CrO2 USB tape storage emulator

The CrO2 is an emulator for the MO5 storage device, a tape drive.

The MO5 is a french microcomputer made by Thomson. The tape drive for this computer is not standard, as it performs signal cleanup and part of the decoding itself (with analogue electronics), and the communication with the computer is done at TTL levels. This make it very easy to replace the tape drive with an AVR microcontroller.


  • Loads unprotected programs from a PC computer straight to the MO5
  • No read error problems
  • Up to 30% faster than standard tape drive with standard MO5 load code

Planned features


  • Super-fast mode with direct TTL access and no modulation, for high-speed file transfers (needs dedicated MO5 loader).
  • Save from MO5 to PC
  • Load and save protected formats
  • Easy-to-use UI (graphical and command line) for host software
  • Host software for at least linux and windows.
  • Load RAW file and create tape-blocks from it automatically

Misc tech info

  • signal generation done using timer 1 in CTC mode and interrupts. Leaves CPU free to handle USB communication.
  • USB done with (of course) the V-USB stack
  • USB communications only on the default control endpoint
  • byte-level transfer on USB
  • Use V-USB dev board with no modifications
  • Host software loads K5/K7 files and extract blocks (shortens sync header, fix checksums)

Host software

Developped in the thomson area if you're after sourcecode.

  • Uses IUP toolkit, portable on Windows and UNIX (GTK or Motif)
  • Provides control of the emulator, and also tape file exploration
  • Loads MO5 K5 tape files

Planned features (NOT READY) :

Screenshot of host software

Last modified 8 years ago Last modified on Nov 17, 2015, 2:36:55 PM

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