exxos's Atari, Amiga & retro forum

Good Morning,

OK, as promised, some details of the additions, coming from the ATX ST...

First: Keyboard/Mouse/Joystick Interfaced - there, basically the Eiffel Interface is used
The ATX ST used a stacked Mini-DIN6 port for Keyboard&Mouse. This is really hard to source these days, so I went for separate Mini-DIN6 ports
The two Joystick ports go to IDC-2x5-Headers and can be wired to the port area of the ATX, using standard IDC cables

The ATX ST did not use the part for connecting an LCD display and controlling a fan - this I have integrated again

LCD, pins connected 1:1 to the LCD
Fan, using standard NTC as temp sensor and using the +12V coming from the ATX power supply
both, LCD and Fan is completely optional

PCB-Layout

Mega ST Keyboard Connector

Since people might not like to use Eiffel (and PS/2 Keyboard&Mouse), I have added the required components to attach a Mega ST keyboard.
A jumper field can switch between Eiffel and the RJ12
The RJ12 (incl. power supply and the 3 caps) will be integrated on a separate "2nd layer PCB", which can be mounted on standoffs in the ATX port area (will be shown later)
selection is simple:
If Eiffel is used, two jumpers need to be in the upper positions (1/3 & 2/4)
If RJ12 is used, two jumpers are in the middle position (3/5 & 4/6) - then pins 7/8 are RX/TX for the RJ12


Cheers
Michael

I will continue right away with another two aspects:

• ISA slots for STGA and e.g. ROM-Port PCB

• ATX Power Supply

first to the ISA Slots...
The ATX ST included one ISA Slot for using an ET4000 based VGA graphics card, based on the STGA concept
The used GAL and the required drivers are from IDEK

Worked very well on the ATX ST (at least after correcting one layout issue on the ATX PCB)
Since the ATX ST did not contain the cartridge port, a separate ISA card was designed to offer the ROM-Port (scroll down to the end of the page).
First, I tried to add the cartridge port into my design - but no way, space is too tight on the micro ATX...
So, a second ISA Slot would be handy...
This I liked to have anyway, because then you could also add other extensions, like EtherNEC or NetUSBee

So I added a second slot to the ATX
The original design uses a transistor for the DACK signal.
In another forum it was reported, that this can cause issues and can be replaced by a HC03 (need to search for the reference...)
I integrated both options - only one shall be populated

since e.g. the Cartridge port needs ROM3/ROM4 signals, not present on the ISA slot, I placed a pin header close to the 2nd ISA slot, so we can wire them to the card.

BTW: I tried to read through documents describing the ISA interface, to figure out, if some of the signals can be re-used to wire ROM3/4, but I did not succeed.
I want to avoid, that plugging in a VGA card (or any other card) will cause damages, if ROM3/4 are connected to the wrong pins on the ISA-Slot

Maybe someone has a good idea?

What to do with the 2nd ISA-Slot, now?

Of course, the existing design of the Cartridge-PCB from chillichai.com can be used "as is"
Version 1.1 is sufficient, since the RTC is already on the ATX
But even version 1.2. or 1.3 ca be used, if the RTC will not be populated
Version 1.3 also adds a connector to a separate board to realize EtherNEC

speaking of EtherNEC, I am thinking of another option:
designing an ISA card to incorporate NetUSBee (this was already asked below) - the design is free and does not look that complicated
Would offer Ethernet and USB ports
Maybe this could be even integrated into the ROM-Port-PCB - not sure yet...

Cheers
Michael

now to the ATX power supply...

The design als includes a barrel jack for using a simple 5V power supply.
But this is mainly for testing.
If other devices (CD ROM, Hard disks, etc.) are equipped inside a ATX case, a real ATX power supply would be used
Esp. since some VGA cards require also -12V (besides +12V), and e.g. for a SCART Video cable, real +12V would be also good
BTW: for the serial connection, only 5V are required, since I am basing on the H5 design, using a MAX238

The ATX power supply provides all voltages required

One problem of the original ATX ST design was the design of the power-on of the ATX PS
There is a pin header, where you had to switch the PS-ON signal to GND - but most (all?) ATX cases have a momentary switch only
So I made some research and found a simple design, using an ATTNY84

The ATTINY is powered by 5VSB (standby) and:

• drives an LED to show if 5VSB is present (Pin5)

• reacts on a momentary switch, if Pin6 is pulled to GND

• and then pulls Pin10 to GND - which is connected to PS-ON of the ATX PS

• if the momentary switch is pushed again for more than 3 seconds, PS-ON is disconnected from GND again and the PS switches off

If a "real" switch is used for power-on, of course the ATTINY part can be omitted, and J30 can be used

Cheers
Michael

Mikerochip wrote: 22 Feb 2024 10:47 Hi!

I built the Angel_X micro ATX ST mobo, and something I found I dearly missed, once I had it built, was the ST High video signals.
(Missed as in, missing from the design ethos, not missing entirely. It works fine from the DIN13)

So, I bodged in the two missing signals to the RGB 2x8 riser, and I can only suggest you do the same.

One for Mono out, one for mono enable.

Having a "VGA" riser that can't actually use the ST native VGA signal is a bit of a pain :P

If nothing else, it will let you make a switch to enable ST high, without having to use the 13 pin DIN.
(Which would have been quite an easy addition, I think)

People might ask why have this, when you're probably going to make use of other video cards...
Because! It's like not having the cartridge port. It's not really a 100% compatible ST without it :D
(Or, that's my opinion, anyhow...)

If you're adding in the RJ11 connector for Mega/TT/MSTE Keyboard, why not add the 7 pin riser for the standard ST/Falcon keyboard too?
No reason other than to give the end user more options/flexibility!
It's really nice to be able to test a PS/2, ST, TT keyboard all from the one machine.

If you're adding an Eiffel, and the PIC, I have two suggestions: One, use the new firmware from the Polish atari forum, which solves the right mouse button/fire problem that was never addressed in the existing (final) firmware, and two, have an enable jumper, for the PIC 5v line?

It's nice to have the Eiffel, but, if you do want to switch/test another keyboard, you can't once the Eiffel PIC is actually installed.

Apologies, I did not answer to your suggestions…

Eiffel switch off - I prefer switching over the RX/Tx signals and leave the PIC running, to keep temp. sensor and fan

7p keyboard connector - attaching a internal ST keyboard would be a pure temporary/testing use-case… Do not see a real reason, but it is just a pin header… :-) if the signals are close, no big deal… need to check

Mono signal - the switching to Mono can be done by an accessible pin header. The signal itself is part of the H5 Mux and video DAC mimic, so the hi-res signal already reaches the VGA IDC port on the board

Regards
Michael

Hi,

Ordered the first prototype boards…

2nd level board for add. ports
Mainboard

Magnificent. Nice work.

Incredible. Looking forward to seeing the build log.

:bravo:

Very promising !

exxos wrote: 03 Mar 2024 22:46:bravo:

Thanks :D

Since it is the first prototype, I am quite satisfied
Although I am not that happy with the overall routing…

I have routed some crucial parts manually, then let the autorouter do its work, and then changed a lot manually again.

Depending on how much I have to change during troubleshooting, I am considering doing the routing again. Manually then…
Let’s see

BTW: for this first prototype, I decided to let JLCPCB only assemble the „small SMD stuff“
I am already having most of the 74 logic chips available (for hand soldering), but for the final run most of them can also be assembled by JLC

Regards
Michael