GPIODM-KPLCD Microchip Technology, GPIODM-KPLCD Datasheet - Page 14

• Manufacturer Part Number: GPIODM-KPLCD
• Description: BOARD DEMO LCD GPIO EXP KEYPAD
• Manufacturer: Microchip Technology

Specifications of GPIODM-KPLCD

• Main Purpose: Interface, Front Panel Controller, LCD
• Embedded: Yes, MCU, 8-Bit
• Utilized Ic / Part: MCP23008, MCP23S08, MCP23017, MCP23S17, PIC18F4550, MCP1702
• Primary Attributes: (2) 8-Bit and (2) 16-Bit GPIO Expanders, 4x4 Keypad, 2x16 LCD
• Secondary Attributes: Headers for the MCP23x08 and MCP23x17
• Silicon Manufacturer: Microchip
• Core Architecture: PIC
• Core Sub-architecture: PIC18
• Features: SPI And I2C Buses, Keypad And LCD Interface, ICSP Header
• Kit Contents: Board
• Silicon Core Number: PIC18F
• Silicon Family Name: PIC18F4xxx
• Rohs Compliant: Yes
• Lead Free Status / RoHS Status: Not applicable / Not applicable
• For Use With: MCP23S08/17, MCP23008/17
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant, Not applicable / Not applicable

GPIO Expander Keypad and LCD Demo Board User’s Guide
2.5
DS51636A-page 10
FIRMWARE DESCRIPTION
See
Main Function:
1. The firmware first configures the PIC MCU.
2. The MCP23X08 and MCP23X17 devices are configured. I
3. The LCD splash screen is shown.
4. Wait for an interrupt from the MCP23X08. An interrupt will occur when a button
5. After the interrupt occurs, the firmware calls the Scan_Buttons routine.
6. Then the Update_LCD routine.
Scan_Buttons Function:
1. Read INTCAP register. This register contains a snapshot of the port condition
2. Swap inputs and outputs so the rows can be read.
3. Read GPIO register and merge with variable containing INTCAP value.
4. The pressed key is determined by looking up the result in a lookup table.
Update_LCD Function:
1. The LCD is updated based on which button was pressed.
selected first by default. The SPI devices I/O are held in reset.
is pressed. Four (4) inputs are configured to interrupt on falling edge. These
inputs are for the “columns” of the keypad matrix.
when the interrupt occurred.
Figure 2-3
for the main firmware flow diagram.
© 2006 Microchip Technology Inc.
2
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