Sega Dreamcast USB Coder's Port tutorial

[einsteinx2]

@darcagn heard back from him already Here's his response:

Interesting! Let me take a close look. Basically, it is not hard to customize a cable with connectors. I have done a few power supply cable customizations for other tablet projects.

I sent him photos of the dreamcast serial port and a homebrew sd card adaptor I bought from eBay as examples, and asked if it was something he could do (or if not, could he refer me to someone he knows that can), and I would just need to know what the minimum order size was and a rough cost estimate to see if it was feasible. I'll post again when I know more, also feel free to PM me if you want (I'm also on Discord, same username).

He asked me to write a formal product request so that he could forward it to potential manufacturers, so I'm getting more info on that now.

 

[Cooljerk]

Slightly off-topic here, but given the unique talents of the people around here, if anyone knows what it takes/who to work with to get serial connectors for DC made in large quantities, I would love to see that happen.

I've been playing around with KiCad to try and make some small serial boards but I'm really not good at it. I got the idea when I bought some USB LED light boards that look like this:



Someone already makes a breakout board for the serial port, but it's intended to be surface mounted inside the DC:



but it requires quite a bit of soldering on some thin pins inside the dreamcast. What I have in mind should be a single PCB with traces running to breakouts that could slot directly into the serial port on the back of the dreamcast, no internal modification needed. Unfortunately, I kind of suck with kicad, but if something like this could get off the ground, you could print up a few of these things on something like Ohspark for relatively cheap, as in something that would be affordable on an individual order basis. For reference, last time I built some UMDKs, I was able to order about 6 large PCBs from Oshpark for around $50 including shipping.

edit: the existing breakout board project page: https://pomegd.hatenablog.com/entry/2019/04/06/230000

they cost about $9 USD.

 

[einsteinx2]

Oh that's a really cool idea! Basically like existing FTDI boards (like the one used in this guide) but printed on a thicker PCB with the correct contacts at the end to slide right into the connector. Seems like it's fairly common the USB side of things (boards that slide right into a USB port), maybe that would be a way to do it much cheaper since it would only require getting circuit boards fabbed instead of whole cables.

I'm interested in seeing the quotes I get from my contact in China. If they're cheap enough, full cables would still be a cool option, but an open source circuit board that anyone can order from an online fab and populate (or order pre-built if they want) would be an awesome option to have available).

 

[FamilyGuy]

Oh that's a really cool idea! Basically like existing FTDI boards (like the one used in this guide) but printed on a thicker PCB with the correct contacts at the end to slide right into the connector. Seems like it's fairly common the USB side of things (boards that slide right into a USB port), maybe that would be a way to do it much cheaper since it would only require getting circuit boards fabbed instead of whole cables.

I'm interested in seeing the quotes I get from my contact in China. If they're cheap enough, full cables would still be a cool option, but an open source circuit board that anyone can order from an online fab and populate (or order pre-built if they want) would be an awesome option to have available).

I think both are nice, but a high quality connector would be the best.

The serial connector is much too thick for any PCB, it'd require some kind of shim.

 

[einsteinx2]

Looking at the SD card adaptor I have, it looks like they did exactly that except with probably a piece of an AGP slot connector. Just glued a plastic shim to the bottom. Would be easy enough to have boards made and do exactly that. Though I do notice that on the connector it uses, the pins stick up a bit, so I'm not sure if flat PCB pads would even make a connection actually...

Anyway, I'm making a diagram for the custom cables with the exact components needed, exact measurements on the port, pin width, and pin spacing, and all other information and passing it to my contact tomorrow. He can definitely get them made, the only question will be how big does an initial order have to be and what is the upfront cost...

Ideally, one of the manufacturers will be able to find a suitable mass-produced connector that matches the pin spacing and width to keep from having to make something from scratch, but I'm not sure what--if any--tooling costs would still be required to make the custom end (things like plastic injection molds are expensive, but if they can find a way to re-use molds from another product we could get lucky and skip that part). But at least once the mold is made, you can keep ordering more at only the cost per unit.

The real question is how big is the market for this? Hundreds? Thousands? If the order is too small, the cost per cable including tooling/molding costs could be prohibitively expensive. I'd say at least for the first run (as later runs would be cheaper) the cost would have to be at least less than half the cost of a BBA, which right now seem to go for around $150 or so. So I think if it was possible to get the first run's price to consumer (not production cost) to $50 or less, then it would make sense. Higher than that and I'm not sure how many people would want one.

But anyway, too many variables until I hear back from the manufacturers, so I'll hold off any more speculation until then. Maybe it turns out they can be made for a few dollars, who knows.

 

[Cooljerk]

Oh that's a really cool idea! Basically like existing FTDI boards (like the one used in this guide) but printed on a thicker PCB with the correct contacts at the end to slide right into the connector. Seems like it's fairly common the USB side of things (boards that slide right into a USB port), maybe that would be a way to do it much cheaper since it would only require getting circuit boards fabbed instead of whole cables.

I'm interested in seeing the quotes I get from my contact in China. If they're cheap enough, full cables would still be a cool option, but an open source circuit board that anyone can order from an online fab and populate (or order pre-built if they want) would be an awesome option to have available).

Right, I'm actually not sure if they can produce a thicker PCB, but someone could 3D print a spacer to be glued to the back of one to make it fit snug. I have a 3D printer, I just don't have access to something that can make PCBs quickly, so I'd have to actually order a prototype from Oshpark every time I wanted to test a design, which is why I'm trying to go slowly with KiCad. If anyone has some equipment that could test a PCB quickly at home, this would actually go much faster and easier. As is, it takes Oshpark like 2 weeks to get a prototype gerber file printed and shipped to me.

Though I do notice that on the connector it uses, the pins stick up a bit, so I'm not sure if flat PCB pads would even make a connection actually...

I'd thought this as well, but I think the reason they use those pins with a bit of bend in them is because on the DC serial port, on the left and right side, there are very slight lips that makes a connection stand up a bit off the connection. So any pins on their stick need to reach down to overcome the lip. I actually have a dreamcast where I broke the plastic bit of the serial port off (as in, the internal plastic bit, not the shell on the outside) and the pins on the serial connector lay flat. I *think* if that lip is accounted for in whatever PCB exists could still work. But again, all of this would require pretty extensive prototyping to make sure everything was exactly the right measurement. At 2 weeks a prototype, this just moves way too slowly.

 

[einsteinx2]

No need to even go with 3d printing for something like that, just laser or cnc a bunch of acrylic squares to glue to the end that goes into the port. Probably even possible to just order them cheap.

 

[einsteinx2]

But a full enclosure that includes the spacer would be a cool 3d print for people with printers.

 

[Cooljerk]

But a full enclosure that includes the spacer would be a cool 3d print for people with printers.

you found out my secret, haha. I'm always looking for ways to actually use my little printer. It's so cool... it's just not a lot of use when you're bad at designing files to print like I am lol

 

[einsteinx2]

I really want to get a printer, mainly for custom project enclosures, just waiting on the money

 

[Cooljerk]

I really want to get a printer, mainly for custom project enclosures, just waiting on the money

I have a monoprice select mini 3D, they've been pretty consistently the cheapest 3D printer. It was like $300 when I got it, but I'm pretty sure they're below $100 now.

I have access to a hackerspace where they have nicer 3D printers, too. I'd love a really expensive one with an enclosure and all the nice stuff that goes with that. I have my mini select decked out with a RasPi for wireless monitoring and a remote server type stuff, and a glass bed and an entire crate of aquanet so I try to make the best with what I got, haha.

I just wish I was better at using CAD programs in general.

 

[einsteinx2]

@Cooljerk sent you a PM so we don't derail the thread chatting about 3d printing

 

[einsteinx2]

I've sent a full diagram with all info necessary for the manufacturer quotes for the custom manufactured coder cable including caliper measuremets of the port and pins, a pin diagram of the port, pin connections from the FTDI chip to the port, and description of all components required.

I'll report back when I get some quotes on manufacturing costs and other info needed to move forward with a potential order.

 

[einsteinx2]

Also it occurs to me that if we do end up getting these made and they are already producing the serial port connectors, they could also make system link cables! Just leave out all the electronics and wire the ends directly to each other (with the correct wires crossed over correctly) and boom, system link cable. Shouldn't even require any new tooling, so maybe a small run could be made after an initial order of coder cables.

 

[FamilyGuy]

Also it occurs to me that if we do end up getting these made

The ideal for tinkerers, and probably the cheapest, would be to just sell a serial connector, or a breakout cable (connector on one end, naked wires on the other).

Selling full fledged coder's cable or their usb counterpart might not be a great ROI.

 

[einsteinx2]

That's a great point, as it could be used for both cases, making SD card adaptors, or really anything you want. I'll ask him to get quotes for both the full cable and just the serial connector with breakout board.

 

[einsteinx2]

Here are the 2 diagrams I sent him (plus I sent some example photos of the original cable, the port, and a homebrew SD card adapter for reference).




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[darcagn]

Also it occurs to me that if we do end up getting these made and they are already producing the serial port connectors, they could also make system link cables! Just leave out all the electronics and wire the ends directly to each other (with the correct wires crossed over correctly) and boom, system link cable. Shouldn't even require any new tooling, so maybe a small run could be made after an initial order of coder cables.

It would be much more preferable to have the connectors only, given there are multiple uses.
- Coder's cable
- System link cable
- SD card adapter
- NeoGeo Pocket color link cable
- MIDI adapter for Otoire Dreamcast Sequencer
- Serial loopback cable (used for Sega DC Checker diagnostic software to ensure the serial port works)

Just like the A/V connectors you can get in low quantities from console5 or you can buy them in quantities of hundreds on aliexpress etc.

 

[Cooljerk]

It would be much more preferable to have the connectors only, given there are multiple uses.
- Coder's cable
- System link cable
- SD card adapter
- NeoGeo Pocket color link cable
- MIDI adapter for Otoire Dreamcast Sequencer
- Serial loopback cable (used for Sega DC Checker diagnostic software to ensure the serial port works)

Just like the A/V connectors you can get in low quantities from console5 or you can buy them in quantities of hundreds on aliexpress etc.

One other dream use for me: the mythical GP32 link cable lol

 

[einsteinx2]

I'll pass along the comments about manufacturing just the port connectors. Since that would need to be done regardless, I'll ask for a quote specifically just for those.