Half-Byte » Project

Old School Bluetooth Handset

nibble — Mon, 08 Mar 2010 19:44:11 +0000

I had a little fun and threw together something I always wanted to do.

Back in the day, we used these massive handsets with our land line telephones. They had just the right amount of heft and a design that allows you to ’shoulder’ the handset. You can still find them in hotels and attached to payphones.

Today our cellphones are tiny, light, and too slim to shoulder. So, with a nostalgic wisp I decided to pack a cell phone into the handset of an old rotary telephone.

It was a short build and I ended up packing a bluetooth ear piece into the enclosure instead of a full, outright wireless mobile phone. This way, there’s no need to get a separate phone account or swap out SIM cards.

The build was basic. I simply cracked open the bluetooth headset, saw what was inside, and did some simple soldering to extend the wires for the ear speaker and surprisingly tiny microphone. I also soldered a header connection on the microphone wire since it would be useful to disconnect the device from the handset without having to re-thread everything.

After packing everything up, it worked like a charm. However, it was lacking one important element; the proper weight. Since the old massive mouthpiece microphone and old ear speaker were tossed aside, the balance and heft were off.

I wandered around my home looking for good ballast and turned up a handful of pennies. These were stuffed into the handset, along with some packing foam to keep the electronics and coins from jingling. Once that was done, I had a blast chatting away on my new cell phone ‘handset’.

After mentioning this project to a friend, he explained how he pictured me with the handset driving down the road. “That’s not gonna work. It would be illegal in California.” So, we both chuckled and explained how it could be strapped to my head with a sweat band. With that image in mind, I couldn’t help but envision being pulled over by a policeman with it stuck to my head and saying with a wink, “What seems to be the problem officer?”

New Charge Station for the New Decade

nibble — Thu, 07 Jan 2010 20:54:04 +0000

I used the Charge Station I built for a while, but the appearance started to annoy me. Why would I want to have a plastic tupperware box sitting out in my living room, especially when the duct tape was visible through the frosted top? The box was too sloppy so I made another attempt at it.

This time I spent the following (Total $7.50):

Tiny surge protector from Daiso: $1.50
Three wooden trays from Daiso: 3 x $1.50 = $4.50
Hinges from Daiso: $1.50
Elmer’s Glue: practically free…

The power adapter was cheap, so I felt free to disassemble it to fit it through the tray handle; the power plug wouldn’t fit otherwise. This was straight forward since the power adapter had regular Phillips screws.

I needed to use a razor to cut out the bottom of one tray to make more space for the power adapters. This was a little tedious and probably the most difficult part. But, otherwise this project was simple, fun, and quick. It only took about an hour to complete.

Bricking an ATTiny2313 and getting LED’s to flicker with a 12MHz external clock

nibble — Mon, 30 Jun 2008 08:32:46 +0000

A while ago I was doing some mindless fiddling with project’s makefiles and happened upon some fuse code. I gave it a shot and immediately found it to have destroyed my ATTiny2313 chip; “bricked” it if you will. A few more attempts at trying restore the fuse bytes failed and even reading the signature of the chip failed. It appeared as though I wiped the chip. I got a little worried after looking over my inventory of hardware and only found one more AVR microprocessor. So, I sent off another order with Mouser Electronics for a batch of spares. They got the mailing and billing addresses mixed up, but I forgive them since they aren’t far from where I grew up.

I then spent some time with a very basic circuit and code just trying to get my bearings with the toolchain. It is basically an ATTiny2313 hooked up to a USB cable for power (@5V) and a couple of LED’s and resistors. The LED’s alternate blinking to indicate the clock speed. Figuring out how to code a delay was a bit of a hassle, since I was working with pre-existing code for the USBTinyISP and it was using a variable that was initialized by data received over the bus. I ended up using a simple loop to delay the LED state change.

Since I’m hoping to mess with USB, I need to get my microprocessor running at 12MHz. So, I did some more in depth research on clock sources and decided to make an attempt at using an external 12MHz ceramic resonator clock. The ATTiny2313 by default runs at 8MHz with the internal clock. So, changing it requires mucking with the fuse bytes, which I already had a negative experience with before. This time I was a little more informed an careful. I used this AVR Fuse Calculator web page and made the bare minimum changes necessary. The default low and high fuse bytes for the ATTiny2313 are: 0×64 0xDF. Since the external clock only requires the low byte to change I ended up using: 0xEF. Here’s the command line:
> avrdude -c usbtiny -pt2313 -U lfuse:w:0xef:m

Before running the above command I took out the 3 pronged ceramic resonator (3 pronged because it has the capacitors included in its housing). I didn’t want any more variables affecting my fusing. Also, I recommend you read the fuse bytes before writing them. You may want to write it down just in case you decide you want to return the chip back to the initial state. Immediately after running the command, the LED’s stopped blinking and it looked like I busted it. But I knew better. Once the resonator was plugged into the proto board, the LED light up again, and with a break neck pace… 50 percent quicker.

This was pretty damn cool. Doing these simple projects are small steps to getting to where I want to be. In the process I’ve been able to learn the basics of programming an AVR chip. Even now, I think I can plug my previous “bricked” chip in with an external clock and get it to work. The microprocessor is just waiting for a clock source to tell it to drive. So, an “un-broken” chip is icing on top of what I’ve learned.

DIY: Charge Station for your Electronic Devices

nibble — Thu, 08 May 2008 06:06:04 +0000

A while ago I saw an article on Lifehacker about building your own charge station to reduce clutter of adapter wires. The idea stuck in my head, because I often collect a nest of wires at the floor of my desk. These wires often find themselves becoming tangled around the wheels of my chair causing more headaches over my already cramped office situation. So, I began a little investigation and found the following:

Total cost: $5.50 (+tax)

Simple surge protector from Fry’s: $3.00
Simple “tupperware” box (20×13x12 cm) from Daiso: $1.50
T shape 3 plug power adapter from a local hardware store: $2.00

To build it, you basically cut a hole in the side of the box and jam the surge protector inside. Then you plug in your adapters and the “T” shaped plug (orange in the picture) and cut a hole where it touches the side. This allows you to attach another adapter to the side of the box without needing to open the top and shift around the plug configuration. Then you cut holes in the top and feed the ends of the cables through them. A little duct tape will keep the wires from slipping back into the box in inadvertently.

If you keep the switch on the outside of the box, this allows you to turn off all the current to the adapter, which will help reduce wasted electricity. Those adapters do use up some juice, even when they aren’t charging anything! The only gotcha about my power station is that I bought a surge protector with a cheap switch. There is no LED in the switch, so you can’t tell if it is on or off. If I were to do this again, I would shell out the extra 2 bucks to get a surge protector with a lighted switch.