6502-COB

An AC6502 retro-style 8-bit computer based on the 65C02 microprocessor.

📖 Guide:AC6502 Documentation — the user's and programmer's guide for the whole family. See COB's page in the family appendix.

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Table of Contents

• Overview
• Architecture
• Systems
• Software
• Hardware
  • Backplanes
  • Cards
  • Helpers
• Firmware
  • KEH Controller
  • PS2 Keyboard Controller
  • STP Controller
• CAD
• Production
• Schematics
• Libraries
• Bill of Materials
  • Backplane
  • Backplane Helper
  • Backplane Pro
  • Blinkenlights Card
  • Breadboard Helper
  • Clock Helper
  • CPU Card
  • CPU Card Pro
  • DB25 Helper
  • GPIO Breadboard Helper
  • GPIO Card
  • GPIO Helper
  • Joystick Helper
  • Keyboard Encoder Helper
  • Keyboard Helper
  • LCD Board
  • LCD Card
  • Mega Helper
  • Memory Card
  • Prototype Card
  • PS2 Helper
  • RAM Card
  • RTC Card
  • Serial Card
  • Serial Card Pro
  • Sound Card
  • Storage Card
  • Storage Card Pro
  • VERA Helper
  • VGA Card
  • VGA Card Pro
  • Video Card
  • Video Card Pro
• Purchase
• License

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Overview

The AC6502 ecosystem is a family of open-source, 65C02-based computers sharing a common architecture, memory map, and BIOS. Each computer in the family is purpose-built for a different use case but runs the same software and firmware.

The COB (Computer on a Backplane) is a full-featured modular desktop computer. It features a real 65C02 CPU, a backplane architecture with expandable card slots, up to 544KB RAM, composite or VGA video output, CompactFlash or SD storage, a real-time clock, and support for PS/2 keyboards, matrix keyboards, and Atari 2600-compatible joysticks.

Architecture

All AC6502 computers share:

• CPU: 65C02 (or accurate emulation)
• Memory: 32KB RAM + 32KB ROM, with optional banked RAM expansion
• Memory Map: Standardized across the ecosystem — zero page, stack, I/O space ($8000–$9FFF), system ROM, and interrupt vectors at $FFFA–$FFFF
• Bus: 16-bit address bus, 8-bit bidirectional data bus, standard 65C02 control signals (RW, PHI2, RESET, IRQ, NMI, RDY, SYNC)
• BIOS: A common BIOS provides the kernel, monitor, and BASIC interpreter across all systems

Systems

Project	Description
6502-ACE	All-in-one Computer Experience — A single board computer
6502-COB	Computer On a Backplane — Modular desktop computer with expandable card slots (YOU ARE HERE)
6502-DEV	Development Environment Vehicle — Emulation-based dev system
6502-KIM	Keypad Input Monitor - KIM-1 inspired minimal computer
6502-VCS	Video Computer System — Cartridge-based retro gaming console

Software

Project	Description
6502-BIOS	The shared BIOS (kernel, monitor, BASIC) for all AC6502 computers
6502-EMULATOR	Emulator for the whole family — desktop app, browser build, and a command line for scripted runs
6502-PRG	Template project for writing assembly language programs
6502-CRT	Template project for writing assembly language cartridges
6502-ASM	Assembly language example programs and demos
6502-BAS	BASIC program listings
6502-WOZMON	Wozmon as a standalone ROM
6502-NOP	An all-NOP ROM, for probing a board during bring-up
6502-DOCS	The documentation site — the guide, the printable reference cards, branding and label artwork
cffs	Builds CompactFlash disk images for the BIOS filesystem
bastok	Tokenizes BASIC listings into .prg images, and back
bin2woz	Converts a binary into a Wozmon serial upload

Hardware

This repository contains KiCad 7.0+ PCB designs for the backplanes, cards, and helpers that make up the COB system.

Backplanes

Hardware/Backplane/ — Passive backplane providing 5 card slots with full bus interconnect across all slots.

Hardware/Backplane Pro/ — Enhanced backplane with integrated clock generation, reset circuitry, and power distribution plus 5 card slots. Rev 1.1 moves to entirely through-hole components and adds an onboard power switch and DC barrel jack input.

Hardware/Backplane Helper/ — Adds additional card slots to expand the total backplane configuration up to 12 slots.

Cards

Hardware/CPU Card/ — Hosts the 65C02 CPU in a card form factor for backplane-based COB systems.

Hardware/CPU Card Pro/ — Hosts a 65816 16-bit CPU (backward-compatible with 65C02). (Untested)

Hardware/Memory Card/ — Provides 32KB SRAM and 32KB EEPROM with address decoding logic for COB systems using the CPU Card.

Hardware/RAM Card/ — 512KB banked RAM expansion organized as two 256KB banks with 256 × 1KB windows each.

Hardware/RTC Card/ — Real-time clock via Dallas DS1511Y with battery backup and 256 bytes of battery-backed SRAM.

Hardware/GPIO Card/ — General-purpose I/O via 65C22 VIA supporting keyboards, joysticks, timers, and custom devices.

Hardware/Serial Card/ — RS-232 serial communication via 65C51 ACIA and MAX232 level shifter.

Hardware/Serial Card Pro/ — Enhanced serial card with full modem control signals (DTR, DCD, DSR).

Hardware/VGA Card/ — VGA 640×480 video output via Raspberry Pi Pico running Pico9918 with TMS9918A-compatible graphics modes.

Hardware/VGA Card Pro/ — Fully programmable VGA output using Pi Pico with custom firmware. (Untested)

Hardware/Video Card/ — Composite video output via TMS9918A Video Display Processor with 16KB video RAM.

Hardware/Video Card Pro/ — Enhanced composite video card. (Untested)

Hardware/Sound Card/ — 3-voice SID audio output via ARMSID module with RCA line-level output.

Hardware/Storage Card/ — CompactFlash storage interface supporting up to 128GB via IDE-compatible protocol.

Hardware/Storage Card Pro/ — SD card (up to 32GB) and 16MB onboard SPI flash storage interface. (Untested, experimental — the stock BIOS has no driver for it; see STP Controller)

Hardware/LCD Card/ — 16×2 character LCD display via 65C22 VIA in 4-bit or 8-bit mode.

Hardware/Blinkenlights Card/ — Visual bus monitoring with LEDs showing address bus (16), data bus (8), and control signals (8) in real time.

Hardware/Prototype Card/ — Blank prototyping area with integrated breadboard and full bus access headers.

Helpers

Hardware/Keyboard Encoder Helper/ — ATmega1284p-based dual keyboard encoder supporting PS/2 keyboard and 8×8 matrix keyboard simultaneously via 65C22 VIA.

Hardware/PS2 Helper/ — ATmega328p-based PS/2 keyboard bridge that drives an MT8808 analog crosspoint switch to emulate a matrix keyboard. Its output is a raw 8×8 matrix and feeds the matrix inputs of a Keyboard Encoder Helper, which is what talks to the 65C22 VIA — not the VIA directly.

Hardware/Keyboard Helper/ — 64-key matrix keyboard with Atari 2600-compatible joystick support.

Hardware/GPIO Helper/ — 8 buttons and 8 LEDs for testing and debugging GPIO Card connections.

Hardware/GPIO Breadboard Helper/ — Breadboard interface adapter for the GPIO Card.

Hardware/Joystick Helper/ — Atari 2600-style dual joystick connector and interface board.

Hardware/Clock Helper/ — Manual clock control providing single-step, free-run, and halt modes for debugging real CPU systems.

Hardware/DB25 Helper/ — GPIO to DB25 connector adapter for external device interfacing.

Hardware/Breadboard Helper/ — Exposes the full AC6502 bus to a breadboard for prototyping and experimentation.

Hardware/Mega Helper/ — Arduino Mega 2560 interface adapter for the AC6502 bus.

Hardware/LCD Board/ — 320×240 TFT LCD display (ILI9341) interfaced via 65C22 VIA. (Untested)

Hardware/VERA Helper/ — VERA FPGA video module adapter for the AC6502 bus.

Firmware

This repository contains PlatformIO-based firmware for the COB system's microcontroller helpers.

KEH Controller

Firmware/KEH Controller/

Firmware for the ATmega1284p on the Keyboard Encoder Helper. Provides:

• Simultaneous PS/2 keyboard and 8×8 matrix keyboard scanning
• ASCII conversion with modifier key support (Shift, Ctrl)
• Buffered, debounced input handling
• Parallel I/O to the AC6502 bus via 65C22 VIA

See Firmware/KEH Controller/README.md for setup and usage instructions.

PS2 Keyboard Controller

Firmware/PS2 Keyboard Controller/

Firmware for the ATmega328p on the PS2 Helper. Provides:

• Interrupt-driven PS/2 keyboard scan code reading
• MT8808 analog crosspoint switch matrix control
• Make/break detection and extended scan code support
• Function key emulation via FN key combinations

The MT8808 closes row/column contacts in place of physical key switches, so this card connects to the matrix inputs of a Keyboard Encoder Helper, not to a 65C22 VIA. The encoder does the scanning and ASCII conversion; wired straight to a VIA the card produces nothing, as the BIOS has no matrix-scanning code.

See Firmware/PS2 Keyboard Controller/README.md for setup and usage instructions.

STP Controller

Firmware/STP Controller/

Firmware for the ATmega328p on the Storage Card Pro. Provides:

• Memory-mapped SPI controller for 6502 bus access
• Support for SD card, 16MB SPI flash, and external SPI devices
• Dual-speed SPI (4 MHz normal operation, 400 kHz initialization)
• PHI2-synchronized interface for reliable 6502 communication

⚠️Experimental. The Storage Card Pro is not part of the default I/O set the BIOS probes for, and no COB machine is built around it today. The BIOS storage slot expects eight True IDE CompactFlash registers at $8C00–$8C07; this card presents two SPI registers instead, so a stock BIOS reports NO DEVICE for every storage path. Using it needs a modified BIOS or software that drives the two registers directly.

See Firmware/STP Controller/README.md for setup and usage instructions.

CAD

CAD/

3D-printable enclosure parts and laser-cut top panels for the COB system.

Production

Production/

JLCPCB-ready Gerber files and BOM/CPL for PCB fabrication and assembly.

Schematics

Schematics/

PDF schematics for each board.

Libraries

Libraries/

Shared KiCad symbol and footprint libraries used across all AC6502 hardware projects.

Bill of Materials

Backplane

Reference	Qty	Value	Description	DigiKey	Mouser
J1–J5	5	6502 Card Connector	Card Edge 2×20	A31723-ND	571-5-5530843-4
J6, J7	2	6502 Bus	Bus Connector 2×20	732-5401-ND

Backplane Helper

Reference	Qty	Value	Description	DigiKey	Mouser
J1, J2	2	6502 Card Connector	Card Edge 2×20	A31723-ND	571-5-5530843-4
J3	1	6502 Bus	Bus Connector 2×20	732-5401-ND

Backplane Pro

Rev 1.1

Reference	Qty	Value	Description	Mouser
C1, C3	2	10uF	Polarized capacitor
C2	1	100nF	Unpolarized capacitor
D1	1	LED	Power LED 3mm
J1	1	5V DC	DC Barrel Jack	640-DCJ200-10-A-K1-K
J2–J4, J7, J8	5	6502 Card Connector	Card Edge 2×20	571-5-5530843-4
J5	1	CLOCK ENBL SW	Pin Header 1×2
J6	1	RESET SW	Pin Header 1×2
J9	1	6502 Bus	Bus Connector 2×20
JP1	1	Solder Jumper	Solder Jumper 2-pole
Q1	1	2N3904	NPN Transistor TO-92
R1	1	330	Resistor
R2	1	1M	Resistor
R3	1	47k	Resistor
R4	1	10k	Resistor
R5	1	1k	Resistor
SW1	1	POWER	SPDT Power Switch	612-400MSP1R6BLKM6QE
SW2	1	RESET	Tact Push Button 5mm
U1	1	LM555	Timer SOIC-8
X1	1	OCXO-14	Crystal Oscillator DIP-14

Rev 1.0

Reference	Qty	Value	Description	LCSC	DigiKey	Mouser
C1, C3–C14	13	100nF	Unpolarized capacitor	C49678
C2	1	10uF	Polarized capacitor	C7171
D1	1	1N5819	Schottky Diode SOD-323F	C191023
D2	1	LED	LED 0805	C2297
J1	1	PWR_SW	JST XH 1×2		455-2247-ND
J2	1	USB-C	USB 2.0 Type-C Receptacle	C2988369
J3	1	RESET_SW	JST XH 1×2		455-2247-ND
J4	1	CLOCK_ENBL_SW	JST XH 1×2		455-2247-ND
J5–J9	5	6502 Card Connector	Card Edge 2×20		A31723-ND	571-5-5530843-4
J10	1	6502 Bus	Bus Connector 2×20
Q1	1	SS8050	NPN Transistor SOT-23	C2150
R1	1	1M	Resistor	C17514
R2	1	47k	Resistor	C17713
R3	1	1k	Resistor	C17513
R4	1	10k	Resistor	C17414
R5, R6	2	5.1k	Resistor	C27834
R7	1	330	Resistor	C17630
SW1	1	Reset	Push Button	C318884
U1	1	LM555xM	Timer SOIC-8	C7593
X1	1	OCXO-14	Crystal Oscillator DIP-14

Blinkenlights Card

Reference	Qty	Value	Description	LCSC
C1–C4	4	100nF	Unpolarized capacitor	C49678
D1–D25	25	LED	LED 0805	C2297
D26, D27	2	LED	LED 0805	C2295
D28–D30	3	LED	LED 0805	C2296
D31, D32	2	LED	LED 0805	C2293
R1–R32	32	330	Resistor	C17630
U1, U2, U4	3	74HC573	8-bit Latch SOIC-20	C5608
U3	1	74HC04	Hex Inverter SOIC-14	C5590

Breadboard Helper

Reference	Qty	Value	Description	DigiKey
J1	1	6502 Bus	Bus Connector 2×20	732-5401-ND
J2, J3	2	Pin Header	Pin Header 1×20

Clock Helper

Reference	Qty	Value	Description
C1	1	100nF	Capacitor
D1, D2	2	LED	LED 3mm
J1	1	IO	Pin Header 1×5
R1–R5	5	1k	Resistor
R6–R8	3	330	Resistor
SW1, SW2	2	XKB5858-Z	DPDT Toggle Switch
SW3	1	XKB5858-W	DPDT Toggle Switch
U1	1	74HC74	Dual D Flip-flop DIP-14

CPU Card

Reference	Qty	Value	Description	LCSC
C1	1	100nF	Unpolarized capacitor	C49678
J2	1	Pin Header	Pin Header 1×2
J3	1	EXP	Pin Header 2×5
R1–R6	6	10k	Resistor	C2930231
U1	1	65C02	CPU DIP-40

Revision History

Rev 1.1

• Pull-up resistors changed from 1kΩ to 10kΩ.

Rev 1.0

• Initial release.

CPU Card Pro

Reference	Qty	Value	Description	LCSC
C1–C4	4	100nF	Unpolarized capacitor	C49678
J2	1	BANK ADDR	Pin Header 2×5
J3	1	EXP	Pin Header 2×4
R1–R6	6	1k	Resistor	C17513
U1	1	65C816	CPU DIP-40
U2	1	74HC00	Quad NAND SOIC-14	C5586
U3	1	74HC245	Octal Bus Transceiver TSSOP-20	C5626
U4	1	74HC573	8-bit Latch SOIC-20	C5608

DB25 Helper

Reference	Qty	Value	Description	DigiKey
J1	1	PORT A	GPIO Connector 2×6
J2	1	PORT B	GPIO Connector 2×6
J3	1	KEYBOARD	DB-25 Connector (Male)	609-1505-ND

GPIO Breadboard Helper

Reference	Qty	Value	Description
J1	1	PORT A	GPIO Connector 2×6
J2	1	PORT A	Pin Header 1×12
J3	1	PORT B	Pin Header 1×12
J4	1	PORT B	GPIO Connector 2×6

GPIO Card

Reference	Qty	Value	Description	LCSC
C1, C2	2	100nF	Unpolarized capacitor	C49678
D1	1	Schottky Diode	Schottky Diode DO-35
J2	1	IO SELECT	Pin Header 2×8
J3	1	PORT A	GPIO Connector 2×6
J4	1	PORT B	GPIO Connector 2×6
U1	1	74HC138	Decoder SOIC-16	C5602
U2	1	65C22	VIA DIP-40

GPIO Helper

Reference	Qty	Value	Description	DigiKey
D1–D8	8	LED	LED 3mm
J1	1	PORT A	GPIO Connector 2×6
J2	1	PORT B	GPIO Connector 2×6
R1–R8	8	1k	Resistor
R9–R16	8	330	Resistor
SW1–SW8	8	Push Button	Push Button 6mm	2223-TS02-66-50-BK-160-LCR-D-ND

Joystick Helper

Reference	Qty	Value	Description	DigiKey
J1	1	PORT	GPIO Connector 2×6
J2	1	DB-9 Male	DB-9 Connector (Male)	609-1481-ND
R1–R8	8	1k	Resistor

Keyboard Encoder Helper

Reference	Qty	Value	Description	DigiKey
C1, C4	2	100nF	Capacitor
C2, C3	2	22pF	Capacitor
J1	1	PORT B	GPIO Connector 2×6
J2	1	PORT A	GPIO Connector 2×6
J3	1	PS/2 KEYBOARD	6-pin Mini-DIN
J4	1	KEYBOARD	DB-25 Connector (Male)	609-1505-ND
R1	1	1k	Resistor
U1	1	ATmega1284-P	MCU DIP-40
Y1	1	16 MHz	Crystal HC49-U	3155-16M20P2/49US-ND

Keyboard Helper

Reference	Qty	Value	Description	DigiKey
J1, J2	2	JOYSTICK	DB-9 Connector (Male)	609-1481-ND
J3, J4	2	JOYSTICK	GPIO Connector 2×6
J5, J6	2	PORT	GPIO Connector 2×6
J7	1	KEYBOARD	DB-25 Connector (Male)	609-1505-ND
R1–R16	16	1k	Resistor
SW1–SW67	67	Cherry MX	Key Switch

LCD Board

Reference	Qty	Value	Description
C1–C4	4	100nF	Capacitor
D1, D2	2	Schottky Diode	Schottky Diode DO-35
J1	1	6502 Bus	Bus Connector 2×20
J2	1	IO SELECT	Pin Header 2×8
J3	1	HVSYNC	Pin Header 1×1
R1	1	10k	Resistor
U1	1	65C22	VIA DIP-40
U2	1	Adafruit 2.8" TFT	TFT LCD Module
U3	1	74HC138	Decoder DIP-16

LCD Card

Reference	Qty	Value	Description	LCSC
C1, C2	2	100nF	Unpolarized capacitor	C49678
D1	1	Schottky Diode	Schottky Diode DO-35
J2	1	GPIO	Pin Header 1×7
J3	1	IO SELECT	Pin Header 2×8
R1	1	R	Resistor
U1	1	65C22	VIA DIP-40
U2	1	LCD-16X2	16×2 Character LCD
U3	1	74HC138	Decoder SOIC-16	C5602
VR1	1	10k	Potentiometer

Mega Helper

Reference	Qty	Value	Description
A1	1	Arduino Mega 2560	Arduino Mega 2560 R3 Shield
J1	1	6502 Bus	Bus Connector 2×20

Memory Card

Reference	Qty	Value	Description	LCSC
C1–C5	5	100nF	Unpolarized capacitor	C49678
J2	1	Pin Header	Pin Header 2×2
J3	1	Pin Header	Pin Header 1×2
R1, R2	2	1k	Resistor	C17513
U1, U2, U5	3	74HC00	Quad NAND SOIC-14	C5586
U3	1	AS6C62256	SRAM DIP-28
U4	1	AT28C256	EEPROM DIP-28

Prototype Card

Reference	Qty	Value	Description	LCSC
C1–C3	3	100nF	Unpolarized capacitor	C49678
J2	1	Bus Header	Pin Socket 2×20
J3	1	EXP	Pin Header 2×4
U1	1	74HC138	Decoder SOIC-16	C5602

PS2 Helper

Reference	Qty	Value	Description
C1–C3	3	100nF	Disc Capacitor
C4, C5	2	22pF	Disc Capacitor
J1	1	PORT A	GPIO Connector 2×6
J2	1	PORT B	GPIO Connector 2×6
J3	1	PS/2	Mini-DIN 6-pin
J4	1	JOYSTICK	GPIO Connector 2×6
R1–R9	9	1k	Resistor
U1	1	MT8808	Analog Matrix Switch DIP-28
U2	1	ATmega328	MCU DIP-28
Y1	1	16 MHz	Crystal

RAM Card

Reference	Qty	Value	Description	LCSC
C1–C7	7	100nF	Unpolarized Capacitor	C49678
J2	1	LATCH EN	Pin Header 1×2
J3	1	Conn_02x08	Pin Header 2×8
J4	1	BANK ADDR	Pin Header 2×5
R1, R2	2	10k	Resistor	C17414
U1	1	AS6C4008	SRAM DIP-32
U2	1	74HC573	Octal Latch SOIC-20	C5608
U3, U6	2	74HC00	Quad NAND SOIC-14	C5586
U4	1	74HC21	Dual 4-input AND SOIC-14	C75398
U5	1	74HC30	8-input NAND SOIC-14	C19818870
U7	1	74HC138	Decoder SOIC-16	C5602

RTC Card

Reference	Qty	Value	Description	LCSC	DigiKey
BT1	1	BAT-HLD-001-THM	Coin Cell Battery Holder
C1–C3	3	100nF	Unpolarized Capacitor	C49678
D1	1	Schottky Diode	Schottky Diode DO-35
J2	1	AUX	Pin Header 1×6
J3	1	INT Select	Pin Header 1×3
J4	1	Conn_02x08	Pin Header 2×8
R1	1	1k	Resistor	C17513
U1	1	DS1511Y	RTC DIP-28		DS1511Y+-ND
U2, U3	2	74HC138	Decoder SOIC-16	C5602

Serial Card

Reference	Qty	Value	Description	LCSC	DigiKey
C1, C6, C8	3	100nF	Unpolarized Capacitor	C49678
C2–C5	4	1uF	Unpolarized Capacitor	C28323
C7	1	22pF	Unpolarized Capacitor	C1804
D1	1	Schottky Diode	Schottky Diode DO-35
J2	1	DB9 FEMALE (DCE)	DB-9 Connector (Female)		609-1487-ND
J3	1	Conn_02x08	Pin Header 2×8
J4	1	CTS EN	Pin Header 1×3
R1	1	1M	Resistor	C103906
U1	1	MAX232	RS-232 Driver/Receiver	C59824
U2	1	74HC138	Decoder SOIC-16	C5602
U3	1	6551	ACIA DIP-28
Y1	1	1.8432 MHz	Crystal

Serial Card Pro

Reference	Qty	Value	Description	LCSC	DigiKey
C1, C2, C11, C13	4	100nF	Unpolarized Capacitor	C49678
C3–C10	8	1uF	Unpolarized Capacitor	C28323
C12	1	22pF	Unpolarized Capacitor	C1804
D1	1	Schottky Diode	Schottky Diode DO-35
J2	1	DB9 MALE (DTE)	DB-9 Connector (Male)		609-1481-ND
J3	1	Conn_02x08	Pin Header 2×8
J4	1	DCD Select	Pin Header 1×3
R1	1	1M	Resistor	C103906
U1, U2	2	MAX232	RS-232 Driver/Receiver	C59824
U3	1	74HC138	Decoder SOIC-16	C5602
U4	1	6551	ACIA DIP-28
Y1	1	1.8432 MHz	Crystal

Sound Card

Reference	Qty	Value	Description	LCSC	DigiKey
C1, C2	2	2.2nF	Unpolarized Capacitor	C28260
C3, C5	2	100nF	Unpolarized Capacitor	C49678
C4	1	1uF	Unpolarized Capacitor	C28323
J2	1	VDD	JST XH 1×2
J3	1	AUDIO	RCA Connector		PJRAN1X1U02X
J5	1	Conn_02x08	Pin Header 2×8
R1	1	1k	Resistor	C17513
U1	1	6581	SID Chip DIP-28
U2	1	74HC138	Decoder SOIC-16	C5602

Storage Card

Reference	Qty	Value	Description	LCSC
C1, C2	2	100nF	Unpolarized Capacitor	C49678
D1	1	LED	Activity LED 0805	C2297
J2	1	Conn_02x08	Pin Header 2×8
J3	1	Compact Flash	CompactFlash Connector	C444350
J4	1	ACT LED	JST XH 1×2
R1–R4	4	1k	Resistor	C17513
R5, R6	2	330	Resistor	C17630
U1	1	74HC00	Quad NAND SOIC-14	C5586
U2	1	74HC138	Decoder SOIC-16	C5602

Storage Card Pro

Reference	Qty	Value	Description	LCSC	DigiKey
C1–C4, C7, C8	6	100nF	Unpolarized Capacitor	C49678
C5, C6	2	22pF	Disc Capacitor	C107114
C9, C10	2	1uF	Unpolarized Capacitor	C28323
D1	1	LED	Activity LED 0805	C2297
J1	1	ACT LED	JST XH 1×2
J3	1	SPI	Pin Header 1×6
J4	1	SD CARD	SD Card Connector	C569097
J5	1	Conn_02x08	Pin Header 2×8
R1, R2	2	330	Resistor	C17630
R3, R4	2	1k	Resistor	C17513
U1	1	TXS0108EPW	Level Shifter TSSOP-20	C17206
U2	1	ATmega328	MCU DIP-28
U3	1	W25Q128JVS	Flash Memory SOIC-8	C97521
U4	1	74HC138	Decoder SOIC-16	C5602
U5	1	LP2985-3.3	LDO Regulator 3.3V SOT-23-5	C95414
Y1	1	16 MHz	Crystal		3155-16M20P2/49US-ND

VERA Helper

Reference	Qty	Value	Description	DigiKey
C1, C2	2	100nF	Disc Capacitor
D1	1	Schottky Diode	Schottky Diode DO-35
J1	1	6502 Bus	Bus Connector 2×20
J2	1	VERA Module	Pin Header 2×12
J3	1	Audio L	RCA Connector	PJRAN1X1U02X
J4	1	Audio R	RCA Connector	PJRAN1X1U03X
J5	1	INT Select	Pin Header 1×3
J6	1	Conn_02x08	Pin Header 2×8
U1, U2	2	74HC138	Decoder DIP-16

VGA Card

Reference	Qty	Value	Description	LCSC
C1, C2	2	100nF	Unpolarized Capacitor	C49678
D1	1	Schottky Diode	Schottky Diode DO-35
J2	1	INT Select	Pin Header 1×3
J3	1	Conn_02x08	Pin Header 2×8
U1	1	Pico9918A	VDP Module DIP-40
U2, U3	2	74HC138	Decoder SOIC-16	C5602

VGA Card Pro

Reference	Qty	Value	Description	LCSC
C1–C6	6	100nF	Unpolarized Capacitor	C49678
D1	1	Schottky Diode	Schottky Diode DO-35
J2	1	VGA	DB-15 VGA Connector (Female)
J3	1	INT Select	Pin Header 1×3
J4	1	Conn_02x08	Pin Header 2×8
Q1	1	BSS138	N-Channel MOSFET SOT-23	C78284
R1, R2, R4, R7	4	1k	Resistor	C17513
R3, R6	2	2.2k	Resistor	C17520
R5, R8	2	470	Resistor	C17710
R9	1	820	Resistor	C17837
R10	1	390	Resistor	C17655
R11, R12	2	22	Resistor	C17561
U1	1	SN74LVC4245APWR	Octal Bus Transceiver TSSOP-24	C7859
U2	1	74LVC245	Octal Bus Transceiver TSSOP-20	C6082
U3	1	Raspberry Pi Pico	MCU Module
U4	1	74HC138	Decoder SOIC-16	C5602
U5	1	74LVC138	Decoder SOIC-16	C6061

Video Card

Reference	Qty	Value	Description	LCSC	Mouser	DigiKey
C1, C2	2	32pF	Disc Capacitor	C107114
C3–C10	8	100nF	Unpolarized Capacitor	C49678
D1	1	Schottky Diode	Schottky Diode DO-35
FB1	1	BLM41PG600SN1L	Ferrite Bead 1806	C85844
J1	1	INT Select	Pin Header 1×3
J3	1	Conn_02x08	Pin Header 2×8
J4	1	VIDEO	RCA Connector			PJRAN1X1U04X
Q1	1	2N4401	NPN BJT TO-92
R1	1	470	Resistor	C17710
R2	1	75	Resistor	C17820
U1	1	TMS9918A	VDP DIP-40
U2, U5, U6	3	74HCT574	8-bit Register SOIC-20	C6001
U3, U4	2	74HC138	Decoder SOIC-16	C5602
U7	1	AS6C62256	SRAM DIP-28
U8	1	74HCT04	Hex Inverter SO-14	C672096
Y1	1	10.738635 MHz	Crystal		774-MP107-E

Video Card Pro

Reference	Qty	Value	Description	LCSC	Mouser	DigiKey
C1, C2	2	20pF	Disc Capacitor	C105173
C3–C10	8	100nF	Unpolarized Capacitor	C49678
D1	1	Schottky Diode	Schottky Diode DO-35
FB1	1	BLM41PG600SN1L	Ferrite Bead 1806	C85844
J1	1	VIDEO	RCA Connector			PJRAN1X1U04X
J2	1	SERIAL	Pin Header 1×4
J3	1	INT Select	Pin Header 1×3
J5	1	Conn_02x08	Pin Header 2×8
Q1	1	2N4401	NPN BJT TO-92
R1, R2	2	4.7k	Resistor
R3	1	470	Resistor	C17710
R4	1	75	Resistor	C17820
R5	1	1k	Resistor
U1, U4	2	74HC157	Quad 2-to-1 Mux SOIC-16	C6823
U2, U5	2	74HC166	Shift Register SOIC-16	C473363
U3	1	ATmega1284-P	MCU DIP-40
U6	1	74HC138	Decoder SOIC-16	C5602
VR1, VR2	2	10k	Potentiometer
Y1	1	14.31818 MHz	Crystal		774-MP107-E

Purchase

I have a few PCBs available on Tindie for those interested in building their own AC6502 system without ordering from a fab directly.

License

Hardware designs are released under the CERN Open Hardware Licence Version 2 – Permissive.
Firmware is released under the MIT License — KEH Controller, PS2 Keyboard Controller, STP Controller.