Different types of SIO2PC hardware

[morelenmir]

It is very easy to make an SIO2PC-USB device using an FT232R chip from FTDI. Mine was based on a breakout board for that chip which in turn was made by 'Sparkfun'. However. while participating in another thread today it was brought to my notice there are actually several different devices that do the same job which also work with RespeQt.

 

Previously I had believed all the commercial devices were just variations on implementation of the FTDI IC. Apparently this is not the case and the AtariMax SIO2PC at least uses a custom programmed microcontroller to more quickly handle communication from the Atari to the emulated drives it mimicks. Are there any others? More to the point, are there any other SIO2PC designs that are open and possible to build for oneself?

[+Larry]

Several -- for the RS232 port. And those were based either on the Max-232 or 1489 (or the better 14C89). A few even used other IC's, but these two were the most common. The "father" of SIO2PC was Nick Kennedy who started things with the Max-232. Rick Cortes (IIRC) simplified things with the 1489. If you Google Nick Kennedy, you should find his site and lots of info. Before Steve Tucker did the SIO2PC-USB adapter, he also had plans at his site for building the 1489 version. He had a really clear diagram for builders.

[_The Doctor__]

actually go further back to the 'Critical Connection' devices... and then you will be closer to the start of this.....

[+Larry]

Yes, I had forgotten about the Critical Connection for CPM systems. I did find the users manual by Googling "Critical Connection" CPM Computers

 

If you type much else, you get a bunch of references to the "Critical Path Method."

 

Do you have any info on the cable construction? Since it was also a serial port device, it must have been fairly similar.

[_The Doctor__]

it was rs232 to sio, required a power adapter, and was pretty darn fast, and it used atr images long before the others as well.... before the atr was re invented it would seem.

it also allowed the cpm machine to act as the Atari's keyboard...

 

the device itself is encapsulated in blue expoxy

[+Larry]

"the device itself is encapsulated in blue expoxy"

 

I wonder if Bob Puff made them for him?

[_The Doctor__]

lol gotta love 1979 blue epoxy, looks like a blue brick... the sharp edge all around the top wasn't ground off, still pretty painful after all these years....

[morelenmir]

Many thanks for these suggestions guys!

 

From what I have read the AtariMax device is an absolutely excellent piece of work and highly recommended. Sadly its a bit pricey for my pocket at the moment when combined with the APE client software--especially after HM Customs and Excise extract their iniquitous pound of flesh from the equation as well! Therefore I may have a go at putting together one of these other models.

 

So far as it goes the bare FTDI-based device works really well and I think everyone should have a try at assembling one. It is a very cool little project and gives you a real sense of achievement when you hear that POKEY 0 traffic rattling along like an Avenger cannon! However the potential to maybe handle some of the SIO devices more accurately--particularly the DOSXE/XF551 combination--has got me very interested in trying out another approach.

 

If I meet with any success I will post my results here.

 

This seems to be a very handy page with lots of info:

 

http://ftp.pigwa.net/stuff/collections/atari_forever/Extension/Sio2PC/The%20SIO2PC%20interface.htm

Edited August 23, 2018 by morelenmir

[morelenmir]

For all the original SIO2PC and its COM/DB9 interface is old I think it has some positive points over USB and I have bought a cheap PCIE card that adds two COM ports to my motherboard.

 

To me one of the old format's key positives is the robustness. The first SIO2PC-USB I built with a sparkfun board had to be thrown away because the mini USB socket physically broke off the breakout board! I have heard that this is not a unique experience either! Also it is far easier to fit the electronics in a project case and connect the PC->SIO2PC through a totally standard COM cable, which is attached solidly at both ends by screws instead of modifying a USB cable to be more resistant to sheer stress. The SIO2USB->Atari side has to be customised to some degree however. Either a DB9 plug needs to be added to a cut up SIO cable or a DB9 socket attached to the Atari case and then patched in to the SIO circuitry. Again given the cheapness, strength and availability of COM cables over even reproduction SIO cables I think I will follow the latter route.

 

Another very encouraging aspect is that it seems much easier to programme for a real COM port than it is to use the virtual COM port which an RTL232 emulates. I find this attractive as I think I would like to experiment with implementing my own PC-side software client. Certainly it will be interesting to see if RespeQT performs any differently if it is connected to the Atari via this route instead of an SIO2PC-USB. I also think it may be much easier to investigate the possibility of emulation of the Atari drives using a PIC or AVR in complement to the base hardware if the underlying platform is a simple SIO2PC.

 

These are all just preliminary ideas however and I look forward to playing with the design a little.