Written by Yuji Yokoo (@yujiyokoo on Twitter), May 2019
A lot has changed in this area since when I did this. Please take a look at the page on Coder’s Cable at Dreamcast Wiki. There is information on updated components as well as commercially available cables. I am keeping this information as is, hoping it will still be useful to some people who build their own cable.
Please see: https://vimeo.com/336989348
It took "94.99 seconds to transfer 967020 bytes".
There is lots of useful information on the Internet. However, there were 2 web pages I really looked at for cable construction. They both contained useful information, but neither one seemed to be exactly what I needed.
I based my design mostly on this, but this page seems to be primarily for modifying a DC-to-NeoGeoPocket cable. Also, it could just be me not reading it correctly, but I’m not sure if receive and send pins are connected correctly. http://mc.pp.se/dc/serifc.html
I also looked at this page to try to figure out which pins should connect to which pins (Japanese). Note this page is NOT about cable construction. It shows how to build a DSUB-9 serial port on DC. This page shows MAX232, not MAX3222 but the receive pins and transmit pins have the same names, so it helped me. http://niga2.sytes.net/game/dcrip.html
Also, this page in Japanese shows you pin numbers on the DC serial port (the photo near the bottom of the page): http://jj1odm.qp.land.to/dcserial_ft232bm.php
The cable connects from Dreamcast’s serial port (sorry about the poor picture, but I do not have a good camera or a macro lens):
with the connector:
To the serial communication board (main part of what I built):
To the serial cable end:
Which connects to a DSUB-9 serial port (in this case, a USB-to-serial cable):
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1 x Dreamcast serial connector. I sourced this by breaking up a Dreamcast SD-card reader, but it was very hard to use. It’s supposed to be a lot easier with a DC-to-Neogeo Pocket cable.
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1 x universal circuit board, which looks like this:
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1 x MAX3222, with through-hole, not surface-mount (In my case, I bought a MAX3222ECPN): + https://www.maximintegrated.com/en/products/interface/transceivers/MAX3222.html + If you use a universal board like I did, it’s important to get a through-hole one, not a surface-mount. + The data sheet can be found here: https://datasheets.maximintegrated.com/en/ds/MAX3222E-MAX3246E.pdf
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4 x 0.1uF (or 100nF, same thing) capacitor
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1 x female DSUB-9 connector
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1 x DSUB-9 housing (note, this is slightly different from the one I used)
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Some insulated wires + I used what I had at home, but they were a little thick, and should have bought some thinner wires.
This is a photo of my final build:
This is a photo of the back (soldering side) of the bard:
These SD-card adapters you can buy online don’t seem to be built very well, especially if you want to brake them up and reuse the connector. I would not recommend it, but there is no other reliable source of connectors that I am aware of.
Please be careful when you solder pins for both DC and DSUB9 serial ports. Please note the connector on the DC side goes in with pins facing down. Please be aware the side for soldering is flipped from the connector side for the DSUB9 serial port.