MikroElektronika books

4.18 Example 16

 

Use a 4x4 keypad

A keypad is just a set of push-buttons connected in such a way to form 'rows' and 'columns', thus reducing a number of I/O pins necessary for their connection. A keypad with 16 push-buttons arranged in 4 rows and 4 columns is used in this example. The Keypad 4x4 library contains all the functions necessary for reading this keypad as well as for initializing the port it is connected to. In order to demonstrate the operation of the keypad 4x4, the message will be shown on an LCD display.
pic-microcontrollers-programming-in-basic-chapter-04-image-52
'Header******************************************************

program example_16 ' Program name
dim kp, curX, curY as byte
dim keypadPORT as byte at PORTD ' This variable must be defined in all projects using Keypad Lib.
 ' It define the port used for keypad connection

dim LCD_RS as sbit at RB4_bit ' Lcd module connections
LCD_EN as sbit at RB5_bit
LCD_D4 as sbit at RB0_bit
LCD_D5 as sbit at RB1_bit
LCD_D6 as sbit at RB2_bit
LCD_D7 as sbit at RB3_bit
LCD_RS_Direction as sbit at TRISB4_bit
LCD_EN_Direction as sbit at TRISB5_bit
LCD_D4_Direction as sbit at TRISB0_bit
LCD_D5_Direction as sbit at TRISB1_bit
LCD_D6_Direction as sbit at TRISB2_bit
LCD_D7_Direction as sbit at TRISB3_bit ' End Lcd module connections

main: ' Start of program
curX=1 ' For keeping a record of the 2x16 LCD cursor position
curY=1
ANSEL = 0 ' Configure analog pins as digital I/O
ANSELH = 0
TRISB = 0
PORTB = 0xFF
Keypad_Init() ' Initialize keypad on PORTC
Lcd_Init() ' Initialize LCD on PORTB,
Lcd_Cmd(_LCD_CLEAR) ' Clear display

while true ' Wait for some key to be pressed and released
 kp = 0
 while kp = 0
 kp = Keypad_Key_Click()
 Delay_ms(10)
 wend

 select case kp ' Prepare value for output
 case 1 kp = "1"
 case 2 kp = "2"
 case 3 kp = "3"
 case 4 kp = "A"
 case 5 kp = "4"
 case 6 kp = "5"
 case 7 kp = "6"
 case 8 kp = "B"
 case 9 kp = "7"
 case 10 kp = "8"
 case 11 kp = "9"
 case 12 kp = "C"
 case 13 kp = "*"
 case 14 kp = "0"
 case 15 kp = "#"
 case 16 kp = "D"
 end select

 if (curY > 16) then ' Change cursor position
 if (curX = 1) then
 Lcd_Cmd(_LCD_SECOND_ROW)
 curX = 2
 curY = 1
 else
 Lcd_Cmd(_LCD_FIRST_ROW)
 curX = 1
 curY = 1
 end if
 end if
 
 Lcd_Chr_CP(kp) ' Display on LCD
 Inc(curY)
wend

end. ' End of program
In order to make this example work properly, it is necessary to check the following libraries in the Library Manager prior to compiling:
  • Keypad4x4
  • LCD