Explanation:
This program demonstrates how to control and display using a LCD the code for the keypad.
This program can be adapted. This program uses the hardware I2C module within the microcontroller. If your microcontroller does not have a hardware I2C module then please use the software I2C GCBASIC library for most microcontrollers.
This program also has an interrupt driven I2C handler to manage the I2C from the Start event.
Demonstration program:
'Code for the keypad and LCD Microchip PIC microcontroller on the Microlab board v2
'microcontroller is responsible for:
' - Reading keypad
' - Displaying data on LCD
' - communication with main Microchip PIC microcontroller via I2C
' - providing 5 keypad lines to main Microchip PIC microcontroller (for compatibility)
' - receiving remote control signals for button and keypad
'This code has support for two keypad layouts. This is one possible layout:
'0123
'4567
'89AB
'CDEF
'And this is the other possible layout:
'123A
'456E
'789D
'A0BC
'Select the keypad layout by uncommenting one of these lines:
'#define KEYPAD_KEYMAP KeypadMap0123
#define KEYPAD_KEYMAP KeypadMap123F
'Chip and config
#chip 16F882, 8
'Ports connected to keypad
'Column ports need pullups, hence columns are on PORTB for built in weak pullups
#define KEYPAD_COL_1 PORTB.4
#define KEYPAD_COL_2 PORTB.5
#define KEYPAD_COL_3 PORTB.6
#define KEYPAD_COL_4 PORTB.7
#define KEYPAD_ROW_1 PORTA.4
#define KEYPAD_ROW_2 PORTA.3
#define KEYPAD_ROW_3 PORTA.2
#define KEYPAD_ROW_4 PORTA.1
'Ports connected to LCD
#define LCD_IO 4
#define LCD_WIDTH 20 ;specified lcd width for clarity only. 20 is the default width
#define LCD_RW PORTA.7
#define LCD_RS PORTA.6
#define LCD_Enable PORTA.5
#define LCD_DB4 PORTA.4
#define LCD_DB5 PORTA.3
#define LCD_DB6 PORTA.2
#define LCD_DB7 PORTA.1
#define BACKLIGHT PORTA.0
'Button port (for remote control)
#define BUTTON PORTB.0
'Keypad ports connected to main Microchip PIC microcontroller
'These are disabled when KeyoutDisabled = true
#define KEYOUT_A PORTC.5
#define KEYOUT_B PORTC.2
#define KEYOUT_C PORTC.1
#define KEYOUT_D PORTC.0
#define KEYOUT_DA PORTB.1
'I2C ports
#define I2C_DATA PORTC.4
#define I2C_CLOCK PORTC.3
'RS232/USART settings
'To do if/when remote support needed
'Initialise
Dir KEYOUT_A Out
Dir KEYOUT_B Out
Dir KEYOUT_C Out
Dir KEYOUT_D Out
Dir KEYOUT_DA Out
Dir BACKLIGHT Out
Dir BUTTON In 'Is an output, turn off by switching pin to Hi-Z
'Initialise I2C Slave
'I2C pins need to be input for SSP module
Dir I2C_DATA In
Dir I2C_CLOCK In
HI2CMode Slave
HI2CSetAddress 128
'Buffer for incoming I2C messages
'Each message takes 4 bytes
Dim I2CBuffer(10)
BufferSize = 0
OldBufferSize = 0
'Set up interrupt to process I2C
On Interrupt SSP1Ready Call I2CHandler
'Enable weak pullups on B4-7 (keypad col pins)
NOT_RBPU = 0
WPUB = b'11110000'
'Key buffers
'255 indicates no key, other value gives currently pressed key
RemoteKey = 255
OutKey = 255
KeyoutDisabled = False 'False if KEYOUT lines used to send key
'Main loop
Do
'Read keypad, send value
CheckPressedKeys
SendKeys
'Check for I2C messages
ProcessI2C
Loop
'This keymap table is for this arrangement:
'0123
'4567
'89AB
'CDEF
Table KeypadMap0123
3
7
11
15
2
6
10
14
1
5
9
13
0
4
8
12
End Table
'This keymap table is for this arrangement:
'123F
'456E
'789D
'A0BC
Table KeypadMap123F
15
14
13
12
3
6
9
11
2
5
8
0
1
4
7
10
End Table
Sub CheckPressedKeys
'Subroutine to:
' - Read keypad
' - Check remote keypress
' - Decide which key to output
'Read keypad
If RemoteKey <> 255 Then
OutKey = RemoteKey
Else
EnableKeypad
OutKey = KeypadData
End If
End Sub
Sub EnableKeypad
'Disable LCD so that keypad can be activated
Set LCD_RW Off 'Write mode, don't let LCD write
'Re-init keypad
InitKeypad
End Sub
Sub I2CHandler
'Handle I2C interrupt
'SSPIF doesn't trigger for stop condition, only start!
'If buffer full flag set, read
Do While HI2CHasData
HI2CReceive DataIn
'Sending code
If BufferSize = 0 Then
LastI2CWasRead = False
'Detect read address
If DataIn = 129 Then
LastI2CWasRead = True
HI2CSend OutKey
KeyoutDisabled = True
Dir KEYOUT_A In
Dir KEYOUT_B In
Dir KEYOUT_C In
Dir KEYOUT_D In
Dir KEYOUT_DA In
Exit Sub
End If
End If
If BufferSize < 10 Then I2CBuffer(BufferSize) = DataIn
BufferSize += 1
Loop
End Sub
Sub SendKeys
'Don't run if not using KEYOUT lines
If KeyoutDisabled Then Exit Sub
'Send pressed keys
If OutKey <> 255 Then
'If there is a key pressed, set output lines
If OutKey.0 Then
KEYOUT_A = 1
Else
KEYOUT_A = 0
End If
If OutKey.1 Then
KEYOUT_B = 1
Else
KEYOUT_B = 0
End If
If OutKey.2 Then
KEYOUT_C = 1
Else
KEYOUT_C = 0
End If
If OutKey.3 Then
KEYOUT_D = 1
Else
KEYOUT_D = 0
End If
KEYOUT_DA = 1
Else
'If no key pressed, clear data available line to main Microchip PIC microcontroller
KEYOUT_DA = 0
End If
End Sub
Sub ProcessI2C
If HI2CStopped Then
IntOff
If LastI2CWasRead Then BufferSize = 0
If BufferSize <> 0 Then
OldBufferSize = BufferSize
BufferSize = 0
End If
IntOn
End If
If OldBufferSize <> 0 Then
CmdControl = I2CBuffer(1)
'Set backlight
If CmdControl.6 = On Then
Set BACKLIGHT On
Else
Set BACKLIGHT Off
End If
'Set R/S bit
LCD_RS = CmdControl.4
'Send bytes to LCD
LCDDataBytes = CmdControl And 0x0F
If LCDDataBytes > 0 Then
For CurrSendByte = 1 To LCDDataBytes
LCDWriteByte I2CBuffer(LCDDataBytes + 1)
Next
End If
'LCDWriteByte I2CBuffer(2)
OldBufferSize = 0
End If
End Sub