A few years ago I purchased a cheap USB modem with the idea of building a "PC/DC server" and connecting my Dreamcast to the Internet. When it arrived I couldn't find the time (and didn't have the skill) to build the required line voltage inducer, so the modem sat in a drawer untouched.
Later, the Raspberry Pi was released, and I bought one. I figured it was time to finally build that PC/DC server! But alas, like most Raspberry Pi purchases it ended up in the drawer alongside the USB modem, like pieces of an incomplete jigsaw puzzle.
Fast-forward to 5 months ago. Since buying the modem my electronics skills had improved considerably so I finally built that line voltage inducer, and tried to configure the PC/DC server with the Raspberry Pi. It didn't work. I tried everything! Different resistors, different batteries (up to 12V) , I rebuilt the line voltage inducer twice. It still didn't work.
Then someone on a forum said it seemed like there wasn't enough voltage. I couldn't understand that - all the tutorials had said 9V was plenty, I was using 12! One day I got reckless and connected two 9V batteries rather than one, and straight away Phantasy Star Online connected! It was at that point that I realized that I'd never actually seen anyone with a PAL Dreamcast manage to get a PC/DC server working, I'd seen plenty of people with PAL Dreamcasts complaining it didn't work however. This was the mystery solved! PAL Dreamcasts need more voltage than the U.S. counterparts.
At this point connecting was a pain. I had to connect to the Pi, launch a program, and then dial on the Dreamcast, then answer manually on the Pi. "Surely there's a better way", I thought.
It occurred to me that the USB modem could "listen" for the Dreamcast dialling. If it could then I wouldn't need to answer manually, I could write some code for that. I opened up my editor and started learning HAYES commands to talk to the modem. I put it online and waited until the Dreamcast dialled, and then answered. Success! After making sure that I could repeat the process automatically I pushed out a release of the DreamPi image. People were happy, but there were still problems...
Most games look for a dial tone before they will try to connect to a remote server. Obviously there is no dial tone when you've just connected one modem to another. While browsing for information I discovered that someone had built an interesting solution by connecting the line-out of a computer to the phone line, and played a recording of a dial tone into the line until the Dreamcast dialled. Then there was another "eureka!" moment. I already had the line open while I was listening for the Dreamcast to dial numbers, I could definitely play the sound of a dial tone through the modem at the same time.
It took a lot of fiddling to find the right set of HAYES commands, but eventually I succeeded. Now all Dreamcast games would work! It took several more bug fixes and releases to get to where we are today. But here we are at version 1.0.
So, today I'm announcing 1.0. This release extends the timeout for waiting for command responses, and doesn't echo our commands back to the modem which was confusing things.
There is still more to be done. I'm not happy with the IP address allocation, and WiFi support has always been on the list. But I'm happy to call this release complete. You can now play your Dreamcast games online with nothing more than a USB modem, a Raspberry Pi and a simple electrical circuit.
My next challenge is to get a Dream Arena authentication server running. At that point the last remaining games (Toy Racer and PAL Q3 Arena) will work and the DreamPi will allow playing every online game that still has servers.
Merry Christmas everyone!