User manual

Installation and Operation
© 2006 Microchip Technology Inc. DS51636A-page 11
FIGURE 2-3: MAIN FIRMWARE FLOW
Start
Init_MCU
Init_MCP
GPIO INT Flag
Set?
YES
NO
Splash
Scan_Buttons
Update_LCD
The MCP23X08 is
configured to interrupt on
falling edge for the
columns (4 inputs)
After the interrupt, the column
location of the button is known
and is contained in INTCAP.
Need to read GPIO to get the
Row location.
Buttons:
0-9, #, * : Copied to the LCD
M: Toggle mode (SPI and I
2
C™)
B: Backspace
R: Carriage Return
S: Space