New project: ATX motherboard for the Atari ST

[czietz]

Hm, I wonder if putting 5 V on pin 6 (transistor base terminal) of the 4N33 would already be enough to release the magic smoke...

The optocouplers used by Atari on the MIDI port (H11L3 or Sharp PC900) are quite fast and they have a built-in Schmitt trigger to ensure proper logic levels. (... which is why they need 5 V supply.) The 4N33 has neither of these features.

[DoG]

Aah. Yes, sorry. Don't put 5V on the 4N33.

[kodak80]

I agree that the mATX schematic looks correct and that pins 4 and 5 are correct but MIDI in does not seem to work in my testing. I am not sure that using the 4N33 is a good choice for MIDI as it may not be fast enough?

[umatthe]

Did You try to use a lower pullup resistor? In case You still have the 4k7 in place just solder a 1k parallel to it.

[kodak80]

Did You try to use a lower pullup resistor? In case You still have the 4k7 in place just solder a 1k parallel to it.

Will try this and let you know.

[kodak80]

Okay, I have the mATX ST MIDI in working now with original pinout. Using an alternate optocoupler CNY17F-3 chip borrowed from one of my H4 boards.

CNY17F-3 Optocoupler.jpg

MIDImaze 2 connects and works

[higashijun]

Okay, I have the mATX ST MIDI in working now with original pinout. Using an alternate optocoupler CNY17F-3 chip borrowed from one of my H4 boards.


CNY17F-3 Optocoupler.jpg


MIDImaze 2 connects and works

[RealLarry]

Okay, I have the mATX ST MIDI in working now with original pinout. Using an alternate optocoupler CNY17F-3 chip borrowed from one of my H4 boards.

MIDImaze 2 connects and works

Thanks for confirming this!

[Atari030]

MIDImaze 2 connects and works

Can't claim to be Atari compatible if it won't run Midi maze.

[swatcop]

Apologies if this isn't proper to post here, but I simply have to get one of these boards and will pay to get one - preferably two. I also understand that these will be expensive as there is a lot of time and labor involved. If any of the true hardware experts here would consider building a couple tested/fully functional boards, I'm all-in, please contact me.

If there are no takers, as someone who has never ordered a PCB how would I go about having PCBWay or JLCPCB populate the SMD components (correctly) and possibly even some of or all of the through-hole sockets/parts?

I've done a lot of successful through hole soldering but noting of this scale. Uploaded the Gerbers to the aforementioned companies, but can't figure out how to get the BOM (.CSV file) uploaded. I just don't want to spend a bunch of money only to receive something I don't have the skills to diagnose/correct if I screw up in the ordering process.

[Mikerochip]

Hey swatcop,
If you're using the bom from here, you'll need to create a Bom/csv yourself instead,
the one provided here is only, I think, an export from Eagle, and is a rough guide to what you need to order.
There's steps on JLCPCB on how to create and upload a BOM, btw.

I can help out, if you get really stuck, but, if you want me to solder, the price would be awful, since I'm in Ireland, and you're ... not.
But, if you want to have a go at making it yourself, I can give you a few pointers and such.

[swatcop]

Hey swatcop,
If you're using the bom from here, you'll need to create a Bom/csv yourself instead,
the one provided here is only, I think, an export from Eagle, and is a rough guide to what you need to order.
There's steps on JLCPCB on how to create and upload a BOM, btw.

I can help out, if you get really stuck, but, if you want me to solder, the price would be awful, since I'm in Ireland, and you're ... not.
But, if you want to have a go at making it yourself, I can give you a few pointers and such.

Thanks for the reply @Mikerochip
I saw the site says you can upload a BOM but I couldn’t figure out how where to do it on either of those PCB websites. I downloaded a .CSV from http://ataripcb.pl/atari_st_atx_v1.1.html which looks like a text file with the resistors, caps etc. but I couldn’t figure out how to add it when I uploaded the PCB file. If OK, I’ll IM you so as not to muddy up this thread.

[DoG]

I saw the site says you can upload a BOM but I couldn’t figure out how where to do it on either of those PCB websites. I downloaded a .CSV from http://ataripcb.pl/atari_st_atx_v1.1.html which looks like a text file with the resistors, caps etc. but I couldn’t figure out how to add it when I uploaded the PCB file. If OK, I’ll IM you so as not to muddy up this thread.

The bom is not enough if you want the factory to solder the smd for you. You also need a file with the coordinates and rotation of each components for the pick-n-place machine.

[Oldskool]

SMD soldering is easier than you think. Just order the pcb and try it maybe watch some YouTube first. Get some good SMD tweasers and some flux. If you can do through hole you can do this. Start with the smallest.
You can do it. You can’t really mess it up. Just go one by one.
After the first 10 pieces you will be an expert.
If I can do it you can do it.

[Mikerochip]

Howdy all. Anyone know where I can find the floppy drive led, for the keyboard??

Looking at the STE schematic from sporniket, it looks like it's from 74LS244 (HI) Pin 18 (BD0SEL). Correct?

I've had a bunch more hassle with the PIC, including but not limited to it not working in certain games!
(It stopped working 2-3 more times. Usually after something traumatic! Like, when I accidentally dropped the case... Because I'm an idiot)

So, I'm just going to patch in a real keyb.

I've figured out where I'm putting most of the pins, but, not that one.

Code: Select all

8 Pin Keyboard
PIN		Connection		mATX				
===============================================
1		GND			GND
2		NOT CONNECTED		N/C
3		Floppy Light		???					
4		+5v			+5v (C32)/(C34)
5		RX Data			IC1 Pin 2	(6850)		
6		TX Data			IC1 Pin 6	(6850)			
7		RESET			IC7 Pin 23 (Yamaha) / IC15 Pin 2
8		GND

or for the Mega ST/STE/TT keyboards:

Code: Select all

6 Pin RJ11
PIN		Connection		mATX				
===============================================
1		+5v			+5v (C32)/(C34)					
2		+5v			+5v (C32)/(C34)
3		TX Data			IC1 Pin 6			
4		RX Data			IC1 Pin 2			
5		GND
6		GND

I know I can pull the pins from the PIC socket/area, too.

How do the Mega keyboards reset, btw?
The internal ones reset when the processor asserts the reset pin, but, do the external keyboards do it differently?

[DoG]

... Anyone know where I can find the floppy drive led, for the keyboard??...

IC20, pin 12 on mATX.

...How do the Mega keyboards reset, btw?
The internal ones reset when the processor asserts the reset pin, but, do the external keyboards do it differently?...

It has it's own reset circuit.

[Mikerochip]

... Anyone know where I can find the floppy drive led, for the keyboard??...

IC20, pin 12 on mATX.

Outstanding! Thanks!

...How do the Mega keyboards reset, btw?
The internal ones reset when the processor asserts the reset pin, but, do the external keyboards do it differently?...

It has it's own reset circuit.

I figured it had it's own, sorry, I wasn't clear. How does the keyboard know a reset has been asserted on the ST?
Is there a reset command sent to the ikbd, over serial?

[kodak80]

Howdy all. Anyone know where I can find the floppy drive led, for the keyboard??

Looking at the STE schematic from sporniket, it looks like it's from 74LS244 (HI) Pin 18 (BD0SEL). Correct?

I've had a bunch more hassle with the PIC, including but not limited to it not working in certain games!
(It stopped working 2-3 more times. Usually after something traumatic! Like, when I accidentally dropped the case... Because I'm an idiot)

So, I'm just going to patch in a real keyb.

I've figured out where I'm putting most of the pins, but, not that one.

Code: Select all

8 Pin Keyboard
PIN		Connection		mATX				
===============================================
1		GND			GND
2		NOT CONNECTED		N/C
3		Floppy Light		???					
4		+5v			+5v (C32)/(C34)
5		RX Data			IC1 Pin 2	(6850)		
6		TX Data			IC2 Pin 6	(6850)			
7		RESET			IC7 Pin 23 (Yamaha) / IC15 Pin 2
8		GND

or for the Mega ST/STE/TT keyboards:

Code: Select all

6 Pin RJ11
PIN		Connection		mATX				
===============================================
1		+5v			+5v (C32)/(C34)					
2		+5v			+5v (C32)/(C34)
3		TX Data			IC2 Pin 6			
4		RX Data			IC1 Pin 2			
5		GND
6		GND

I know I can pull the pins from the PIC socket/area, too.

How do the Mega keyboards reset, btw?
The internal ones reset when the processor asserts the reset pin, but, do the external keyboards do it differently?

Just to check, you have TX Data on IC2 pin 6 but this should be IC1 pin 6 on the mATX board?

[Mikerochip]

Sorry, yes, both on ic1

[Arne]

How does the keyboard know a reset has been asserted on the ST?

PowerOn Reset circuitry.

Is there a reset command sent to the ikbd, over serial?

LOL - that would be pointless! Think about it: what can a Reset command achieve if the IKBD's SW hangs up?

[Mikerochip]

So, looking at this more ...

The only thing I'd *really* like to add, then, that Kodak80 hasn't made a PCB for is a blitter!

Looking at the Mega ST schematics (I can't find decent/clear ST(F)(M) ones), most of the signals on the blitter are on the 68000/bus too.

Apart from the Blitter;
Pin 41, INT, which goes to BLT INT, which goes to 68901, pin 25, with a 4k7 resistor pullup,
Pin 37, BGO, which goes to the (unconnected) pin 45 on the Glue,
Pin 40, BGKI, which goes to BGK, Pin 41 on the glue, with a 4k7 resistor pullup.

(Both resistors are already in place, it looks like)

Does that sound right?

Do I need to do anything to enable the blitter??

[Mikerochip]

OK!

Some mistakes were made

So, I had to cut two traces, and use two bodge wires (and two 4k7 pullups on the back) to fix.

But, blitter PCB is working fine, as far as I can see.

One wire needs to connect from the pin header, to 68901 (pin 25) and that's it.

20230702_114702.jpg

[shoggoth]

Beauty!

[Mikerochip]

It'd look a bit better ... without the bodge wires But, I made some assumptions, and uh, was wrong! Anyhow... All good now

I left it running on the Blitter Demo from Exxos forum, for over an hr, and it was fine, so, I reckon I'm good.

[higashijun]

Nice !