 at 17:15