1. Example 6 Hex Keypad
Lecture L3.2

2. miniDragon+
2 pushbutton switches
Serial cable
A/D Pot
I/O headers
Run/Load switch
Reset button
7-segment display
Power plug
Keypad header

4. 4 x 4 Hex Keypad

5. 4 x 4 Hex Keypad

6. int key_scan(void) int key_scan(void){ const char keycodes[] = {
0xD7,0xEE,0xDE,0xBE,
0xED,0xDD,0xBD,0xEB,
0xDB,0xBB,0x7E,0x7D,
0x7B,0x77,0xE7,0xB7 };
int i,j, key;
char readback;
int found;
i = 0;
key = 16; // return 16 if no key pressed
found = 0;
while((i < 16) && (found == 0)){
PORTA = keycodes[i]; // write keycode to PORTA
for(j = 0; j<10; j++){
} // wait a bit
readback = PORTA;
if(readback == keycodes[i]){ // read back PORTA, if same
key = i; // get key number
found = 1; // and exit loop }
else
i++; // else check next key
return key; // return key
int key_scan(void)

7. void wait_for_keyup(void)
int get_key(void)
int get_key(void){
int key;
do {
key = key_scan(); }
while(key == 16);
return key;
void wait_for_keyup(void){
while(key_scan() != 16){
void wait_for_keyup(void)

8. Example 6a // Example 6a: 4 x 4 keypad in C
#include <hidef.h> /* common defines and macros */
#include <mc9s12dp256.h> /* derivative information */
#include "main_asm.h" /* interface to the assembly module */
#pragma LINK_INFO DERIVATIVE "mc9s12dp256b"
int key_scan(void);
int get_key(void);
void wait_for_keyup(void);
void main(void) {
int c;
PLL_init(); // set system clock frequency to 24 MHz
seg7_enable(); // enable 7-segment display
DDRA = 0x0F; // Port A: A7:A4 inputs, A3:A0 outputs
while(1){
c = get_key();
seg7dec(c);
wait_for_keyup(); }

9. Example 6

10. Example 6b // Example 6b: 4 x 4 keypad using C function calls
#include <hidef.h> /* common defines and macros */
#include <mc9s12dp256.h> /* derivative information */
#include "main_asm.h" /* interface to the assembly module */
#pragma LINK_INFO DERIVATIVE "mc9s12dp256b"
void main(void) {
char c;
PLL_init(); // set system clock frequency to 24 MHz
seg7_enable(); // enable 7-segment display
keypad_enable();
while(1){
c = getkey();
seg7dec(c);
wait_keyup(); }