1. 4-Integrating Peripherals in Embedded Systems (cont.)

2. Using push buttons and switches
Push buttons SW2 to SW5 on the Dragon Board are connected to bits 3 to 0 of PortH
When button is pushed, a corresponding bit of Port H is reset. What activity level?
Can be enabled/disabled:
SW_enable();
Can be checked with C function calls:
SW1_dip(); //returns 8-bit reading of SW1
SW2_down(); // true if SW2 is down
SW2_up(); //true if SW2 is up.
Use
while ((PTH & 0x01)==0) //to check if the SW5 is being pressed {
//…SW5 still pressed }
//SW5 released

3. Using switches
There are also 8 DIP switches (sliders) on the Dragon board.
The rightmost 4 switches share the same bits of portH with push buttons.
These switches are intended for use as level-sensitive data inputs to a circuit.
When a switch is in the ON position (away from LCD) it provides a 0 bit on corresponding PORT H bit.
What activity level?
Use:
DDRH=0x00; //Port H inputs
leds_on(~PTH);

4. Using Keypad keypad_enable() getkey() wait_keyup() keyscan()
The Dragon board has a 4x4 keypad, connected to Port A.
Scanning is used to minimize interface bits. See page 29.
Use C function call key_scan(). See listing 6.1
Use C function call get_key(). See listing 6.3
To avoid bouncing:
keypad_enable()
getkey()
wait_keyup()
keyscan()

5. Using LEDs The Dragon board provides 8 red LEDs.
You can use C function calls to set/reset LEDs
led_on(int b); //Sets bit b of PORTB High, or on
led_off(int b); //Sets bit b of PORTB Low, or off
leds_on(int h); //Sets bits of all 8 leds according to hexadecimal value h

6. Seven Segment Display
The Dragon Board has four 7-segment displays. These displays are arranged with the intent of displaying numbers of medium sizes.
Must be enabled/disabled since using same port B of LEDs:
seg7_enable();
seg7_disable();
Applying a high logic level to a segment causes it to light up, and applying a low logic level turns it off.
seg7_on(int s, int b); //turns on segment s on 7SEG digit b
What will be the hexadecimal digit coding (assume 0 segment is least significant)? [9 coded as 0x6F]
Use seg7dec(int i, int b); //display hexadecimal value of i on 7SEG digit b

7. LCD controller
Dragon board has Sanyo DM1623 display of 2x16 characters.
See control signals in pg. 33 and table 7.1 in pg 34 E
R/W RS
DB7–DB0
LCD controller
communications bus
microcontroller 8

8. Using LCD See figure 4.7(d), pp 96 Void WriteChar (char c) { RS=0
/*indicate control being sent*/
DATA_BUS=0x01;//Clear Display
/*toggle LCD Enable, with delay*/
EnableLCD (45);
//…other controls
/*indicate data being sent */
RS=1;
/*send data to LCD */
DATA_BUS=c; }

9. Using LCD For Dragon12 we may use: char * msg; msg=“Dragon12-Plus”;
lcd_init(); //set configurations
set_lcd_addr(0x01);//for first line
type_lcd(msg);
set_lcd_addr(0x45); //for second line