Download ECE-395 Microprocessor Laboratory

There is an LED on the FRDM-KL25Z is a tri-color red/green/blue device.
The common anode is tied to VDD. The three cathodes are tied through
resistors to GPIO’s as listed in Table 1. Because the LED is wired with the
common anode to VDD, the GPIO’s must be driven low to run on the LED
color and driven high to turn off the LED.
Table 1- KL25Z LED GPIO Assignments
LED Color
RED
GREEN
BLUE
GPIO
PTB18
PTB19
PTD1
Required Equipment and Parts

Solderless breadboard

Pushbutton

Jumper wires
Procedure
The aim of this lab is to wire a pushbutton to a GPIO on the FRDM-KL25Z,
then to write software to change the color of the on-board LED when the
button is pushed. The LED colors for pressed vs not pressed may be chosen
at the developers’ discretion.
1. Select the GPIO to be used for the pushbutton. Avoid the GPIO’s
assigned to the LED. On the solderless breadboard, wire the
pushbutton in a pull-up resistor configuration with one side of the
switch to the GPIO and the other to ground.
2. Write code to initialize the registers to enable the GPIO’s for the LED
outputs and switch inputs as follows:
SIM_SCGC5 <<< Enable the clocks for the IO ports, to keep things
simple all the clock can be enabled
PORTB_PCR18, PORTB_PCR19 and PORTD_PCR1 <<< Set to be
outputs
PORTx_PCRn <<< Set to be input with pull-up for the GPIO selected
for the pushbutton input
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