nikosapi's ramblings

I've been making a bunch of breakout boards recently using the toner transfer method. I think I've finally nailed the procedure such that I get good, repeatable results. The following wiki article only explains how to do the transfer, generating the layout and etching is pretty straightforward (links are provided to some good guides). I've been using gEDA's "pcb" software to layout the board and a cheap bottle of ferric chloride for etching.

Here's a link to the article: Making Printed Circuit Boards Using the Toner Transfer Method

I've recently been tinkering with TI's MSP430 line of 16bit microcontrollers thanks to the crazy-cheap MSP430 Launchpad development board. For less than $5 you get a USB programmer, an in-circuit debugger (that works with GDB!), and a USB to serial converter. There's pretty decent Linux support for these chips, much like with Atmel's AVRs you have a GCC port (msp430-gcc) and software to program the chips (mspdebug, which also doubles  the in circuit debugger and GDB proxy). Overall, I'd say I like MSP430 better than AVR. The documentation is better (although there's much less user-generated content/code), the header files make more sense (register names stay the same between chips, and there's no 1<<PB4 nonsense, bits are actually defined as bits, not shift increments), and most importantly, the development environment is cheap and not at all intimidating (ie. I didn't have to build my own programmer).

Anyway, gloating about the MSP430 wasn't the purpose of this post, it's about a simple HD44780 driver library I wrote for use with MSP430 microcontrollers. The library is written such that at a clock frequency of 16MHz, the display will be written to as fast as possible (with respect to the timing requirements set forth in the datasheet). The example compiles down to roughly 450 bytes which isn't too bad, if you manage to cut it down, let me know

All the information you need is available on the wiki.

For the past couple weeks I've been working on adding an auxiliary input to my car's stock head unit. Mazda didn't make it easy but in the end I think I have a nice solution that works pretty well.

What you see above is a little board that pretends to be a tape deck in order to trick the head unit into opening up the tape deck's audio inputs. It also is capable of interpreting commands from the radio and sending them to an iPod which makes changing songs on the road a lot easier and safer.

I titled this post "More Information Than You Require" because I put up a series of pages on the wiki completely documenting the protocol used by the head unit as well as schematics and source code so you too can build a tape deck emulator.

• Link to the "Mazda Entertainment System" wiki articles

For the longest time I've been using an old CRT television as my alarm clock. It was very simple, there was a sub-menu in the TV's setup menu that allowed you to set a time for the television to turn on. This worked great for many years until I got rid of the TV. I tried using a radio like a normal person but the television is far more effective. It combines light, sound, annoying commercials and terrible programming which gets me out of bed in no time.

So what's an average Linux user to do?

Turn an old laptop into a TV of course! With the help of XBMC installed on the laptop and my trusty MythTV backend I had everything I needed to make an IPTV. The laptop is an old Toshiba with an Intel Celeron processor, 768MB of ram and an Intel 915GM graphics card. It surprisingly runs XBMC pretty well at the screen's native resolution of 1280x800. This is great, now I have a TV again with all the added benefits of MythTV's PVR capabilities. Although, this still doesn't solve my alarm clock problem...

Or does it?

It turns out that there's a very simple way to get XBMC to play a live channel from MythTV. The following bash script does just that:

#!/bin/bash
 
XBMC="xbmcbox2:8080"
MYTHTV="USERNAME:PASSWORD@mythbackend1"
MYTHTV_CHANNEL="906"
VOLUME="60"
 
function xbmc_command(){
  wget -q http://"$XBMC"/xbmcCmds/xbmcHttp?command="$1" -O /dev/null
}
 
xbmc_command "SetVolume($VOLUME)"
 
MYTHFILE=myth://"$MYTHTV"/channels/"$MYTHTV_CHANNEL".ts
xbmc_command "PlayFile($MYTHFILE)"

Note: "xbmcbox2" and "mythbackend1" are hostnames, replace with whatever you're using (like IP addresses or your own custom hostnames).

By running the following script on any computer in your network the computer running XBMC (pointed to by the XBMC variable) will start streaming the channel you specified (by setting the MYTHTV_CHANNEL variable). It also sets the volume to an appropriate level in case I left it too high/low the night before. This script can be added to a crontab or to your favorite alarm clock program (like Kalarm or Alarm Clock).

In order for the script to work the computer running XBMC must be allowed to stream from the MythTV backend and XBMC must be configured to allow remote HTTP connections without a password (this could be fixed by using wget's --user and --password options).

For most people the overlay adapter is a better choice than the textured video adaptor because you can use it with compiz and it doesn't have horizontal tearing on fast action scenes. The disadvantage, as pointed out by someone in #gstreamer is reduced color accuracy (iirc) but I don't notice it...

If you have an Intel graphics card that's capable of using the Xv overlay adaptor here's how to enable it (for gstreamer):

Run "gstreamer-properties" (using Alt+F2)

Use the following settings

For mplayer, find the port base of the overlay adaptor:

[nikosapi@localhost ~]$ xvinfo | grep -A2 "Video Overlay"
Adaptor #1: "Intel(R) Video Overlay"
number of ports: 1
port base: 81

Then add "vo = xv:port=81" (change 81 to whatever your port base is) to the [default] section of your ~/.mplayer/config. This is what my config file contains:

[default]
vo = xv:port=81

This assumes you have tor and privoxy installed (and privoxy is accepting connections on port 8118).

rtorrent \
-i `curl whatismyip.org 2>/dev/null` \
-O encryption=require,require_RC4 \
-O http_proxy=127.0.0.1:8118

It's that easy

UPDATE: You may need to disable DHT for this to work, add "-O dht=disable" to the command line or simply put "dht=disable" in your ~/.rtorrent.rc

Today I finally got around to moving this website to a proper webserver with a ton of bandwidth

If you find any dead links/broken pages please contact me, I'll make sure they get fixed ASAP.