Sorbus VGA

The Sorbus Computer

The attempt to build a very simple 65C02 based computer by utilizing a Raspberry Pi Pico clone for the rest of the functionality. More documentation is available at https://sorbus.xayax.net/.

The Project is capabile to run as an Apple Computer 1 as well as an own monitor command prompt (mcp) to learn about the 65C02 processor and it siblings. However now the main focus is now on creating a custom computer, using a code called "JAM" (Just Another Machine).

The project is fully open source, licensend under GPL v3:

• the PCB design is in the folder pcb/
  • the Raspberry Pi Pico clone is found under the term "Purple PR2040" on AliExpress and other sites
  • the clone is used because all GPIOs of the RP2040 are required
• the 65C02 source code to run on the target is at src/65c02/
  • compiling requires the cc65, which needs to be preinstalled.
• the source code for the Raspberry Pi Pico clone is at src/rp2040/
  • compiling requires the Pico-SDK from the Raspberry Pi Foundation, which will be downloaded if not previously configured. However it's dependencies must also be preinstalled.
• for generating the CP/M-65 filesystem cpmtools is also required

An addtional page has been setup to explain more about the ideas of the system, as well as some usecases.

Also there is now an independent review available at the wonderful Retro Computing pages of Hans Otten.

As part of creating a full featured computer, there are also two expansion boards developed here: a sound card, called "Sorbus Sound" and a graphics card, called "Sorbus VGA".

To access the RP2040 without super user rights, make sure that your user is in the groups "plugdev" and "dialout". You also need to add a udev rule. This is available as part of picotool in the udev folder.

Build Targets

The toplevel Makefile is added as a convenience layer to build things more easily. It wraps the call of cmake and make to configure the Raspberry Pi Pico project, as well as some other useful things. The following make targets are available:

• make all
  • checks for availablilty of the Pico SDK and downloads it, if required
  • creates a new build directory
  • wraps the call to cmake and make to build the project
• make log
  • almost same as "all"
  • more verbose compilation, e.g. compiler calls with parameters
  • creates a file make.log
• make clean
  • runs a make clean on build directory
• make distclean
  • removes build directory entirely to force restart from scratch
• make setup-apt
  • installs packages on Debian required to build the project
  • used by git actions to prepare building of a release
• make setup-dev
  • runs "setup-apt", as well as doing modifications to make sure that terminal and picotool work
• make picotool
  • checks out and builds picotool
• make setup-external
  • sets up tools required to build external code, like
    • CP/M 65 (requires llvm-mos-sdk)
    • TaliForth2 (requires 64tass)
• make release
  • used by git action to build a release

There are also some build scripts available for special cases:

• src/tools/upload.sh
  • script used to build and transfer software using picotool (needs rewrite)
  • defaults to uploading the JAM core
• src/tools/external-taliforth2.sh
  • script to checkout, build and install the TaliForth2 binary ready for building the filesystem image
  • only required for native core
• src/tools/external-cpm65.sh
  • script to checkout, build and install the files required to include CP/M 65 into the filesystem image
  • only required for native core

It is also possible to build C programs using cc65 for this computer. This is rather a proof of concept that a full featured implementation, but it does work rather stable. More details are in it's own README.