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SIO2PC USB Interface

SIO2PC Universal Interface

USB Edition Setup Documentation

©2015 Steven J Tucker



Your SIO2PC USB interface is, by necessity, more sophisticated than a standard RS232 adapter.

Your interface is actually a complete embedded system containing:

While every effort has been made to make the interface as simple to maintain and operate as a standard SIO2PC Universal interface, there are some differences.

Please note that the information below is somewhat technical and possibly very boring if all you want to do is get started. If that's the case, continue on now to Chapter 1 - Software Installation.

Real Time Performance

APE on OSX w/ USB Interface

SIO2PC relies very heavily on near real-time performance in order to operate properly.

With a standard SIO2PC adapter, the real-time requirements fall entirely on the software operating the interface. Should the software or host OS become too busy to answer SIO queries, bus errors and other SIO problems start to occur.

The USB interface removes this burden from the host SIO2PC software, achieving excellent SIO performance in situations where regular SIO2PC performs poorly or simply will not work at all.

For example, it is possible to make use of the SIO2PC USB interface under virtualization software like VMWare and Parallels.

Click on the thumbnail to the right to see a larger screen shot of APE for Windows running on OSX via Parallels with the USB interface.

This relaxation of the real-time software requirement also means that if your PC running APE becomes very busy doing other things, you won't get SIO errors and timeouts, just slightly slower reading, like you would get with a regular floppy drive when it seeks between tracks.

Feature Set

The USB interface has been designed to implement all of the features normally available when using APE with a SIO2PC Universal adapter.

Additionally, the USB interface allows for a few new features, including:

As additional features become available, firmware updates will be issued.

Device Firmware

The firmware of your interface is field upgradeable. This allows new features to be added to your interface at any time, simply by downloading the latest firmware from this site.

As with all new hardware, there are likely to be a few bug-fixes for both APE and the USB interface firmware shortly after the initial release. If you experience any problems please send bug reports to

When these firmware updates are available, there will be a link on this page, as well as the main page, to the download location.

Once you have obtained the firmware upgrade file, you can apply it by opening the APE for Windows configuration manager and on the 'USB' tab select 'Install USB Firmware Upgrade'. An interactive dialog will then guide you through the update process.

All future firmware updates for this device will be free of charge.

Fully Self Powered Operation

Standard SIO2PC adapters draw power from the Atari SIO bus, or in some cases attempt to draw power from the RS232 port.

What little power the USB interface requires it draws directly from the USB bus.

This allows ProSystem to operate disk drives and other peripherals without an Atari computer attached to the SIO chain to provide extra power.

Software Support

As of the initial release, only the APE for Windows software, version 3.0.0 or higher, supports the USB interface.

Both the trial version and registered versions of APE support use of the USB interface, though some APE and ProSystem features may be unavailable in the trial edition.

As time allows, developer documentation will be posted to this space so other SIO2PC programs can be modified to support the interface.

I don't like to sell features or products that don't exist yet, so if you do not intend to use the APE for Windows software, it is highly recommended that you purchase or continue to use the Serial/RS232 Universal Adapter until 3rd party support documentation for the USB interface becomes available.


Should you encounter any problems with your USB interface it is recommended that you unplug the interface from the USB bus for five seconds, then plug it back in.

This will allow the on-board MCU to fully reset, clearing any error condition. You should then restart the APE software.

If possible, please report any bugs or problems with operation to

Still Awake?

To get started with your interface, lets move on to Chapter 1 - Software Installation


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