Step to realize the interfacing of switch and LED with KL25Z FRDM board.

Interfacing diagram of Switch and LED with FRDM KL25Z board

 switch taken from 4X4 matrix keypad

- Switch 1 from matrix keypad is taken as one of the switch and for that we need to connect the matrix   key pad to the FRDM KL25Z board with the port C pin 0-3 as for row and 4-7 as column.

- However we will use single key from 16 keys of the 4X4 matrix keypad, to demonstrate the switch and LED interface with the KL25Z board.

 Steps:

1) Enable clock to the ports C-keypad and D- blue LED connected.

2) to configure the switch we need to follow below mention steps.

- Row connected as an output and column connected as an input configure all through respective pin's PDDR registers.

- Columns are connected as input and connected through the internal pull up registers. 

- to configure input pullup registers enable bits 0 (PS) and 1 (PE) of PCR along with MUX field- bits 10-8 as GPIO ( 001). For details you can refer the diagram given below.

- 0x103 is the number that we need to load in to PCR of particular pin to configure it with the internal pull up register.

- Rows are connected as output and we need to configure it as GPIO through PCR register by loading 001 into bits 10-8 of MUX field. 

3) Configure blue LED of the board as output through PDDR register.

4) Apply logic to  detect the switch.

5) if switch is detected LED should glow and not than LED turned off.