esp8266-ntsc-c64-emulator

C64 emulator running on the ESP8266 with NTSC video output and PS/2 keyboard input.

Original author: Jan Ostman. Published November 12, 2018 on https://www.hackster.io/janost/esp8266-ntsc-c64-emulator-b91a35 under GPL3+.

Enhancements by Matthias Goebl at https://github.com/matgoebl/esp8266-ntsc-c64-emulator/

• PS/2 keyboard input with hotkeys
• Cursor display
• Wifi and OTA update
• Load builtin PRGs with hotkeys

Limitations

This simple emulator is a proof-of-concept.

It only emulates the 6502 CPU of a C64 with basic video output for PETSCII characters.
It lacks emulation of the SID chip for sound output and the VIC chip for sprites and graphics output.
It provides only 16KB of RAM (C64 has 64KB), it shows 14335 basic bytes free (C64: 38911 bytes free).
There is no joystick support, only keyboard input into the basic keyboard buffer, so many assembly programs that access hardware keyboard registers wont work.
Therefore it is only usable for short commodore basic programs with PETSCII output and no PEEKs and POKEs.

Used libraries

The following arduino esp8266 packages are needed:

• WiFiManager
• ArduinoOTA
• PS2Keyboard

PS2Keyboard requires a small fix: Add the following lines to packages/esp8266/hardware/esp8266/2.4.2/variants/generic/common.h:

#ifndef CORE_INT_EVERY_PIN
#define CORE_INT_EVERY_PIN
#endif /* CORE_INT_EVERY_PIN */

OTA mode

Add your wifi ssid and psk to wifi_credentials.h. Press escape within 1 second after ESP full reset (power-on or shift-escape). ESP will then enter wifi OTA mode. Press shift-escape again to boot to C64 mode.

Keyboard layout

I used an old PS/2 keyboard with a german layout, for other layouts you have to adapt PS2Keymap_German_c64.

The following keys have a special function:

Key	Function
Scroll-lock	Pause on/off
Esc	C64 reset
Shift-Esc	ESP full reset
Tab	Run
Shift-Tab	Stop
Shift-F1 .. Shift-F12	Load builtin PRG #1 .. #12

How to compile-in PRGs

• create e.g. hello-world.bas
• compile basic source into token: petcat -w2 -o hello-world.prg hello-world.bas (petcat comes with VICE
• convert binary into a C include file: xxd -i hello-world.prg > hello-world.h
• adapt hello-world.h: change unsigned char into const PROGMEM unsigned char

This is automatically performed by the script prg/prg2h.sh, that creates ESP8266-NTSC-C64/builtinprg_X.h.

For extracting PRGs from a D64 file use c1541 -attach *.d64 -extract.

Hardware circuitry

Video signal

This adaptor generates the CVBS video output signal from ESP RX pi. When connected, flashing via serial doesn'n work - that's the reason OTA has been added.

PS/2 keyboard

This simple level shifter limits the 5V output from PS/2 keyboard to 3.3V ESP inputs:

PS/2 Data  -----<|----- ESP D3
              1N4148

PS/2 Clock -----<|----- ESP D2
              1N4148
(some keyboards might need an additional pullup to 5V at keyboard side)

Audio output

Audio output is so far only used for beep output at startup, no SID emulation yet.

GND -------#####---------||----- ESP D1
        Mini-Speaker     4u7

Builtin PRGs for demonstation

When looking for suitable demonstration programs, I found the BASIC 10Liners contest:

• It allows only short basic programs with no assembler and limited POKEs.
• I found several programs with keyboard input and PETSCII output.

There is no well-known open source license given for the 10liners, however the authors agreed on publication of the source code.

I added my selection of working games into the folder prg/.
This set is automatically built into the emulator and quickly loaded by pressing function keys (shift + F1..F12).

1. 10 Print

A one-liner that prints a labyrinth. https://10print.org/

2. Mini Tetris

by marcosj, Buenos Aires, Argentina

Keys: A S D

posted on https://www.lemon64.com/forum/viewtopic.php?t=30998 ( public domain according to gamebase64 )

edited: changed rnd(0) to rnd(1)

3. Snake

by Davide Fichera @Naufr4g0 (assumed, as this is also available here pointed from https://twitter.com/naufr4g0

Keys: A D

Downloaded from basic 10liners 2016 for C64 and NOMAM2016 Dropbox

4. GorillaX

by Davide Fichera @Naufr4g0

Keys: enter number, return

Downloaded from basic 10liners 2017 for C64 and Dropbox

5. Beer Hunter

by Sander Alsema

Keys: , . space

Downloaded from basic 10liners 2017 for C64 and Dropbox

6. Bomber

by Georg "Endurion" Rottensteiner

Keys: Space

Downloaded from basic 10liners 2018 for C64 and Dropbox

7. Last Outpost

by 5ace

Keys: Left Right

Downloaded from basic 10liners 2018 for C64 and Dropbox

8. Duck!!!

by Sander Alsema

Keys: J D

Downloaded from basic 10liners 2018 for C64 and Dropbox

9. Egg Collector

by Sander Alsema

Keys: , .

Downloaded from basic 10liners 2018 for C64 and Dropbox

10. EasterShip

by Logiker

Keys: none, just watch demo

Downloaded from basic 10liners 2018 for C64 and Dropbox

11. Hello World

just to fill empty slots.