Deck65

Homebrew 6502-based single-board computer with WiFi, built-in mechanical keyboard, uSD card adapter, I2C/SPI, EEPROM, & RTC.

Deck65 SBC

New discussion: http://forum.6502.org/viewtopic.php?f=6&t=7682
Original thread (old SBC version): http://forum.6502.org/viewtopic.php?f=12&t=7501

Pull with git pull --recurse-submodules.

Memory map

+--------------+-------+------------------+------+------------------------------------------+
| RANGE        | TYPE  | ADDR             | SIZE | Notes                                    |
+--------------+-------+------------------+------+------------------------------------------+
| $0000..$0FFF | RAM   | 0000------------ | 32 K | /EN = A15                                |
| $1000..$1FFF |       | 0001------------ |      | $0000..$1000 - zeropage & video buffer   |
| $2000..$2FFF |       | 0010------------ |      | $1000..$7FFF - programs from SD Card     |
| $3000..$3FFF |       | 0011------------ |      |                                          |
| $4000..$4FFF |       | 0100------------ |      |                                          |
| $5000..$5FFF |       | 0101------------ |      |                                          |
| $6000..$6FFF |       | 0110------------ |      |                                          |
| $7000..$7FFF |       | 0111------------ |      |                                          |
+--------------+-------+------------------+------+------------------------------------------+
| $8000..$8FFF | LOROM | 1000------------ | 16 K | /EN = NAND(A15, NAND(A14))               |
| $9000..$9FFF |       | 1001------------ |      | Contains OS ("MicroREPL")                |
| $A000..$AFFF |       | 1010------------ |      |                                          |
| $B000..$BFFF |       | 1011------------ |      |                                          |
+--------------+-------+------------------+------+------------------------------------------+
| $C000..$CFFF | N/C   | 1100------------ | 4 K  | Unused, may add extra '138 with /GA=/A13 |
+--------------+-------+------------------+------+------------------------------------------+
| $D000..$DFFF | I/O   | 1101------------ | 4 K  | G = A12, /GA = A13, /GB = NAND(A15, A14) |
|              |       | 1101-000-------- | 256B | $D000..$D0FF - RAM banking register      |
|              |       | 1101-001-------- | 256B | $D100..$D1FF - 6522 VIA                  |
|              |       | 1101-010-------- | 256B | $D200..$D2FF - 6551 ACIA                 |
|              |       | 1101-011-------- | 256B | $D300..$D3FF - T6963C LCD (240x64)       |
+--------------+-------+------------------+------+------------------------------------------+
| $E000..$EFFF | HIROM | 1110------------ | 8 K  | /EN = NAND(/NAND(A15, A14), A13)         |
| $F000..$FFFF |       | 1111------------ |      | Contains Kernel ("Kore")                 |
+--------------+-------+------------------+------+------------------------------------------+

LOROM (10xx) || HIROM (111x):
/EN = A15 && (/A14 || (A14 && A13))
/EN = NAND(A15, /A14 || /NAND(A14, A13))
/EN = NAND(A15, NAND(A14, NAND(A14, A13)))

Features

W65C02, 512 KB RAM (32KB visible to CPU, banked into 4 x 8 KB segments)
240x64 LCD display (T6963C)
Built-in mechanical PS/2 keyboard, powered by ATmega328P
Internet! Works through ESP-01
VIA W65C22<ins>N</ins>(6TPG-14)

Provides:
- SPI (used for Micro SD Card adapter)
- I2C (used for RTC & EEPROM)
- PS/2 host (used for built-in or external keyboard)
ACIA W65C51<ins>N</ins>(6TPG-14)n

Provides:
- Communication with ESP-01
- Communication with external devices through pin header
Note: I'm using NMOS-compatible versions of VIA & ACIA (<ins>N</ins> suffix) with open-drain /IRQ line. See http://archive.6502.org/datasheets/wdc_w65c22_sep_13_2010.pdf (page 25) for more details.
Address decoder & underclocking - ATF16V8B-15PU

Main crystal is 16 MHz, and the CPU runs at either 8 MHz or 2 MHz. Reason for this is that T6963C LCD can only operate on up to 2.75 MHz. So when CPU needs to acccess the LCD, ATF16V8 divides clock speed by 4, bringing it down to 2 MHz. This is done by implementing a 2-bit counter using registered outputs.
Memory banking: 74LS670

Entire RAM (first 32 KB) is divided into 4 x 8 KB segments. Each segment can use one of its own 16 banks. This allows to selectively bank parts of RAM in and out. Using a machine-tooled socket actually allows to connect JCO-8 or JCO-14 oscillators.
Traco Power TSR 1-2450 (drop-in replacement for 7805)

It runs much cooler than L7805 since it's a switching regulator. I use them a lot, although they are not as cheap as 7805.

V2.0 schematic: 65c02s SBC PCB

ROM

Kernel code currently provides the following features:

Simple REPL shell to monitor memory & run programs
128x64 LCD (through VIA)
PS/2 keyboard (through VIA)
Micro SD Card in SPI mode (through VIA)
I2C & SPI support
Basic FAT16 support - listing root folder, loading/executing programs

Resources

Kicad files - https://www.kicad.org/
DipTrace PCBs - https://diptrace.com/
Circuits (created with Digital)
ROM sources (written in 6502 Assembly, requires cc65 compiler)
SD Card programs (written in 6502 C, requires cc65 compiler)
Keyboard firmware (written in C)
GAL stuff (hexadecimal 7-segment decoder, address decoder, etc using GAL16V8/GAL20V8, includes galasm as submodule)
Composite video test using ATtiny45 (requires avra)

So what can you do with it?

Playing snake, for example:

Credits & references

6502.org community - Limitless help & support
https://www.masswerk.at/6502/6502_instruction_set.html
https://github.com/4x1md/kicad_libraries - Mini-DIN-6 symbol & footprint
http://39k.ca/reading-files-from-fat16/
https://laughtonelectronics.com/Arcana/KimKlone/Kimklone_opcode_mapping.html - cool illegal NOPs
https://octopart.componentsearchengine.com/part.php?partID=570717&ref=octopart - Aries 28-526-10 footprint
https://github.com/daprice/keyswitches.pretty - MX switches
https://components101.com/sites/default/files/component_datasheet/Micro-SD-Card-Module-Datasheet.pdf - MicroSD card module datasheet & dimensions
http://static.cactus.io/docs/sensors/temp-humidity/mcp9808/25095A.pdf - MCP9808 I2C temperature sensor
https://ww1.microchip.com/downloads/aemDocuments/documents/MPD/ProductDocuments/DataSheets/24AA512-24LC512-24FC512-512K-Bit-I2C-Serial-EEPROM-20001754Q.pdf

Deck65

Install / Use

README

Deck65

Memory map

Features

ROM

Resources

So what can you do with it?

Credits & references

Links