myne wrote on 2024-09-29, 09:08:

China and fraud.

Name a more iconic duo

Actually, the ones I bought from China were good... The ones from South El Monte, California were bad. Oh, well I guess.

Ah, will look at CMI8330. I have a few cards with the ES1869F and I'm routing things for that. Hopfully the samples I ordered will work and I need to build a test platform before I solder one onto a future backplane. 😅

Made some headway on the layout. Things are getting SUPER tight! Waiting for the sample ES1869F chips and the test fixture.

This is a list of features I wanted.

Wavetable header: This will have to be a backward vertical mount because of the lack of PCB space. This should allow the smaller wavetable cards to be mounted vertically behind the SBC but a short ribbon should also work for larger ones.
3.5mm audio jack onboard
AC97 compatible header
CD audio input
Joystick port
Optional EEPROM
Disable jumper

Still a ways off, but I believe this can be done!

Dump the post card. You have a real one anyway.

myne wrote on 2024-10-03, 11:50:

Dump the post card. You have a real one anyway.

What! The whole point was that I wouldn't have to use the POST card because it was built in! I spent a lot of time laying that out and I was happy that it worked.

I refuse!! 😋😋

Lol ok.
Could you squish it a bit? Maybe put a few chips on the back or in front of the pci slots?
Sound cards need low noise

myne wrote on 2024-10-03, 13:31:

Lol ok.
Could you squish it a bit? Maybe put a few chips on the back or in front of the pci slots?
Sound cards need low noise

Yes, I'm aware the sound card needs a quiet spot, but specifically the anolog signals need a quiet spot. The choice to put the chip on the bottom left seemed reasonable as it's reasonably isolated as no other signals pass through there. I was able to segregate the lower left for the analog ground section and there's is a ground split in that area that encompasses all the analog side of the chip. I also kept the anolog voltage source low near the ATX connector. This ensures a seperate physical location off axis to the main current flowing through there. Running the 3.3V under the right side of the chip was unavoidable. That's the vcore line for the Allen Bradley variant. I couldn't place in anywhere else without major rerouting of digital traces. The chip is close to the main processor on the SBC relatively speaking, but the perpendicular orientation should keep noise from the SBC to a minimum. This is all an assumption and testing is needed to validate that.

That spot was also reasonable for the numerous ISA bus pins. Having to route all those pins up and over the PCI slots would have been very difficult and the space on that side is smaller. And, I'd like to keep this on 6 layers...

I'm trying very hard to keep this a single sided board. Obviously, I could place components on the back side, but I want to avoid that if possible.

This is just a preliminary layout but I feel good about it.

How about moving the post card chips in front of the pci and leaving the displays where they are?

myne wrote on 2024-10-04, 01:28:

How about moving the post card chips in front of the pci and leaving the displays where they are?

Well... It's not impossible. I've been staring at this for a bit and I may need to scrape this layout. I might need about 10mm more space to add some proper coupling caps to the audio signal path which pushed things further right.

This was just a preliminary layout and I might try to move some of the logic chips to the top as you mentioned. It might not be that bad. 🤔

You did say the goal was for either card to work in either slot, so if you delete one, the space increases.

I'll be watching this closely, as I am rather a fan of SBCs, and have a number of PCISA/PISA boards.

- Alex

myne wrote on 2024-10-04, 12:48:

You did say the goal was for either card to work in either slot, so if you delete one, the space increases.

The two slots are for flexibility. Depending on what SBC and how wide it is, you can position things to fit better.

For instance, I had an arrangement that worked better with the SBC in slot 2 so an ISA card could go behind.

Also, with the three ISA compatible slots, you can use an ISA SBC with two available ISA slots.

ajacocks wrote on 2024-10-04, 15:02:

I'll be watching this closely, as I am rather a fan of SBCs, and have a number of PCISA/PISA boards.

- Alex

Ya! I'm excited to make this next version work. I know there's a few PCISA fans out there! 😋

But... There's only one isa slot...?

myne wrote on 2024-10-05, 01:23:

But... There's only one isa slot...?

The SBC slots are ISA compatible! It's a dual level edge connector. ISA pins on top with the same pin pitch, PCI pins on the bottom but need to be routed to the PCI slots. 😁

Crazy 😮

Okay, only a little hair-pulling, but I was able to "find" some board space for the ES1869F! 😅

I moved all the POST logic to the top. While the flip-flop was involved in showing system activity on the 7-seg decimals, I've chosen not to include that. This way the chip that has the flip-flops can stay near the ATX connector where it's being used. This gave enough space for the sound chip while still observing the space required for the SBC overhang. In this version, I removed all the tantalums in favor of the poly-hybrid cans and ceramics. I also reduced the number by a few by including some larger value 10mm cans.

I was able to include all the features I wanted so that's nice. I'm still planning to build a test fixture for the chips but I haven't started that yet.

If everything looks good, this will be V0.4.

I included a stand-in for an SBC with similar dimensions to one I have. You can see how pronounced the overhang is here. It's not impossible that I could have used a flat mount 3.5mm jack, but this vertically mounting one has a nicely small footprint. Depending on the requirements, the AC97 header can also be used. The wavetable header also had to be mounted vertically. This makes it possible to mount a small wavetable card upside down on the rear of the backplane. It looks precarious, but there just isn't room anywhere else and I didn't want the card to hang off the backside. Either way, a short ribbon can be used.

Would the wave table fit next to the cmos battery without overhanging if you swap that header?
I just figure not all boards are going to be as short

Technically yes but only if I move the mounting hole on that side, or make the board longer. Neither of which I want to do.
The mounting holes were a decision for practicality. The holes on that side align with the ATX mount for a full-sized motherboard in case someone wants to mount this in something else other than a custom-made enclosure.

The vertical upside-down mount should be fine for most or all of the small wavetable cards out there. It should be okay tucked away on the rear of the backplane when mounted inside an enclosure.🤞

Received the sample ESS sound chips and ZIF socket finally. Still working on a super simple ISA mockup so I can test the individual chips before soldering but I should be ordering the boards soon. 🎧🤘🤘

Nice project, it it possible to purchase board? 😉