Monday, August 4, 2008

Connecting a Dreamcast to the Internet

All Dreamcasts came with a dialup modem.  There was an ethernet adaptor for it but only a few were sold before Sega pulled the plug on the Dreamcast.  So, what I wanted to do was get it connected to the internet without pulling up a giant phone bill (and possibly internet fees).  You could get one of those prepaid dialup cards you can get from your local convenience store, but most people (me included) already have a broadband connection at home.

My plan was to connect it to another dialup modem with nothing more than a phone cable between the 2.  This did not work at all.  The modems are expecting some kind of phone line with some current flowing through it.  What I did would be similar to connecting 2 handsets together with some phone wire.  You can talk as loud as you want, but nothing is going to come out of the other phone's speaker.

What I need is some kind of line simulator that will fool the modem(s) into thinking that it's actually connected to a phone line.  I found this after some searching  After obtaining the parts and assembling it together:

It did not quite work out.  Same as before, nothing. NO CARRIER.  Turns out I needed to do a bit of tweaking with the resistor.  The value stated in the article may have worked for some modems, but for my specific one, I had to wire 2 of the 390 ohm resistors in parallel just to get a 8mA current... the articles I read say that the phone company provides 30mA ... and 25mA would have been enough.  but after that, it worked.  I will do a little more adjusting of the resistor if needed later on.

I used a digital multimeter to check the current flowing through the circiuit so you see the leads I used still in the picture.
I had to run minicom (a comm program) to type "ATA" to tell the modem to answer.  After that I quickly exit without hanging up and at the command line type:

pppd /dev/ttyS0 115200 crtscts proxyarp passive

After that.. a peek at /var/log/messages reveals connection successful.  And I can ping the dreamcast's IP.  Another machine on the lan can ping it as well (that's what proxyarp means).  I will be automating this later on... but for now I'll leave it a manual process just to get it running.


Saturday, August 2, 2008

Apple IIGS RGB video to Component converter

There is a fair amount of retro devices that output RGB.  But these were RGB in TV frequencies.  If you try to hook it up to most VGA monitors, they will not sync properly and you would probably get a picture with lots of lines (if you get a picture at all).  The monitors designed for these devices were readily available a few years back, but they are recently becoming more scarce.  Another way of using these signals is using a standard television with a SCART input and a RGB to SCART connector.  Most PAL TV's have SCART inputs (or so I heard).  Having gone through a local TV store recently,  I checked the TV's, both LCD's and CRT's ... somehow they stopped putting SCART connectors on the newer sets and it's been slowly replaced by component input (Y Pb Pr).  Also most NTSC TV's never had the SCART connector.

Well, that aside, another way to view the output of these devices would be to use the standard composite video out to your TV.  So I take my Apple IIGS, hook up the composite out directly to the TV's video in and ...

As you can see, the stuff that are supposed to be in black and white are tinted with color fringes.  This would be somewhat acceptable for games and applications with mostly graphics.  If you are using it with 80 column text, or graphical text, you will soon get a headache from trying to read it.  The Apple IIGS composite video circuits automatically disable the colour burst signal so you get something in black and white.  This improves the readability somewhat but on screens with combined graphics + text you get the same problem.  That is the main reason why the came out with RGB monitors.

Well, my TV has the standard Y Pb Pc component input.  If you connect something meant for RGB to it, it works, everything is as clear as RGB, but with the wrong colours.  That's a good enough start for me.  After searching around for a DIY RGB to component converter, I found one in my local electronics store already packaged as a kit.  It was published as a Silicon Chip article.  I proceeded and assembled the kit.  After that,  I think the TV expects the SYNC signal with the luminance (Y) signal, or it just displays the "no signal" blue background.  

A quick question to Tony Diaz (thanks Tony) gets me what I needed.  It is safe to just tie the composite SYNC signal with the Green output to have "Sync on green".  After wiring a makeshift  D15  IIGS RGB with wires leading directly to the RGB to component converter I finally have the results I was hoping for.  Here's are comparisons of using the composite "video in" image and the "RGB converted" image.  

Last 2 are output of the converter.
The image above is the same TV using the composite "video in".
This one is the same as above, but using the converter.  

Close up of the converted image.  Note the clear black and white text.

Last 3 various images of composite out.
Image of the same screen on converted output

Last 2 are pictures of the Tour of the Apple IIGS.  They are "graphical text".  You should be able to tell which is which ;)

That's the box itself.  Excuse the mess in the background.

Another 2 images for comparison... again you should be able to tell which is which.

More examples

Entire screens.