Front Panel For 8 Bit Computers
Contents
Front Panel for 8-Bit Microprocessors
Top row controls
Typical controls.
Features
It has these features. They may not fit your generic design. Especially since this card has to have an I2C interface.
- 32 Pushbutton Switches
- 32 LEDs
- I2C interface (Two Wire interface - plus power and ground)
- Jumper selectable base address
- Occupies I2C addresses either 0x20-0x23 or 0x24-0x27
- Jumper Selectable I2C terminators
- I2C daisy-chain connector
- Interrupt line
- Can be configured to interrupt on button presses
- MCP23017 need to be set to Open-Drain output - card has pull-up to Vcc
- Interrupt line
- 4 MCP23017 16-bit I2C Port Expanders
- These are fine pitch surface mount parts
- MCP23017 Datasheet - Rev D
- MCP23017... LOST TWO INPUTS
- MCP23017 now a 14/16-bit expander, with two of the pins (GPA7 and GPB7) losing their input capabilities
- The chips look the same, are called the same, and act mostly the same — if you don’t download the latest version of the datasheet (Revision D), you’d never know that there’s been a change
- 3.3V or 5V operation
- Compatible form factor with RETRO-EP4CE15 and other cards
- 95x95mm
- 6-32 mounting holes
Connector
J2 - I2C Connector
- Two row header on bottom of card
- 5 pin in
- 4 pin out (daisy-chain)
- GND
- VCC
- SDA
- SCL
- INT*
And
- GND
- VCC
- SDA
- SCL
Schematic
Drivers
VHDL Driver
- VHDL code to control Front Panel autonomously
- Great for FPGA Retro-computers
- Converts pushbuttons into raw, debounced, and toggled outputs
- Uses IOP16 small CPU core
- Example: 6800 running MIKBUG using the Front Panel - Run/Halt the CPU, Read SRAM, ROM, etc, Write to SRAM
VHDL Entity
-- -------------------------------------------------------------------------------------------------------
-- Front Panel starts here
fp01 : work.FrontPanel01
port map
(
-- Clock and reset
i_CLOCK_50 => i_CLOCK_50, -- Clock (50 MHz)
i_n_reset => w_resetClean_n, -- Reset
-- 32 outs, 32 ins
i_FPLEDs => w_LEDsOut, -- Out to LEDs (32)
o_PBRaw => w_PBsRaw, -- Raw version of the Pushbuttons (32)
o_PBLatched => w_PBLatched, -- Latched version of the Pushbuttons (32)
o_PBToggled => w_PBsToggled, -- Toggle version of the Pushbuttons (32)
-- I2C interface
io_I2C_SCL => io_I2C_SCL, -- I2C clock to Front Panel card
io_I2C_SDA => io_I2C_SDA, -- I2C data to/from Front Panel card
i_I2C_INTn => i_I2C_INTn -- Interrupt input - active low
);
-- Front Panel ends here
-- -------------------------------------------------------------------------------------------------------
Arduino Driver
- I2C parts are standard MCP23017 drivers which are supported in Arduino and most microprocessors
