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creating a USB2SIO cable and installing Respeqt



Creating a SIO2PC cable for the Atari 8-bits with RespeQt is one of the cheapest and easiest ways to get virtual drives for the Atari and also one of the best. He's a little how to on creating the cable and getting RespeQt up and running.

Not to long ago I built an S-Drive for the Atari (see this blog). Also a fairly cheap and good virtual drive solution. It's portable and easy to use. But it does have one drawback, for me anyway. I do a lot of my development on my PC using Altirra and cross-compilers. So if I want to test a file on real-iron I have to pull the SD card from the S-drive, upload the file from the PC to the SD-card, remove the SD-card from the PC then put it back in the S-drive, fire up the Atari and load in the file to the Atari. A bit cumbersome procedure because of how fiddly it is to pull and re-insert that SD card in my S-drive. But with the SIO2PC and the RespeQt I can leave the Atari attached to the PC and just run the file straight on the Atari, no fiddling with cards.

What you will need.

You will need an SIO2PC cable and a copy of RespeQt. If you are running RespeQt on Windows you will also need a USB driver.

There are several ways to create a SIO2PC cable. I chose the one recommended in the RespeQt documentation. A 'FTDI USB to Serial Adapter TTL Cable 5V 6 Pin UART Female Header Converter FT232' pictured here:


I got my USB cable from eBay for $16 shipped. Lots of other places also carries the same or similar cable for about that price.

You will also need some way to attach the USB cable to the Atari. I got an SIO plug head at vintagecomputercenter for $6+shipping.


Any old SIO cable could work as well but I didn't have an old SIO cable at the time. 


Assembling the SIO2PC cable.

First off 'The modern Atari 8-bit computer' does an excellent tutorial on creating a cable and setting up the RespeQt software.

Watch Here. I would watch this first then but come back to this blog as he does skim over some important details.

Back, good.


Now when I got my USB cable it turned out that the colors of the wires weren't the colors listed by 'modern Atari' or in the RespeQt documentation. Bummer. So I had to do a little more research and create me a chart that could be used with my wire colors on my USB.

Here's what I made:

SIO  (pin)              my USB cable      type

green (5)               (yellow)                 RXD

black  (4)               (black)                  GND

orange (3)             (orange)                TXD


looking from the back of the connector


You only need to connect three lines from the SIO to the USB; RXD, TXD and Ground. The color chart above was from a SIO2MIDI project someone once posted. The colors on the SIO 'should' always be the same. On the USB, maybe. Check your documentation that comes with your USB for it's color to signal type.


I cut the head off the USB cable then tested fitted the USB cable to the SIO plugs and inserted them into the SIO head unit.




Then I tested plugging in the SIO head into the Atari.


Fit was good. Now on to the software.


Setting up the RespeQt sofware

If you are using RespeQt on a Windows 7-11 machine you will need a driver: CDM21228_Setup.zip 

Run the setup software for the driver on your PC before installing the RespeQt software. This will create the virtual COM port you that will need for RespeQqt. At this point you can attach the SIO2PC into a USB port on your PC. It 'should' find the right driver and create a virtual COM port on your PC.

Now the RespeQt software. get it here: https://github.com/RespeQt/RespeQt

Be sure you download the latest release and READ the bug list. v5.3 has a bug that will brick 'THE CART!' if you try flashing a copy to it.

There are multiple packages for multiple PCs. I downloaded the Win64 package and it came with all kinds of goodies.

In the package was the RespeQt software and all the .dlls needed, three ATASCII fonts for Windows (load them), a manual, how to create a USB2PC cable, how to compile the program and several Atari 8-bit programs, of which, I so far haven't needed (you might so check them out).

To run the RespeQt software you will only need to copy the RespeQt directory from the .ZIP onto someplace on your PC. To execute the RespeQt software just click on the RespeQt.exe. This will start the setup routine for the software. For the FTDI USB pick the virtual COM port the driver software created. Then chose HANDSHAKE method of 'Software(SIO2BT)'. I found this handshake method the most stable but you can also choose NONE which is a bit faster but can be a bit unstable at times.

The setup screen:


The handshake of SOFTWARE(SIO2BT) loads the Atari software at about standard Atari drive speeds. Not fast, but also not too slow. I tested some high speed SIO routines but none seemed to work. If you set the handshake to NONE the high speed routines do work but under certain situations I had trouble loading.

Note: printing doesn't currently work in Windows version. Try to print will usually result in crashing the program. The programmer is aware of this issue and is working on a fix.

After you have tested the cable and the software you can now close up and solder the SIO plug head.


Note the little bit of tape I used around the cable so the shell would clamp the wire tightly. The only real problem I had with the shell is the supplied screw was too short. I got another screw and it worked fine.



RespeQt has a lot of capabilities to it. I can run .ATR files, it can load from PC directories, it can be set to boot OSB automatically and bunch more. I managed to load almost all of my files except 'Music Construction Set' which is my only .ATX file. .ATX support is still under development. A side project from another set of programmers, which may or may not come to fruition, is including an N: network device. Would be nice.

That's it, cheap and very useful, the RespeQT with an SIO2PC.










Recommended Comments

Even though I have an awesome AtariMax SIO2PC-USB dual port interface, I made one of these a couple of years ago as well. I had a bad SIO cable and the bad wires were towards one end, so I just cut off the cable and had most of the SIO cable left, as well as most of a 6' FTDI cable, so I have an approximately 8.5' SIO2USB cable. It was a relatively easy project, but fun, and it works great. I had to look through several sites and compile the information that I needed. Your blog post would've been really helpful. Hopefully, it will help someone else interested in doing the same in the future.


Now that I'm planning to purchase a FujiNet, I doubt this cable or my AtariMax interface will get much use, but I don't regret either of them. They're both awesome tools.


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Maybe you can connect other 2 PINs of your FTDI based adapter, COMMAND and PROCEED. Then you can use hi-speed SIO and you can play with FujiNet too 🙂


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