Analogue Pocket - MyC64

The MyC64 core is my go at writing a FPGA based C64 emulator. It is a project I started during the summer of 2020, at that point targeting the ULX3S board. Initially it made good progress but then nothing happened for a long long time.

Years later the Analogue Pocket came along with its openFPGA framework and slightly after Christmas 2023 I decided to get started on its current incarnation.

What can it do?

Have a look at this Youtube playlist (that I will try to keep up-to-date when something noteworthy is added).

In short though, the core is still work-in-progress but quite a lot of things actually do work (plus minus some emulation discrepancies).

Setup instructions

Simply unzip the MyC64-Pocket.zip (from releases) in the root directory of the Analogue Pocket's SD card.

System ROMs

For legal reasons all ROMs are kept outside the FPGA bitstream distributed here. The Commodore ROMs (three for the C64 and two for the 1541) can be fetched with

wget http://www.zimmers.net/anonftp/pub/cbm/firmware/computers/c64/basic.901226-01.bin
wget http://www.zimmers.net/anonftp/pub/cbm/firmware/computers/c64/characters.901225-01.bin
wget http://www.zimmers.net/anonftp/pub/cbm/firmware/computers/c64/kernal.901227-03.bin
wget http://www.zimmers.net/anonftp/pub/cbm/firmware/drives/new/1541/1540-c000.325302-01.bin
wget http://www.zimmers.net/anonftp/pub/cbm/firmware/drives/new/1541/1541-e000.901229-01.bin

they then need to be placed in /media/Assets/c64/common/ as follows

/media/Assets/c64/common/basic.bin
/media/Assets/c64/common/characters.bin
/media/Assets/c64/common/kernal.bin
/media/Assets/c64/common/1540-c000.bin
/media/Assets/c64/common/1541-e000.bin

Supported formats

All assets are to be placed in /media/Assets/c64/common/ or sub-directories thereof.

PRG

Standard .prg files are supported.

Select the desired .prg file from the Core Settings->Load & Start PRG and the following sequence will be initiated

Core resets
Wait 2.5s (until booted)
Inject .prg into RAM
Inject a RUN<RET> key sequence

Suggestions are Supermon+64 and the High Voltage SID Collection (HVSC) converted to PSID64 format.

For games it is recommended to get hold of the OneLoad64 collection of 2100+ titles OneLoad64-Games-Collection-v5.7z (just google it). From what I can tell the majority of the collection's crunched .prg files (found in AlternativeFormats/PRGs/Crunched/) load up properly. It is important to pick the crunched ones as the uncrunched will attempt to replace the entire RAM which is not supported while the system is running.

The Pocket appears to truncate directories containing more than 1500 files so indexing as below is suggested.

$ p7zip -d OneLoad64-Games-Collection-v5.7z
$ cd AlternativeFormats/PRGs/Crunched/
$ for letter in {a..z}; do mkdir ${letter^}; mv ${letter}*.prg ${letter^}/; mv ${letter^}*.prg ${letter^}/; done
$ for digit in {0..9}; do mkdir ${digit}; mv ${digit}*.prg ${digit}/; done

Of course as the core is in development not every .prg will function correctly. So to avoid frustration and help new users out we have the following wiki page Working PRGs that anyone (on github) can edit. Please feel free to update it with your findings!

CRT

Currently the following cartridge formats are supported

Magic Desk - as defined in the .crt format specification. This is the main format used by the .crt files in the OneLoad64 games collection. The cartridge is limited to 128KB of storage.
EasyFlash - as defined in EasyFlash Programmer’s Guide. The secondary format used by some of the larger games in the OneLoad64 collection. A modern cartridge that can hold up to 1MB of storage. Seemingly the preferred cartridge format for new content.

Select the desired .crt file from the Core Settings->Load & Start CRT browser. The emulated cartridge will be inserted into the system and the C64 is automatically reset to boot up its contents.

Cartridges of unsupported formats are silently ignored (and no reset is triggered).

D64/G64

The core contains emulation of a Commodore 1541 floppy disk drive (currently read-only). Emulation is low level and the real ROMs are used. As a result the decode circuitry need to have the raw GCR bitstream (that the read head of a real drive would see) as its input.

In other words the common .d64 format is not directly supported but rather the lower level .g64 format must be used.

A bit further down the road the housekeeping CPU could probably perform this conversion on the fly but right now .d64 files need to be converted to .g64 format manually.

The utility program nibconv from NIBTools can be used to convert between .d64 and .g64.

Usage example:

$ nibconv somedisk.d64 somedisk.g64

Obtaining nibtools

Windows

You can download pre-build binaries for windows from c64preservation.com files.

Linux

For Linux it is obtained and built as follows

$ git clone --recurse-submodules https://github.com/OpenCBM/OpenCBM.git
$ cd OpenCBM
$ make -f LINUX/Makefile

MacOSX

On MacOSX you can auto-build nibtools using Homebrew and hitorisensei/homebrew-taps/nibtools tap

$ brew install hitorisensei/homebrew-taps/nibtools

Loading G64 images

Select the desired .g64 file from the Core Settings->Load G64 Slot browser and the disk image will be inserted into the emulated 1541 floppy drive.

At this point the user needs to do normal interaction such as LOAD"$",8 followed by a LIST to get a directory listing or simply a LOAD"*",8 followed by a RUN to load and run the first program of the disk.

Note that on the C64 keyboard " is <SHIFT>+2 and $ is <SHIFT>+4 (read the section about sticky keys for how to access the shift modifier on the virtual keyboard).

General usage

The gamepad is mapped to the C64 joystick port as follows

dpad - as expected
face-a - fire button
face-b - second fire button
face-x - third fire button

Pressing left-of-analogue brings up (toggles) the on-screen-display containing a virtual keyboard and a small menu system for settings.

For the virtual keyboard the face-x button toggles sticky keys (useful for modifiers such as shift) and the face-y button clears any sticky key. Normal key press is accomplished with the face-a button.

Pressing trig-l1 and trig-r1 navigates through the different menu tabs.

Controllers can be mapped to C64 joystick ports in the MISC menu tab and there you will also find a reset button for the emulator core.

A physical keyboard is supported while docked. The keyboard is expected to show up on the third input (i.e. cont3_joy). For details on the key mapping see table hid2c64 in source file src/bios/main.c.

markus-zzz/myc64-pocket