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TheMontezuma

DIY 4xOS Switch

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A few years ago I searched for an OS switch solution to support alternative OS versions for the SIO2BT project

and I found the following web page created by Igor Gramblička:

http://blog.3b2.sk/igi/post/Vymena-ATARI-OS-1_2-Change-ATARI-OS-1_2.aspx

One can use a stripboard or even bend the EPROM pins (which I did) to achieve the goal.

 

Recently I asked Mr Robot for designing the board with KiCad and he kindly agreed.

With his permission I would like to share his magnificent results here:

 

post-29824-0-98368500-1547721632.png

post-29824-0-26403300-1547721767.png

post-29824-0-19392000-1547721785.png

 

The Gerber files:

4XOS.zip

 

For a few dollars you can order a set of ~10 boards at:

http://dirtypcbs.com/store/pcbs

 

You just need two 4k7 resistors, PIN headers, IC socket, 27C512 EPROM and external switch(es) to build your own OS switch.

 

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Very nice and compact. Maybe it could be slightly improved by having the top socket offset to the other side of the underside headers, to allow more room if next to a similar adapter in the BASIC socket on an 800XL?

 

I tried this recently, and got dropcheck's 4-in-1 OS adapter to fit next to the RetroInnovations 2364 up-to-8-in-1 adapter, but only by using an extra socket to offset the height of PCB's: http://atariage.com/forums/topic/284992-does-atarimax-take-paypal-a-fork-of-the-old-steve-takes-ages-to-reply/?p=4164363

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Good point, here's a new version with the pins moved over and the board trimmed along that edge as close as it can be.

 

post-62759-0-24842200-1547762516.jpg

4XOS.zip

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I have a circuit (heretofore untested) that uses three pull-down resistors and two NOR gates from a 74LS02 TTL chip that will allow the use of a single pole 4-way switch (rotary or slide switch) for OS selection instead of the 2-bit binary switching. It uses a 4 to 2 encoder circuit with NOR gates. Position #1 is open (NC) because the three inputs on the encoder are pulled down. As a result, in position #1 pins A15/A14 on the eprom are set High/High. When switching to positions 2, 3 or 4, either A15/A14 are High/Low, Low/High or Low/Low.

 

I need to acquire an eprom programmer or at least the temporary use of one, before I can build the circuit and test it but I'm over 99% certain that it will work as designed.

 

I think it might be possible to nest the 74LS02 inside the socket area of the board above or one similar, along with the three resistors for the 4 to 2 encoder. No pull-up or pull-down resistors are needed for the eprom pins because the 74LS02 provides the distinct logic states needed by the pins.

 

Has anyone else considered something similar to eliminate the need for the pair of binary selector switches?

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I was trying to figure this out as well, how to use a simple 4-position slider switch to choose between the four. This was for Dropchecks version, which had 3 pins for each switch, which has a seemingly unnecessary 'NC' pin... Also, when wiring to the switch, only one GND lead is needed.. so only 3 wires total running from the switch to the adapter are really required.

 

I came up with one drawing based on a 2-pole, 4 position switch that has two 'inputs' on one end, and another variation that put the 'inputs' in the middle...

 

post-53052-0-26565100-1556424836.png

 

This one has the 'input' in the middle, but depending on the switch, it may be at one end.

 

post-53052-0-71977400-1556425406.png

 

Some pics of an implemented version, but with 2 GND wires to the switch. (Could have just used 1, and bridged to the other side, for 3 wires total to the ROM adapter)

 

post-53052-0-45710300-1556425234_thumb.jpg post-53052-0-85688300-1556425247_thumb.jpg

 

Another variation is a 4 position slider switch that has a BCD style coding, i found a description of the switch wiring here:

 

https://forum.arduino.cc/index.php?topic=398157.0

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Using the NOR gates (or OR gates) will eliminate the need for the second pole on the switch, simplifying the wiring to the switch considerably. The OR and NOR will be inverted results (1234 vs 4321),

 

  • One of the inputs of each OR or NOR gate will be connected together and connected to position #4.
  • The other input for each OR or NOR gate will go to either position #3 or #2 respectively.
  • Position #1 is "NC"
  • The leads to #2, #3 and #4 switch positions should be pulled DOWN via suitable value of resistors (3.3K, 4.7K, etc)
  • Output of one OR or NOR gate goes to A15 and the output of the other one goes to A14.

This means with four wires to the switch (three inputs and one +5v), one can switch between four separate OS's.

 

Edit: I forgot to mention that in my circuit design, the other four inputs for the other two gates are tied to ground so they aren't floating.

Edited by Waynetho
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Upon reflection, I see that the DP4T switch option gives a more streamlined approach than my 74LS02 solution. The DP4T chip method only requires three wires and two pull-down resistors and no additional circuitry (74LS02). The NOR or OR gate solution makes the switch more logical in it's hookup but it requires more components to make it work.

 

Additionally, it will work with the board that is already in this thread rather than creating a new board with the logic circuitry.

 

I bow to a more elegant design. ;-)

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Interesting side story about a conversation I had with Wes Newell in the mid '80's regarding my plans to make a triple OS board similar to his Ramrod XL. He told me it would be impossible to make a 3-OS board unless I could source the special three position switch (ON-ON-ON) that he used with his board.

 

I proved him wrong. I used a PULL-UP resistor for the CS pins on the first and third chips, and a PULL-DOWN resistor for the CS on the middle chip. I used a DPDT "Center-OFF" switch to GROUND either #1 or #3 chip's CS in their respective switch position, along with pulling the middle chip's CS "HIGH" when in either "ON" position. In the CENTER-OFF position, the board defaulted to the #2 chip active due to #1 and #3 being pulled HIGH and the #2 chip being pulled LOW by resistors. The switch used five wires (CS-1, CS-3, GND, and CS-2, +5V).

 

This was accomplished with a switch readily available from Radio Shack. For the record, I didn't mass-produce the board or even give it a name. I made one for my 800XL and I believe two more for friends, all hand-wired.

 

I wish we had 27512 chips and the mod discussed in this thread back then as the OS daughter board required three separate 16k OS chips.

Edited by Waynetho
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I've got a 16 in one OS in one of my XLs. One EPROM, a hex encoded thumbwheel switch, wire and a few resistors. No board needed (although I should have built one for it). Those SCSI select switches work great for an 8 in 1!

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@JR> i like the sound of that setup?

 

what parts are required?

any pics?

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Pretty simple really, 27c020 EPROM, 4 pull up resistors for the additional address lines. The 4 encoded lines from the switch to toggle the 4 address lines. Pin compatible with the 27c128, so it just plugs in the OS socket with the extra pins hanging over the end, and one or 2 of the pins not going in the socket. Tap ground and +5v somewhere and wire it all up. I think I plugged the pins that didn't go in the original socket into some SIP socket and soldered to that.

 

I'll try to dig it out and get some pictures soon.

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Hi,

 

What other Atari OSes that one can put on with this board? Would appreciate links or even download links. I would like to try out this new OSes and see what they are/how they function.

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Hi,

 

What other Atari OSes that one can put on with this board? Would appreciate links or even download links. I would like to try out this new OSes and see what they are/how they function.

 

 

Saw the below at https://www.atariarchives.org/mapping/appendix12.php

 

"Probably the most elegant solution is the XL BOSS board which allows you to switch in a RAM OS, the older 800 OS, and the XL OS,

as well as turn BASIC on or off with a few keypresses. It's available from Allen MacroWare in Redondo Beach, California.

"

Edited by unebonnevie

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On 5/4/2019 at 8:54 AM, unebonnevie said:

Saw the below at https://www.atariarchives.org/mapping/appendix12.php

 

"Probably the most elegant solution is the XL BOSS board which allows you to switch in a RAM OS, the older 800 OS, and the XL OS,

as well as turn BASIC on or off with a few keypresses. It's available from Allen MacroWare in Redondo Beach, California."

I used this OS a lot back in the day, but as a kid I used it primarily used it for 800 compatibility for games, and was oblivious to many of its extra features until recently, and that there was a also "XL/XE BOSS II". ROM images, software and documentation are in this topic:

 

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So I ordered some of these OS switchers along with my 6810 doubler PCB's from OSH Park, and I am happy to report that in an 800XL it fits perfectly beside Go4Retro's 2364 adapter for BASIC. So this is a nice, simple solderless multiple OS & single/multiple BASIC replacement option  - even if only to upgrade do Atari BASIC Rev C next to it using a common EPROM as well.

 

Thanks @TheMontezuma & @Mr Robot for designing this. :thumbsup:

 

Minor operational observation... I noticed "SW2" toggles the OS on a 2xOS ROM, suggesting SW2 is A14, and SW1 is A15. Maybe the labelling of SW1/SW2 should be reversed, and/or named A15/A14?

 

I made up 1 of them fully to try, but ran out of pin headers to finish the rest, so they will be completed eventually. :) Some extras will be up for grabs, if others are interested.

 

IMG_9365.thumb.jpg.c8272eda6b00c9e0124de97114329d54.jpgIMG_9381.thumb.jpg.1885abbce9603d0223a6350107d21beb.jpgIMG_9382.thumb.jpg.d512ef920e1d2f4203a5271dbc0756bd.jpgIMG_9388.thumb.jpg.953e551f45ccf01133cab06702af60fb.jpg

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Hi Nezgar,

This is really cool, I am really interested, an planning to get more eproms to try all those OSs.

Only problem I saw when I tried to implement an OS switcher was that I got overwhelmed by the number of options regarding rotary switches (with encoding, numbers of poles, right angle, etc).  It could be any switch, but I think rotary switches are more elegant , like os 1 ,2 ,3 or 4 instead of dealing with all the combinations.

So the question is really to anyone: which rotary switch is good to connect directly to those 4 points (or maybe 3 points since gnd is repeated), and just work? Hopefully something small that can be glued and maybe reuse the rca modulator hole, of some vent hole, or maybe be accessed easily with a screwdriver after opening the cartridge doors, or any other idea that does NOT require a big mod to the Atari computer case.

 

Edited by manterola

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Yes, technically only 3 wires to such a switch should be necessary, since two of the pins should be the same...

 

Here is what the 4 position slider switch as seen in post #5 above can look like on the outside when all said & done:

 

1363939519_4positionsliderswitch.thumb.jpg.ea301d82ecfb63d0216ca1b3a37e557f.jpg

 

Two of these could be installed beside each other to select between 4xOS, and 4xBASIC if you do that as well.

 

However, I've been trying to find a current source for these switches. None on the likes of eBay/Aliexpress, and I'm not the best at drilling down on sites the likes of DigiKey/Mouser... 2 and 3 position slider and toggle switches are plentiful. I'm also curious about 4 position rotary switch recommendations. In theory the wiring would be similar to that of a 4 position slider, but it's hard to gauge the size of them from online photos...

 

If you only want to choose between 2 OS's with no external modifications, I found you can use the channel select switch for double-duty by soldering a single connection to the leftmost lead of the RF Modulator. If anyone thinks this electronically bad for whatever reason, I'm all ears. The OS ROM adapter and BASIC ROM adapters both use pulldown resistors, which should provide protection to the ROM chip from any stray signals...

IMG_9415.thumb.jpg.6dafbebf669ad28c8bd13482fd2990cc.jpg

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5 hours ago, Nezgar said:

I'm also curious about 4 position rotary switch recommendations. In theory the wiring would be similar to that of a 4 position slider, but it's hard to gauge the size of them from online photos...

The DP4T rotary switch below looks small from the images, unable to confirm but think the pin spacing is likely 0.1". It's the only one I can find at a reasonable price that's easy to mount.

https://www.ebay.ca/itm/2PC-10mm-DP4T-Rotary-Switch-Double-4-Position-15mm-Knurled-Shaft-PC-Mount-Switch/111989402572?hash=item1a1316abcc:g:SaEAAOSw9etXQYf-

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@BillC Nice find. Seeing 2 rows of 5 leads on it, those look they could re-use the same wiring as the 4 position slider shown earlier too... Are these generally all a standard 6mm shaft size? lots of knob options for 6mm... Still leaning towards the 4pos slider as the most unobtrusive though, especially if installing 2 for OS & BASIC... How's your luck finding those? :)

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12 minutes ago, Nezgar said:

Still leaning towards the 4pos slider as the most unobtrusive though, especially if installing 2 for OS & BASIC... How's your luck finding those?

DP4T slide switches aren't hard to find, but ones that are easy to mount are. Most of the smaller switches are designed to be PCB mounted.

The CW Industries G-141S-3011 available from Digikey & Mouser is the best I found so far:

https://www.digikey.com/product-detail/en/cw-industries/G-141S-3011/SW120-ND/9610

https://www.mouser.com/productdetail/cw-industries/g-141s-3011?qs=GMJVKvQynaBA71ZAi8xiaw%3D%3D

 

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This is older thread but would like to know if anyone is building this to switch OS?  I would like to implement modified OS to enable HSIO.  Thanks!

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 I have question, which of the wires are ground.  I ask because I am getting 4-way slide switch and need to locate them since I only need one.  

 

image.thumb.png.245f06acc120fa79c7b4fd02ae94cade.png

 

 

On the picture I have included I have numbered the leads.  Can you let me know which two are ground?

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