Front Panel for 8 Bit Computers V2

Front Panel for 8-Bit Microprocessors v2

See here for Ver 1 - SMT version

Features

This is a through-hole version of Front Panel for 8_Bit Computers.

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
• 4 of MCP23017 16-bit I2C Port Expanders
  • These are fine pitch surface mount parts
• 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)

1. GND
2. VCC
3. SDA
4. SCL
5. INT*

And

1. GND
2. VCC
3. SDA
4. SCL

Schematic

• Front Panel Schematic Rev 1

Legends

• D0-D7 - Data bus
• A0-A15 - Address bus
• Controls

Top row controls

Board has typical control silkscreen markings. It is all through hole so that it is much easier to assemble.

• RUN - Run/Halt pushbutton, RUN LED on for CPU running
• RESET - Reset the CPU
• STEP - Single Step the CPU
• Undefined
• CLEAR - Clear address bus (if SETADR is ON) or data bus lines (if SETDAT is ON)
• INCADR - Increment the address
  • If SETDAT is on write data
• SETDAT - Set the data value
• SETADR - Set the address

Drivers

VHDL Driver

• VHDL code to control Front Panel autonomously - Great for FPGA Retro-computers
  • Converts pushbuttons into raw, debounced, and toggled outputs
  • Example: 6800 running MIKBUG using the Front Panel - Run/Halt the CPU, Read SRAM, ROM, etc, Write to SRAM
    • IOP Code - Controls the Front Panel

VHDL Entity

-- -------------------------------------------------------------------------------------------------------
	-- Front Panel starts here
	-- Pass IOP16 code size and stack size down to the Front Panel
	fp01 : work.FrontPanel01
		generic	map ( 
			INST_ROM_SIZE_IN	=> 512,						-- 512W code size
			STACK_DEPTH_IN		=> 4							-- 16 deep stack size
		)
		port map
		(
			-- Clock and reset
			i_CLOCK_50			=> i_CLOCK_50,				-- Clock (50 MHz)
			i_n_reset			=> i_n_reset,				-- Reset (from FGPGA KEY)
			-- 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
  • LandBoards_MCP23017 library
  • Importing an Arduino ZIP library

Micro-Python

• Micro-Python driver for MCP23017

PSoC Control

• Z80 example

C Code

• PSoC driver GitHub Repo
  • FrontPanel.c
  • FrontPanel.h
  • MCP23017.c
  • MCP23017.h

Assembly Sheet

Front Panel V2 Assembly Sheet Rev 1