shmups.system11.org

UPDATE 4/16/19
At this point the mod has reached a level of polish that I am satisfied with releasing it officially. As such I have decided to update this post with all of the information about what this mod is and does.



What is it?
This mod is the result of an effort to combine Borti4938's high quality RGB Bypass mod with Marqs85's SNES Dejitter mod. It allows for a simple and clean installation of both mods with minimal wiring. It is compatible with SNES 1CHIP and SNES Mini/Jr. models.

Features of the Mod (What does it do?):

-High quality RGB Bypass based on the design by Borti4938.
-S-Video restore for SNES Mini/jr.
-TTL C-sync restore for 1CHIP-03 models.
-C-Sync dejitter functionality from Marqs85’s SNES Dejitter mod project.
-Optional logic level C-Sync output for adding dejittered S-Video and Composite video through the S-RGB encoder.
-Ability to disable dejitter functionality on demand.

Video Overview and SNES Mini Installation Demonstration

Where to get it.

I have released board files on OshPark if you want to have your own manufactured. The BOM for the project is available for download from my website here. Firmware for the Dejitter portion of the mod can be found at Marqs85's Github

With multiple fine pitch SMD packages and very small 0603 components this is not an easy build. If you are not confident in your ability to build it yourself I do have fully assembled and programmed boards available in my modding shop. I can also perform installation service as well.

I'm still working on documentation for those who will be doing their own installations. It's pretty easy to install but there are some special considerations depending on which model of SNES you are installing. When I have that ready I will post it on my site also.



Original Post:
I've been RGB and dejitter modding quite a few SNES Minis lately, which currently involves installing both the Dejitter board and a separate RGB bypass mod. Since I forsee many more SNES Minis in my future I decided to spend the day trying to combine the RGB bypass and Marqs' dejitter mod into one easy to install PCB. This is what I have so far.





The design is derived from Marqs' v1.2 Dejitter board and Borti's RGB bypass V4.1a with S-Video. I'm fairly new to PCB layout so there may be some issues that I haven't accounted for. As such I'm not releasing the gerbers until I receive my prototypes from OSHpark and can test for any problems. If all is well with the design it should make for a really easy all in one SNES Mini and 1-Chip mod.

Let me know what you guys think.

You should add ability to control LPF on THS7374.

Also. the decoupling caps on the multiout. in some instances only 1 of the 4 is needed. it would be handy if they were actually named rather than C*4

I wonder how this will perform. I know on Sega Genesis routing analog video lines next to the crystal was a big source of jailbar noise.

Beware of fast switching logic near sensitive analog video.
I suppose the CPLD drives a couple 21Mhz lines, right?
I'm no expert on this, but there should be a few nice videos on Youtube on the topic.
Look for for mixed signal / high speed pcb design stuff

J11 allows you to toggle the LPF on and off. I am concerned about the analog video lines being so close to the crystal also. It kind of happened on accident as I was pulling the two board designs closer togerther.



We'll see how the current design fares, I'm expecting some degree of failure with this first attempt. I've got some waiting to do until I get the first batch of boards so I'll probably go ahead and proactively rotate the layout of the dejitter components to get the crystal away from the analog lines. Doesn't seem like it could possibly hurt.

Thanks for the feedback guys this is what I was hoping for.

I think this is great. I'd really like to see a small switch for the THS7374's LPF if that's possible, with markings on the board. It just makes things easier:



Also...and excuse me if this is a dumb question...but would it be feasible to have the dejitter be a switchable option? This way speedrunners can still use it without worrying about a second lost here or there?

I hate to bring it up here, too, but in order to lose even one full second, you'd have to be playing for at least 30 hours straight. I believe Marqs said it is less than 2 frames slower over the course of an hour, which, as discussed in another thread, is well within the tolerances of the crystal itself. Which is to say that comparing the speed of two consoles (neither with dejitter installed) would yield at least as much difference as the same console with and without dejitter. I'm not necessarily saying don't put in a toggle, but realistically there is no reason to devote time to designing it.

I could definitely integrate a physical switch for the LPF if that is a desired feature.

As far being able to switch the mod off, I don't know if that would be practical. The mod entirely replaces the original SNES clock circuitry, so if I understand it correctly you would have to switch between the original and new clock circuit as well as the original and dejittered Csync circuit. It may be doable, but it's probably easier to have one modded console and one unmodded console for speedrunning.

it's def possible - marqs explained it in the original thread

something along the lines of wiring the original clock circuit to MCLK_EXT_i and then pulling the CLK_SEL_i high when you want to switch it off IIRC

Ok cool. It shouldn't be too difficult add the MCLK_EXT_i and CLK_SEL_i pads back to the board so a switch can be wired to it. I'm probably going to need to reorganize the board anyway so I might as well offer the option.

I'm going to go out on a limb and say that a given mod does not need to be everything to everyone, especially before its first revision has even been built.

If a speedrunner is concerned that a dejitter mod is going to screw with times, but still wants a system with dejitter, the SNES is still common enough that it would be practical to own two systems, one with a typical RGB bypass, and another with an RGB bypass plus dejitter mod or the proposed combo board.

If people are honestly worried about how the dejitter mod will affect times or performance, get some empirical data by comparing a few runs of a TAS running on each of 4 or more systems (a mix of 1- and 2-chip for good measure) before and after installing a dejitter mod. If it takes 30 hours to drift 1 second, I expect most SNES speedruns to ultimately be unaffected.

(Typed before seeing that a dejitter toggle switch is possible )

Agreed. Adding the clock source switcher complicates the design lots.
The different clock signals will have to travel all around the system, creating lots of noise, too.

The idea of an hour-long real time run being optimized to within a frame or two is pretty silly anyway. Most leaderboards don't even bother tracking times to sub-second precision for runs that are more than a few minutes long. I'm all for choices as long as they don't negatively impact the design, but if it makes things complicated I don't think it's worth worrying about.

Notably, these forums have a lot of talk about things that speedrunners might want without a lot of input from actual speedrunners :p One of the few notable speedruns that is tracked sub-second is Super Mario 1, but at less than 5 minutes, I suspect it would be over before one would notice any difference. As others have mentioned, at the length of play time it would take for the difference to become evident, the leaderboards no longer track increments less than 1 second anyway. And at lengths less than that, not enough time has elapsed to see any difference. Either way, it's not really necessary to toggle.

That's one way to look at it. Another is maybe ask the questions now, before someone spends all the time finishing it up. What if it was a quick thing?

...but unless it's an easy addition, I wouldn't bother. Just wanted to ask. Backing away slowly before I trigger more of you...

Major layout revision to get the analog lines as far away from the crystal as possible.





Thoughts on this layout would be appreciated.

I think it's good to have soldering pads or jumpers to turn LPF and de-jitter on or off. It's alway nice to have options. Given the opportunity, I feel everyone would like to see the differences themselves on their own set-up and not having to wonder if they are missing out. If nothing else it's a great way to diagnose your install or set-up if there are issues.

I designed and installed a switch mount so I could turn on LPF for my install of Borti's board when I sit very close to my large screen where I could see some noises sometimes. When I sit farther, I turn it off to regain some sharpness since the noises are too small to be seen from a distance.







I don't own an OSSC yet, but I might in the future so I'm getting ready to install marqs' board and be ready. I recently wrap up designing a dual switch set up just so I'm covered.

That is damned nice, BuffaloWing! I'll take two.

Seriously. I have two SNS-101s and two Super Game Boy 2s and I can't just have one of my systems dejittered and possibly messing up the link process.

See thread above. It actually has ability to control LPF already. But he calls it JP1. If it was called LPF or something that makes more sense, it would be much more helpful. How difficult would it be to silk screen "close JP1 to disable LPF" on the back side?

I had some time to work on the board some more and I have added pads for Mclk_ext and Clk_sel for those who want to add a switch to turn the dejitter on and off. I also moved and changed the label for the LPF jumper so it is easier to read and also to use as pads for wiring an on/off switch.







That is awesome. do you intend to sell those anywhere?

According to marqs' FAQ, Pin 34 on CPLD also needs to connect to MCLK_EXT_i pad in order for the disable function to work. If possible, it might be useful to include jumper pads (to the right of your existing MCLK_EXT_i pad) that route those two path together. This will eliminate the need to solder a short jumper wire, however I don't know if routing those lines in a crowded board will create unwanted interference or not.


Yes, if people are interested. However, I think most people are probably satisfied by just hot gluing. I'll probably end up just put the file up on Shapeway for someone who are interested in purchasing the mount and have them produce the PCB themselves.

Any reason why capacitors C*4 are not sequential on the PCB?

it's an artifact from the original RGB bypass design from Borti4938. I plan to go through the board and tidy up the component names and silk screen once I confirm that it actually works.

I have the SNES board already but I’m struggling to find the correct instructions to install on my 1-chip 03 sync on luma machine. Could anyone please point me the way?

Thanks

Well I've got the V0.2 prototype from Oshpark and I got it installed today.

It appears to be working. I need to do more extensive testing but I haven't encountered any visual artifacts yet. The board layout needs more work though. I failed to account for one of the screws and standoff near the AV connector so it will not properly fit in the SNES mini shell without modification. That will be the next priority.

Here's a youtube video of the install.

Just wanted to leave a quick update, I've had time to do more extensive testing on this mod and I discovered faint jailbars in dark scenes with my original installation. I was able to get rid of them by rerouting the clock wire around the RGB and Sync wires instead of under them like I originally had it.


At this point I can't see any problems with the image produced by this mod. I also had some time to rework the layout so it clears the screw post to the right of the AV port and I have prototypes of that board ordered as well. I also changed up the Csync circuit on this version so that it is buffered through the THS7374 like in Borti's original RGB Bypass mod instead of using marqs' Csync output circuit from the original Dejitter board. This change reduced the component count and saved quite a bit of space on the board.

interesting... I'm having jailbars on my SHVC-CPU-01 with dejitter install as well

my clock line doesn't cross the csync output, but it does cross the csync input at one point

unfortunately I don't know if they were present prior to the mod or not

The newest prototypes arrived today and I had some time to assemble and test one.


The changes to the CSYNC circuit worked great. It now works exactly the same way that Borti's original RGB Bypass Csync circuit does. It pulls logic level CSYNC directly from the CPLD and sends it through the THS7374. Another great feature that this version of the mod adds is that it actually fits inside the SNES Jr shell!

So with that said, I have revised the board one more time to add a few of the features that people have asked for. This will likely be the final version of the design barring any major developments.



A couple of notes on the features of this version of the board.

J1: On the lower left corner of the board I have added a jumper called J1. J1 connects Mclk_ext_i to Mclk_xtal_o. If you close this jumper you can add a switch between Clk_sel and 5v which will let you disable the dejitter function.

LLCS Pad: On the right side of the board I have added a pad above the S-Video pads called LLCS, this stands for Logic Level CSYNC. There has been some discussion over in the main Dejitter thread about wiring dejittered CSYNC directly to the CSYNC input of the SNES's onboard video encoder to provide dejittered composite video and S-Video signal. The LLCS pad connects directly to the 5V CSYNC output of the CPLD. On a SNES jr you simply need to lift pin 7 of the S-RGB encoder and wire it directly to the LLCS pad to get dejittered composite and S-Video.

Extra Ground Pad: I added a ground pad next to Mclk_o to make it easy to use coaxial cable for the clock line, since it needs to travel a longer distance around sensitive areas with this mod I think it would be good practice to use Coax if you can.

Well I think that about does it. I've sent off to have copies of this newest design made and I'll report back if there are any problems, but I think I'm comfortable releasing it now. Here is the board on OshPark if anyone wants to try making one. I'll of course be stocking them on my website as well once I've tested the final version.

Here is a download link to the BOM for this project.

looking really solid man!

(btw my jailbars got fixed by adding 10uf caps to the PPUs/CPU/WRAM/VRAM, not dejitter related)

I've finally had a chance to assemble and test the final revision of the board. Everything is working as expected so I am calling this mod done. I've updated the top post of this topic with the most current information about the mod. It's open source so board files are available and I also have assembled boards available on my website for those who do not want to build their own. Stock is limited right now because I only have pcbs from the final prototype run, but I have a larger order of pcbs being manufactured as we speak so availability will be much better in a week or so.

I'd like to thank everyone here for their suggestions for this mod. I learned a ton about designing PCBs and I think I was able to find compromises to make everyone happy without falling prey to excessive feature creep. I hope you all agree.

Awesome work! I missed ordering the few you had in stock. Looking forward to you getting some more in and ordering ASAP. Looks like the perfect one-stop mod for my 1-chip-03! Thanks for doing this!