This is ToneMIDISynth: a MIDI-controlled square wave generator written for the Arduino. The code is available here:
http://arduino.cc/forum/index.php/topic,79326.0.html

I’ve already begun rebuilding this into a full-blown MIDI synthesizer.

Well… the server began powering off after only a few minutes of activity, so I had to crack it open and fix several issues inside.  Self-hosting is great sometimes: the level of control is unmatched, and the costs are low.  On the downside, you must do your own tech support.  When hardware issues crop up, this can be quite an annoyance.  Here’s a shortlist of the issues I worked on.

• Detached heatsink: Almost immediately after opening the case I found the cause of my force poweroffs: the heatsink mounting bracket (already damaged on one side) had broken completely and the heat sink was falling off the CPU. Overheating triggered a safety mechanism that shut down the PC to save the chip. I reattached this using a couple of plastic cable ties from Home Depot. According to BIOS measurements, it is running 5 degrees cooler now than when I originally brought it home.
• Added PCI video card: My aging S3 Virge is now serving VGA duty in the machine. This allowed me to return the 16MB of shared video RAM back to the system. Definitely not much, but with only 384mb RAM total, every byte counts.
• BIOS problems: Made a couple changes to BIOS. Unfortunately, the system remains a bit unstable after power-on… the second hard drive takes a while to report to BIOS after first power on. This generates an error that freezes the BIOS since boot devices had changed. I changed settings to simply ignore all errors and boot no matter what.
• ACPI crash: ACPI support in FreeBSD must have broken at some point recently (or the new gfx card is having troubles with it), but there are kernel panics on boot when trying to run with ACPI enabled. For now I have shut it off with an entry in /boot/loader.conf (hint.acpi.0.disable=”1″). Power management is not really necessary for an always-on server… I have the second hard drive set to spin down after 10mins inactivity, and do not have power to my floppy drive or CD drive at all.

With luck, this will keep me up and running for a good long while.

Just a quick post here before my latest projects all escape me.  I snagged a used PC off Freecycle a couple of weeks back and swapped out my web server – reformatting and installing the latest FreeBSD at the same time, then reinstalling all the ports from scratch.

In fact my needs have simplified considerably since standing up the old server, as I’m now using a TomatoUSB-flashed WRT54GS as my router / gateway instead of the webserver box – meaning I no longer needed dhcpd, natd, an elaborate pf.conf, dyndns client, a second NIC, etc.

Interesting specs: 2.0ghz Celeron (old machine 1.3ghz Pentium4), 384MB SDRAM (old: 128mb RDRAM).  Gigabit ethernet card.  Two SATA ports.  On-board GFX using 16mb shared ram (could put in a PCI card to get that back, if I really need it)  Most everything is up and running as before – a few side projects have dependencies I haven’t reinstalled yet.  In fact the biggest challenge was updating the BIOS, because all my floppy disks are dying… I managed to do it using two half-damaged disks, one for the flasher and one for the ROM, and even then command.com didn’t want to boot so I needed to use the flasher as the interpreter : )

The old machine is going to be fitted into the gutted Galaxian cabinet and run dedicated MAME – win98se stripped, off a CF card.

So I had a few problems I needed to solve:

* My 4 year old daughter loves flashlights, but often forgets to turn them off, and all of our flashlights use D cells or multiple AAs.

* We have a large (20+) collection of “mostly dead” batteries that I feel kind of bad just tossing or recycling

Both these problems are nicely solved by the Joule Thief circuit (http://www.emanator.demon.co.uk/bigclive/joule.htm) – an LED driver that can drain the very last bit of power from a battery and still function for days on end.  It has an additional advantage of only using a few parts, and I happened to have them all on hand… a rarity for me!

I have no idea what the “ferrite” material is.  I stole this massive coil out of a broken car stereo, cracked open the plastic and found that it was actually some sort of tightly wound metal tape.  So I put the plastic back on since it was prone to damage otherwise and just ran a bunch of untwisted cat5e wires around it.  Works great.  The transistor is NPN… I assume the values of pretty much everything here really don’t matter much.  I did have problems getting the lights until I realized I had connected the wrong end of one transformer lead to the battery: the two coils must oppose one another, not run in the same direction.

Of course a bare circuit is fun but not all that useful.  So I stuffed it in a little elephant toy I got off Freecycle and gave him a shiny trunk.  For now the battery is soldered straight to the leads.  One day I’ll get a real AA battery holder and some velcro to finish this up.  In the meantime he’s a good nighttime buddy for my 4 year old daughter.

I’ve posted about this in several other places, so I’m not going to write a lot about it here.  I finished my MAME arcade machine.  It’s a cocktail table style, with a vertically oriented monitor.  It runs DOS and dosmame, and plays 729 games.

There’s a complete build write-up on a separate Google Sites page.  Click here to read it.