Greeting...I am trying to Connect two PIC microcontrollers

[HenrikOlsson]

Hi,
What do you mean by all pins are being used?
A 4x3 matrix would require 7 pins and I see 8 free pins (RC2-7, RA4-5, RB5) on the '4550 in your schematic...

If you put a slave PIC on the keypad you could program it to SEROUT/HSEROUT a byte each time a key is pressed and connect it to the USART of the 4550 (RC7 is the RX input for the USART and is currently not used in your schematic.)

/Henrik.

[Freestyle]

Hi,
Thank you for your response and I am glad I found your answer. You are right there is more pins that the 3x4 can use. If you will, please guide me with the wiring connection. How would you connect the 3x4 keypad to the PIC18f4550? What pins from the keypad to what pins from the PIC?

Thank you for your time.

[HenrikOlsson]

Hi,
For a basic 4x3 matrix you need 4 output and 3 inputs OR 3 outputs and 4 inputs - up to you really. The outputs drives the columns (or rows) and the inputs reads the rows (or columns).
Pull up the inputs, drive one of the outputs low, read the inputs. If any of the inputs reads low you have a button pressed. Drive the next input low, read the inputs and so on.

If you search the forum I'm sure you'll find examples.

/Henrik.