Pokeymax v4 bring up thread

[madness77]

16 minutes ago, ScreamingAtTheRadio said:

JLC came back to me with a concern that the discrete footprints on the PCB are not really 0402 like the footprint name would suggest. I'll have to replace the components I selected. This is a very minor setback but out of curiosity, @foft can you confirm what the intended footprint was for those?

I also had a similar question, but it concerned CN1:

 

[woj]

foft certainly noted that the inductor footprint seems oddly small. I for one suspected that the RNs footprint is not ideal due to problems with them sticking properly when soldering, and I was not the only one having issues there.

[ScreamingAtTheRadio]

2 hours ago, woj said:

foft certainly noted that the inductor footprint seems oddly small. I for one suspected that the RNs footprint is not ideal due to problems with them sticking properly when soldering, and I was not the only one having issues there.

Yeah, the networks are all gone from what I sent in: there's enough space in there to replace with discrete versions for those that are actually used. The ones that seem to not be 0402 are the existing discrete caps and resistors, like those on the periphery of the board. 0402 is really small, and the footprints look more like 0603. Not sure yet, will check tonight.

[foft]

Yeah the pads did seem pretty big when soldering parts on. Eagle definitely shows 0402 on the bom. Did I do some weird imperial/metric screwup or something?

 

They don’t look that large, just a bit more than necessary: 

 

Edited August 22 by foft

[ScreamingAtTheRadio]

7 hours ago, foft said:

Yeah the pads did seem pretty big when soldering parts on. Eagle definitely shows 0402 on the bom. Did I do some weird imperial/metric screwup or something?

 

They don’t look that large, just a bit more than necessary

 

Yeah, a metric screwup is one possibility. The large pads are fine for hand soldering, but it bothered the JLC engineers for automated assembly as they claim there's risks of weak connection, bad soldering, tombstoning. I've attempted to replace the parts with 0603 equivalents, we'll see how that goes. If it fails, I'll change the footprints for real 0402, that's fine, there aren't that many. Also, on my own version, I'll use standard 0402 footprints.

Thanks for confirming, much appreciate the help.

[foft]

Doing some more reading… Apparently the IPC standards have been revised. I used the rcl library from my old version of Eagle. I guess if you are in Kicad you can change them to the modern footprint.

[ScreamingAtTheRadio]

All right. So I'm done with the redesign of the board. As stated above, I've prioritized JLCPCB availability on this one, and minimized the design for the simplest stereo Pokey. I just ordered a new batch of 5 for... $150.44, shipping included. Not bad at all, that's about $30 for an assembled Pokey, and all you have to do is upload 3 files. The least available components are the level shifters and the FPGA (you may have to pre-order those).

 

Here's the new board:

Changes from the original design include:

- Larger pad holes for the main connector, so you can mount precision pin headers right through the board (I had mine made in 1mm thickness). This makes a chip that's not tall at all, and that you can plug header cables right into...

- Removed GND from the audio connector, there's one right next on the JTAG connector.

- Used Kicad standard footprints where possible.

- Added legends for all pins on the silkscreen.

- Used smaller 20-line level shifters instead of the original 24 line ones. That means the expansion port that was on the bottom of the board is also gone, except for the AUD_IN that I moved where I had some room.

 

And that's pretty much it. This thing should be pretty much compatible with @foft's design and VHDL.

 

Production files can be downloaded from here: https://github.com/bleroy/pokeymax/tree/main/PokeyMax4s/production

All sources available on the same repo.

 

One thing I wasn't sure about is what the third pin on the audio port is doing (labeled MO by me on the PCB as a bad guess). It's connected through the level shifters to the FPGA's pin B13, labeled LIN21. I tried to follow that through the VHDL code, but that's currently way above my head. I'm suspecting that's where SPDIF can go but I wouldn't mind a confirmation.

Edited August 25 by ScreamingAtTheRadio

[_The Doctor__]

Mono Right Left or motor? I'm thinking down that path

[ScreamingAtTheRadio]

Well, unsurprisingly I missed one thing, at least. I cancelled my order and advise nobody orders anything based on the current files. Thanks to @flashjazzcat for pointing that out: I'm missing A4. I still have one available level shifter line so that should be ok, if slightly problematic to route given how tight it already is.

[ScreamingAtTheRadio]

Should have paid better attention to the beginning of this thread. This post has the detailed pinout:

So the mystery pin is SPDIF, and I know where to find A4. Now I'm actually out of 1 line if I want to include both SIO clicks and GTIA 15 keyboard noise. So what do people think?

You can have only two out of those 3: SIO noise, keyboard clicks and SPDIF.

 

Edited August 26 by ScreamingAtTheRadio

[flashjazzcat]

As long as GTIA audio is there.

Edited August 26 by flashjazzcat

[foft]

Nice job 👍
 

10M02 has no flash (no space for the flash controller). So I’d stick with 10M04 for a plain stereo which allows upgrading without jtag and some settings.

 

Regarding level shifters. They just prevent the fpga seeing 5v. I route almost everything through them for simplicity though in reality things that will never be pulled higher than 3.3v do not need to go through it. Eg spdif out.

 

As fjc says having A4 and GTIA in would be good as a minimum. SIO audio in is already handled by the ADC. On prior versions to v3 I didn’t have that so mixed sio data noise internally.

 

Another possible cut to the bom is to remove the oscillator, I only need it for spdif.

[madness77]

18 hours ago, ScreamingAtTheRadio said:

- Used smaller 20-line level shifters instead of the original 24 line ones. That means the expansion port that was on the bottom of the board is also gone, except for the AUD_IN that I moved where I had some room.

 

6 hours ago, foft said:

Another possible cut to the bom is to remove the oscillator, I only need it for spdif.

 

The concept of creating a minimum version without unnecessary components and outputs is perfectly OK, but if you extended the PCB by 0.5cm you would fit a connector with additional pins for the "maximum" version. What do you guys think about it?

[ScreamingAtTheRadio]

7 hours ago, foft said:

10M02 has no flash (no space for the flash controller). So I’d stick with 10M04 for a plain stereo which allows upgrading without jtag and some settings.

Regarding level shifters. They just prevent the fpga seeing 5v. I route almost everything through them for simplicity though in reality things that will never be pulled higher than 3.3v do not need to go through it. Eg spdif out.

As fjc says having A4 and GTIA in would be good as a minimum. SIO audio in is already handled by the ADC. On prior versions to v3 I didn’t have that so mixed sio data noise internally.

Another possible cut to the bom is to remove the oscillator, I only need it for spdif.

Thanks, this is extremely helpful. I'll see how 10M04 changes the price when I send the new board for fab, good to know about upgrades.

 

I was curious about needing the shifters for output signals not going into the Atari, thanks for confirming that I can take SPDIF off the shifters if I need the line, but then again if I only need A4 and GTIA 15 in, that may not even be necessary. Any suggestion about what else I could do with that extra line?

 

I'll probably keep the oscillator and SPDIF on the board but good to know there's the option to skip it. In fact, that might be an option to call out in docs if people want the cheapest possible PokeyMax.

 

1 hour ago, madness77 said:

The concept of creating a minimum version without unnecessary components and outputs is perfectly OK, but if you extended the PCB by 0.5cm you would fit a connector with additional pins for the "maximum" version. What do you guys think about it?

My goal with the redraw is to get the cheapest Pokey replacement, as vintage Pokeys have become Unobtainium and reach insane prices on the used market. It's for people who maintain Ataris and need to replace Pokeys. For upgrades, the maxed out version already exists, it's Foft's original board, which can be built from the files he made available or bought fully assembled.

[Panther]

Well, I'm finally back for awhile from multiple trips out of town and decided to get back to work on some of these projects I have sitting here, starting with building my PokeyMax board.  I really need it for my Atari 800 that's been sitting here in pieces for far too long.  So, I took out one of the PCBs and cleaned it, got out the solder paste, set up the heating pad at the microscope, and then collected all the components...or, almost all.  I couldn't find the oscillators.  After searching everywhere I could think of for them, I eventually went through all my orders...they aren't listed!  Somehow they were skipped back when I ordered the components in June.

 

Oh well, I have other projects I can finish while waiting for the oscillators.

 

[madness77]

4 hours ago, Panther said:

Oh well, I have other projects I can finish while waiting for the oscillators.

23 hours ago, foft said:

Another possible cut to the bom is to remove the oscillator, I only need it for spdif.

 

So if I understand correctly, you can still make a working PokeyMAX without an oscillator, which is only needed for SPDIF digital audio output? Right @foft?

[Jacques]

On 8/25/2024 at 11:03 PM, ScreamingAtTheRadio said:

and minimized the design for the simplest stereo Pokey.

Out of curiosity, is it just 2x Pokey instead of 4x Pokey, with PSG, MOD and SID support still there?

Edited August 27 by Jacques

[foft]

1 hour ago, madness77 said:

 

So if I understand correctly, you can still make a working PokeyMAX without an oscillator, which is only needed for SPDIF digital audio output? Right @foft?

Correct. It does need a different core though.

[foft]

1 hour ago, Jacques said:

Out of curiosity, is it just 2x Pokey instead of 4x Pokey, with PSG, MOD and SID support still there?

The cut down board just has stereo. The others need a larger fpga and more io for address pins.

Edited August 27 by foft

[+Larry]

19 hours ago, ScreamingAtTheRadio said:

Thanks, this is extremely helpful. I'll see how 10M04 changes the price when I send the new board for fab, good to know about upgrades.

 

I was curious about needing the shifters for output signals not going into the Atari, thanks for confirming that I can take SPDIF off the shifters if I need the line, but then again if I only need A4 and GTIA 15 in, that may not even be necessary. Any suggestion about what else I could do with that extra line?

 

I'll probably keep the oscillator and SPDIF on the board but good to know there's the option to skip it. In fact, that might be an option to call out in docs if people want the cheapest possible PokeyMax.

 

My goal with the redraw is to get the cheapest Pokey replacement, as vintage Pokeys have become Unobtainium and reach insane prices on the used market. It's for people who maintain Ataris and need to replace Pokeys. For upgrades, the maxed out version already exists, it's Foft's original board, which can be built from the files he made available or bought fully assembled.

Bravo!

[ScreamingAtTheRadio]

Here's the revised 4s board with SPDIF, A4 and GTIA 15:

One more question for @foft: I looked at the price difference between 10M02 ($5.16) and 10M04 ($16.55), so there's a strong incentive to keep 10M02 since 10M04 would add >30% to the price. Is the only practical disadvantage that it can only be programmed through JTAG?

 

Note: the oscillator only adds 44c to the price so it seems like it's not really worth removing.

[woj]

I am not sure M02 even fits SPDIF? Not having Flash also means no permanent config changes (not many options in the bare config, still some). Having to flash the core through JTAG is not that much of a limitation in your case, because one still need to boot flash it, and that JLC won't do I guess...

 

I also had to decide on the M version when cooking up mine, it seems that M04 and M08 are very closely priced and M08 goes rather far with what it can fit, but of course here it is a kind of no go.

 

[I still regret I did not go for M16, I was just too afraid of destroying it and wanted first to experiment with something cheaper, as it turns out the experiment became the final product 😅].

[madness77]

@ScreamingAtTheRadio I know it's just an aesthetic thing, but since the components fit, what would you say about putting all the electronics underneath?

 

Like SIDKickPico or ARMSID?

    

 

(by the way, soldering the legs will be easier, 0402 components are so close to the pads)

Edited August 28 by madness77

[foft]

5 hours ago, ScreamingAtTheRadio said:

Is the only practical disadvantage that it can only be programmed through JTAG?

Yes, that and the ability to save any settings with power off. Also the spdif logic might not fit though.

 

Surprised by the price difference. I was thinking it’d be about 1-2usd more. It is 8 vs 11 on DigiKey and I thought via jlcpcb it’d be less.

So for the low cost model probably makes sense to keep the 10M02.

[foft]

2 hours ago, madness77 said:

what would you say about putting all the electronics underneath?

For manual assembly it’s harder since any rework is between the legs.