Programming:Cross Development

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Introduction

Cross development is a development method where you use another machine (the host) to develop programs for the CPC (target). This is interesting because you can make a big program which sourcecode does not even fit on the CPC ram.

The main drawback is that transferring the compiled code to the CPC can be quite difficult. But there are pretty good emulators which you can use for testing.

Once you have your binary file you have two choices depending on if the game will be for cassette or disc.


  • Atari ST was a common 16 bit computer actually used in cross development of games on CPC.

Of course nowadays cross development use far more powerful modern computers.

Tools needed for cross development

Integrated toolchains

An integrated cross-development toolchain is a time saver for development as it automates all necessary steps from a full set of source materials (source code, graphics, music, parameters in whatever format is practical for editing, etc) to one or several formats ready to run on the target machines. It also sometimes includes automatically launching or notifying an emulator or target device. See e.g. Build Automation on wikipedia.

Such a design has several advantage:

  • allows the usage of any text/graphic editor of modern platforms
  • you can change anything in one or more source files and you get an updated build quickly without error-prone manual steps
  • allows arbitrary transform or generation of intermediary files (code or data).
  • makes easy to have specific builds (e.g. for automated tests like to check if a different compiler produces correct code, variant build for slightly different targets)
  • since most material are text files or small independent files, it benefits hugely from modern tools for revision control like Git which makes sharing and merging code between developers much easier, increasing the time saved.

An ideal toolchain does not force its user into specific ways of doing things but is flexible enough to let the user adjust for whatever specific needs (use different languages, compilers, linkers, etc). Along with a properly designed and structured source tree, this makes projects less dependent on specific tools used to build them, and be more resilient to bit rot due to software build environment change.

Please note that an integrated toolchain has little to do with anything visible on-screen. A good toolchain can be triggered by most flexible enough graphical environments and generally produces a text log of the work done. Nevertheless, the concept of toolchains is more natural to Linux/Unix way of thinking/doing things, and those environments are already full of reusable and combinable tools that ease the creation and maintenance of a toolchain. Windows users can generally use tools developed for Unix through the cygwin software adaptation layer but running a Linux distribution in a virtual machine may be more practical.

There are some attempts at creating toolchains targeting the CPC.

Active as of 2017-11:

  • CPCtelera integrates an out-of-the-box preconfigured build system, along with a game development library and tools. It is also multiplatform, working on Linux, OSX and Windows.
  • cpc-dev-tool-chain integrated C or ASM development toolchain for the Amstrad CPC platform (or emulator). Includes compiler, assembler, makefile-based projects, interface between C and firmware. Designed for quick start on Linux (or similar) systems : get a copy, run "make" and get a DSK ready to run into the emulator. It even downloads and compiles tools (the cross-compiler, iDSK) if needed. Made for Linux, also works with Windows (via cygwin or similar), and probably Mac OS X. Most project+build-oriented features claims by CPCTelera comes from cpc-dev-tool-chain.
  • Not an integrated toolchain, but a collection of tools that can be strung together to make one, including a DockerFile. Mentioned on CPC SDK for Linux/Unix. Appears to have moved to https://github.com/cpcsdk

Linux

Cartridge management

Cross assemblers

Cross compilers

Crunching

Disassemblers

Disc management

Editing

  • scite
  • pico
  • xemacs
  • Vim
  • pluma
  • gedit

Emulators

Tape management

Toolkits

  • CPCSDK toolkit which contains useful tools for cross-development under Linux - [17]

Useful scripts

Suppress header information of a file

cat file_with_header | tail -c+129 > file_without_header

Needed Tools

These tools have to not require a lot of requirement and most of them must work in command line without GUI. This will allow to use them with Makefile scripts. They have to be fast too, it will be disappointing to wait more when doing CrossDev than when doing code on a real CPC. A good thing (like most of CPCTools) is to have a portable code which compile on most platforms.

  • a good emulator which can be integrated in other tools. (Ramlaid first try to change Caprice is a good start)
  • an integration of Ramlaid's tools with Nautilus
  • ameliorations of Caprice in order to have similar functionalities than WinApe (disasm, asm, ...)
  • debug the libdsk which seems to work very bad on actual computers (writting fail a lot)
  • a lot of macros, or libraries for SJASMPlus shared by people in order to share code
  • share a generic Makefile able to be use for build CPC project
  • a lot of little command line utilities (could be add to CPCTools ?) really well done  :
    • graphics tools :
      • convert images from PC to CPC, or CPC to PC (cf. tools based on ImageMagick or GD)
      • equivalent of Anoine's FontCatcher
    • 2 tools which work with BASIC :
      • one for create BASIC AMSDOS files from ASCII or UTF-8 text files
      • one for create ASCII or UTF-8 text files from BASIC AMSDOS files
      • (this can already be done with manageDSK for files inside a DSK, maybe extract the code from there)
    • data manipulation tools :
      • ability to arrange data files for example modify bytes order in a picture file by using Gray code capabilities for changing line with modifying 1 bit

Windows

Cross Assemblers

Cross compilers (C)

For tutorial, see http://www.cpcmania.com/Docs/Programming/Programming.htm by Mochilote

Cross compilers (Java)

WIP

Graphics

  • AMSprite - Sprite/Loading Screen Editor and graphics conversion tools

Sound

Testing on a real CPC

For cassette

  • 2CDT to add the files to a Cassette Image File (CDT)
  • Tape2WAV to convert the Cassette Image file (CDT) into a WAV file.
  • Then you can run the program on the emulator the same way as you would run it on a real CPC, or
  • Connect your CPC (CPC664 and CPC6128 have a cassette input) to the Line-Out output of your PC soundcard
  • On the CPC type:
|TAPE:RUN"
  • Start your WAV player
  • Set the volume to maximum
  • play the WAV file
  • Wait for the program to load...

For disc

  • Use CPCFS or CPCXFS to put the binary files into a Disk Image file (DSK)
  • Then you can run the program on the emulator the same way as you would run it on a real CPC

If your CPC has a 3.5" disc drive then the easiest method is to transfer the DSK to a 3.5" disc using a PC with a 3.5" drive (internal, not USB).

  • Then write the DSK to a 3.5" disc drive, using dsktools (Linux) or CPCDiskXP (Windows).
  • Put the disc into your CPC's 3.5" disc drive and type - |B: RUN "<gamename>

Snapshots

The fastest way of testing your code on an emulator is by creating a snapshot. Use CPCSnapshot to insert your assembled code into a snapshot file. Then just load the snapshot file into the emulator. Windows users may also try WinAPE's integrated assembler which assembles the code directly into the emulated CPC's memory.

Web links