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ACSI2SD has been ICD compatible since 2022

ATARI ST with Megafile, ACSI2SD Proc V1.0

ATARI ST gets ready for a long life.

And for you hands-on experience with a modern ARM Cortex M3 microcontroller.

ACSI2SD is an ACSI harddisk (Megafile 30/60/44, SH204, SH205) emulator, initially available as a kit only.

The old hard drive with mechanical elements is replaced by a removable MicroSD card as medium. Because of very low power consumption ACSI2SD can be powered by your ATARI (housing must be opened) or by means of al 5V power supply with a standard 5,5/2,1mm dc plug (not included). You can also feed the 5V via Mini-USB into ACSI2SD Kit Proc (suitable power supply in the shop) and via Micro-USB into ACSI2SD Kit Mod.

ACSI2SD Kit Proc is smaller than 5 x 5 cm and is plugged directly into the DSub19 ACSI-connector. The connector consists of 19 terminal pins in order to avoid a wide gap between the ATARI ST housing and the PCB. ACSI2SD Kit Mod is larger and stands more off from the housing as it uses the rare DSub19 connector.

ACSI2SD uses a Cypress PSoC5LP mixed-signal microcontroller.

The integrated development environment PSoC Creator for Windows can be downloaded for free from Cypress.

ACSI2SD is open source under the GPL license. Hardware (schematic) and software (annotated C source code, PSoC Creator Files) are published on Github.

ACSI2SD covers the hardware side of the project: You will need a Harddisk Driver (a DiskImage is a convenient solution) on your microSD card. Free and commercial Atari HD Drivers exist. Please gather information before you buy. We can't offer advice, but we provide some useful links about HD Drivers below. 

NEW: ACSI2SD Kit Proc V1.0 ships with the pre-programmed controller (latest software revision), so that you don't have to start with the Plus-version if you don't have your own programmer! ACSI2SD Kit Mod Easy V1.0 contains also a programmed module.

TIP: Get to know the project first, then order. The kits only contain the components and a parts list, the essential information is linked here.


ACSI2SD Kit Overview

Design files on Github

Cypress PSoC Creator IDE

Assembly Guide (en)

ACSI harddisk driver information (en)

Image with PP harddisk driver (en)

Image with ICD harddisk driver (en)

Image with HDDRIVER harddsik driver Demoversion (en)

Firmware Updates

What can I learn from studying ACSI2SD?

Please read before you contact us

 Would you like to participate in the ACSI2SD project?

Upgrade the firmware and with a bit of luck you could win a kit (ACSI2SD or SCSI2SD)!

In our Cypress PSoC, about half of the resources are still idle. And the following task fits the year 2022: Expand the firmware for a second micro SD card. The cards should be addressable independently of each other, including copying from one card to another. If we like your firmware extension, it will become part of our repository on Github, then we will thank you with a kit of your choice (free shipping only within the EU)

Here are the rules:

  • Promotion period 22.02.2022-22.02.23. Not the fastest entry wins, but the best.

  • Rules may also be adjusted during the promotion period, but entries prior to a rule adjustment will remain eligible

  • You take part in the competition by electronically sending us the necessary PSoC Creator Files (e.g. .cysch, .cydwr, .c, .h) with the keyword "2022 Programming Contest" so that a build with these files in the current PsoC Creator version is possible (no errors, but warnings allowed), please only send in changed files, the .hex file can also be sent in

  • You can submit the firmware extension for either ACSI2SD Mod or ACSI2SD Proc

  • As usual, you can name yourself as author/co-author in the header of the program code, but you don't have to

  • All submitted material must be free of third-party rights

  • The legal process is excluded.

    What is evaluated positively?

    • as few changes/extensions as possible, if possible in the existing files

    • Kommentare möglichst im Einklang mit dem bestehenden Sourcefiles

    • a good division between implementation in hardware (UDB area) and software

    K.O. criteria

    • under no circumstances additional hardware outside of the PSoC, but the existing solder jumper J may be used

    • no additional utilities, the modules should still be configurable with SCSI2SD-util and testable with SCSI2SD-monitor (the 2nd Micro-SD does not have to be testable)

    • under no circumstances claim all ACSI IDs yourself (there could be an ACSI hard disk or a laser printer with ACSI ID 7 in the ACSI chain)

    The hardware connection of the second micro SD is published in circuit diagrams on Github. During the promotion period we plan to support you with cheap PCBs for the double SD version. If you buy an ACSI2SD kit, you can also order such a PCB free of charge.

Become creative and make a video of assembling one of our kits.

You let others watch while crafting and we thank you for your video with a free kit of your choice (ACSI2SD or SCSI2SD)!


Why shouldn't a buyer of our kits let the camera run along when building our kit? Sprinkle in a few tips when it gets difficult, critically examine our concept and finally show the finished product.


If you want to inspire us and others, make a video and send us a link. Once it convinces us, we will include it on our website, then we thank you with a free kit of your choice (free shipping only within the EU).


Here are the rules:

  • Promotional period until Dec 31, 2021. Not the fastest video wins, but the best.
  • Rolling principle: A good video can be replaced by a better one or stand side by side, both submitters will be rewarded when they are published
  • common video format, recommended length 5-15 min
  • Language and / or subtitles: German or English
  • Multiple opportunities: Each of our 4 kits is qualified x 2 languages ​​= 8 chances of winning
  • no self-portrayal: the presenter should not appear face-to-face in the video and not disclose any personal data (first name and nationality allowed)
  • If the sender agrees to the publication, he must provide us with a copy of the video or the link to third party websites must be available for at least one year.
  • Jurisdiction of a court is excluded.