July 17, 2009

Halfway status report. Display - success

My computer is becoming wearable, though it's taking some time.

Half of the allocated time is gone already, and I feel like I should have accomplished a lot more. Also I feel like I'll be finished in a week, which is not true either. I now have a working computer, which doesn't yet seem to understand my 3g, working head mounted display, in monochrome as it's a lot more readable that way and I'm going to spend my time in command line anyway, and barebones keyboard, which has not yet been programmed because of missing atmega8 programmerthingy.

 My achievement this week has definitely been the display. I have bought a lot of cables and adapters. The Beagleboard gives S-video and Myvu Crystal wants S-video or composite, but it accepts a 4 conductor 3.5mm plug. Currently I have a modified S-video to RCA -> RCA to 3.5mm plug, but a while ago I had like four or five adapters and cables going around. That thing didn't "just work" and everything was a lot better after I had replaced the wiring. I did try to mess with the os settings for overlays, displays and framebuffers without enough knowledge, but the problem was with my cables. There was also the thing that first I didn't get any signal at all before Gregor Richards helped me a bit. There's just so much conflicting and old information, and not enough new information about s-video on Beagleboard+Ångstrom. I'll also have to thank a fellow student who has been helping me with some information and other things.

 I still need to modify them though. Myvu Crystal is a weird thing, as the usb-charging cable works as a ground, and so I shouldn't have another ground going to Beagleboard, because that messes the signal up. I already cut the ground pins there, but wasn't enough. Currently I get best signal if I leave those RCA cables hanging so that their grounds don't touch each other and I use the white RCA of the a/v jack and just touch the first metal thing on the Myvu pendant with the tip of the 3.5mm plug. If I use the red one and just stick the 3.5mm plug in, it gets worse signal. Probably because there's also sound signals going there. I need to break the plug so, that there is just the last tip that can connect to anything.

It's been irritating to look at micro sized flashing ntsc screen, but now it is perfectly readable and the signal is just perfect. After I've fixed the cables, I'll just need to break the myvu and put one of the displays inside some sunglasses I'll be buying soon. I'll also need that stupid half-silvered/see-through mirror which will be in front of my eye and which will allow me to see through the display. Then the display is done.

It could have been a lot easier and better, and still might be, if I'd just buy the correct driver chip from Kopin. It's "just" 50$ and the correct is that version where I could bypass the composite and just feed it a pure digital display (I've been told that myvu pendant has the driver board version that has some stupid chip which you can't see it's pins so no wiring there). That way I could have used the dvi-d signal of Beagleboard and everything would be lollipops and rainbows. They still are, but they would be the colored things that way. There are some nice specifications at Kopin webpage. For your information, Myvu Crystal uses Kopin 640x480 microdisplays. Driver board might, or might not be Kopin, but it has the same chips that handles the signals and probably the same decoder for composite/s-video signals. 

 I'll be getting the chip for the keyboard (Spiffchorder) soon, but I'll need to rewire the keys and craft a handle for it. I'll try making one from finfoam. Then the keyboard is also done, if it can type scandinavian letters like ö and such. If not, I might need to touch their code too.

My computer needs wvdial or something similar, so it could use my 3g. It also needs a box, maybe from finfoam. Maybe I should make the box from some clear plastic though. I have ordered a usb ethernet card just because I'll probably need it sometimes. I'll need to decipher why narcissus, the awesome Ångstrom distribution image builder gives me enlightenment and gnome-games and such, when I clearly order a command-line only setup. I don't know what I should kill to get to command-line now. Alt+ctrl+F1 doesn't work, though it clearly has worked sometimes for some unfathomable reason. If I just kill enlightenment, xorg and/or gpe-login, they will just restart. I should study my chosen distribution a bit more.

And finally, I'll need a battery. I'm thinking about those rechargable batteries, I've seen some high mah ones that should do with some kind of a 5V regulator.

 I'm trying to do most of the keyboard this weekend, then I'll check the software I'll be using and the cables. I need some new, short cables, It's been a joke of the day that I could use them as my only clothing. It also seems that being mobile doesn't mean not having lots of wires around. After my keyboard is finished, I'll build the computer case and the sunglasses-display, and afterwards, I'll make the battery and start wearing the thing when I'll manage to find a way to wear them. Maybe I could just hang the computer from my belt. I definitely don't want a fannypack or a backpack. Maybe something like the Casebelt from Urban tools. Do you know some nice way for wearing the wearable? Comments welcome.

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