About

The commodore 64 will always have a sweet spot in my heart. Although not my first computer - that would be an ADAM Coleco - the C64 was the first system on which I really started to develop software in assembler. Now, some 20 years later I still tinker with it and so why not combining a 21st century phenomenon, called social micro-blogging with a 20th century vintage computer!

The C64

The C64 was introduced by Commodore in august 1982, it is 25 years old now. It had astounding graphics and sound capabilities for its time, but if you look at them now they are a bit outdated. The CPU, a 6502 from MOS Technologies, runs at 985Khz, the maximal screen resolution is 320×256 and it has 64KB of RAM.

http://en.wikipedia.org/wiki/Commodore_64

The Ethernet adapter

Even today there is a vibrant scene around the C64. There are even hardware add ons being produced right now. Most add ons take the form of cartridges that plug into the back of the machine. One of these is the MMC replay cartridge that, among others, can add ethernet capabilities to the C64 via a daughter board RR-net.

http://www.c64-wiki.com/index.php/MMC_Replay

The OS

As an underlying OS (yes, an OS that runs on the C64 is possible), I use Contiki. Contiki is an open source, highly portable, multi-tasking operating system for memory-efficient networked embedded systems and wireless sensor networks. More specific, I use their uIP stack to communicate over the Internet with the C64. It is definitely worth looking at. Actually the breadbox64 project grew out of my interest in Contiki to use it as a basis for some real projects later on.

http://www.sics.se/contiki/

The Compiler

CC65 is a Small C compiler or the 6502. The 6502 is the CPU found in the C64 and a lot of other computers of that era, e.g. the Apple ][. It is a complete compiler tool chain with C compiler, assembler, linker and archiver.

http://www.cc65.org/

The result

The welcome screen, ready to log in!

Twittering from a C64

With BREADBOX64 you can post status messages and view your friends timeline. The timeline refreshes every two minutes.  After starting you provide your twitter username and password separated by a colon. After pressing enter, the timeline is retrieved and shown. At the bottom of the screen there is an input field for you to type aq status message. Pressing enter will post that message to twitter.

You can run BREADBOX64 on a C64 emulator. I use VICE, because that one supports networking. However, you can better test it on a real system if you have the hardware ready at hand. If so, copy the D64 to a real disk, put it in your 1541 and go ahead!

If you want to try it yourself, you probably need to find your own ip.cfg file. This is a contiki.cfg file that contains IP, gateway etc. You can generate one overhere: http://cbm8bit.com/contiki/. The one supplied uses 192.168.1.128 as IP and 192.168.1.1 as gateway.

Although primarely programmed for the C64 BREADBOX64 should compile for other systems using Contiki. The only C64 specific code relates to the little bird at the top of the screen, which is actually a sprite.

If you fancy this piece of software, you can follow breadbox64 on twitter! I’ll give some status updates on how this project evolves…

See it run on a C128D in C64 mode.

Download

Download BREADBOX64

breadbox64 source code

My early indoor equipment has two channels. One for the rudder that is bang-bang, meaning it can only deflect full to the left or the right, and one for the motor. A home-brew ESC gives some proportional control over the motor . To make it all look a bit more tidier, I soldered some small connectors to the receiver and ESC board . The advantage of this is that the components can be reused more easily.

I always have been a fan off vintage looking RC planes. So for this season I found two planes I wanted to build and fly with my vintage equipment. One of my favorites is definitely the ‘Guided Mite’. This a design from the fifties meant for rudder only with a small combustion engine. Luckily for me, somebody was kind enough to post the plans to rcgroups.

The other plane is a rogallo wing design, named a cootie. You can find the plans at the fine site of Bob Selman. The rogalla wing is an early design delta wing and has some nice history about it. Also, I just like its retro-look.

After building these two planes, I still had a problem with the transmitter. I still used the transmitter box that came with the BitCar and it was just not good looking. So I decided to do a DIY case for the transmitter. I milled a front panel on my CNC mill out of a piece of white painted wood. After having milled the front plate I applied some red acrylic paint to it and wiped the excess paint away. On the milled parts the paint stuck to the wood, so you get red letters on a white background. Some large keys and a big switch add to the vintage look.

For the guided mite I tried to adhere to the original design as good a I could with the equipment I had. The early RC gear had what was called an escapement. If you take a closer look at the plans for the guided mite you might figure out how it all worked. But basically it was a system that allowed for the next sequence of steering: left-neutral-right-neutral-left-… It was all powered by a wound-up rubber band! So you basically only had a limited number of steering commandos. After receiving an electric pulse, a pin was pulled down by a magnet and allowed the rubber band to unwind a quarter of a turn. The rubber band was connected to a yoke that would in turn drive the rudder.

In my incarnation of this system I used an actuator, basically a coil with a magnet inside of it. This magnet can turn a few degrees left and right under impulse of the magnetic field of the coil. Basically already a bit more advanced than the original equipment, because I just can choose with direction to steer without having to quickly skip the other direction.

The guided-mite ended up with a wingspan of 29cm and a total weight (ready to fly) of 24grams. The Cootie has a wingspan of 33cm and weighs 17grams ready to fly.

I really enjoyed building and  flying these two indoor planes. Don’t ask me why, but I just have a sweet spot for old RC models.

Because I had an old Palm III laying around catching some dust, I thought a bit of googling around Palm and bike computer would not hurt. That is when I discovered Veloace (http://www.engbedded.com/veloace). VeloAce is an Open Source bike computer for PalmOS devices with some very advanced features, like logging distance versus speed, acceleration, trip time and a lot more.

There are different types of cables available to interface an odometer sensor to the Palm. Basically all the sensors use just a reed-switch (http://en.wikipedia.org/wiki/Reed_switch) and a magnet fixed to a spoke in the front wheel. When the magnet passes the switch, it will close and thus give contact. Veloace uses the RTS and RXD pins on the connector, both are part of the RS232 serial communication standard. So, the switch will short RTS and RXD, giving a pulse, when the wheel rotates one full turn, to the software.

As a prototype to mount my PalmIII to my bike, I just connected a PalmIII serial cable to the PalmIII and made a small SUBD9 connector onto which I soldered the correct pins to the wires of the sensor. The Palm III got fixed to the steer by some rubber bands. Although it all worked, this was sub-optimal, too bulky and clumsy and the connector on the PalmIII kept getting loose on jumpy roads. I needed a better solution.

A solution like the original bike computer would be ideal. It is a small device that slides into a fixture on the steer of your bike. If only I could reuse that fixture for my Palm III. Well, that is just what I did.  I took the bike computer apart, which luckily was very cheap at around 3 euros. The lower part of the shell contained the physical connector to the fixture. It has two metal contacts that connect to the wires of the sensor when you slide it into the fixture. I hot-glued this lower shell to the back side of my Palm III.

But before glueing the lower shell I soldered some wires straight on the Palm III interface board and brought them outside via a small hole that gets covered by the lower shell.

Now I can easily insert and remove my Palm III bike computer and just use it as regular bike computer. I hope that the photos below give you enough detail to do it yourself. Happy biking to all!

Demo movie

The small movie was filmed at our local indoor rc group gathering and filmed with my Nokia 5500 GSM, so do not expect any fancy stuff. However, you see the parasail flying along. Although it steers rather easily, you need to be carefull not to end up in a death spiral. Too much deflection of your stick and the paraglider goes down. For me this proves that paragliding is a risky business!

The sail

The sail is made from a light-weight grocery bag and measures 36cm by 12cm. The ribs are made from 2mm depron and have a reflexed airfoil. The airfoil used here is the upper part of the Eppler 184. A total of 10 ribs are placed at 4cm intervals, giving a total span of 36 cm. The reflexed airfoil is choosen for extra longitudenal stability. However, you can argue it is still needed given the very low center of gravity.

The sail is made semi self supporting. It uses ribs to provide the airfoil and a small carbon rod makes sure it does not collapse. At this scale, it will be very hard to make a sail that can sustain its form only by the air captured in pockets.

The lines are made from knitting yarn. The front lines are approximately 40cm long and  the aft ones 43 cm. The angle of attack is approximately set at around 7 to 10 degrees. I should measure it more exactly, but it should be around that number. The angle of attack is rather large, but I had to set it like that because otherwise the paraglider stalls instead of climbs.

Controls

Turning is done by shifting the weight of the puppet. First I tried the biggest actuator I had in my box-o-actuators, but that did not do the job. It was just not powerfull enough and the loose coupling of an actuator was not good for roll/yaw stability. Anyhow, I put in a lightened crystal blue servo of approximately 4 grams - only 2 grams heavier then the actuator - and that just works fine.

Actuator for steering the paramotor had too little power.

When you increase the power, the paramotor climbs, when you decrease power it will sink. When you apply no power, it will go down rather quickly. The reason for this is that the angle of attack is fixed and set at a high negative angle. Full size paramotors have break lines. They can pull down the rear tips of the sail, thus decreasing the angle of attack.

Motor and prop combination

Paramotor prototype after ideal landing.

The powerplant is a motor/prop combination from a salvaged X-Twin plane. They give enough power and only pulls around 500mAh, which is just within the limits what the 50mAh LiPo can give. Flight time with this combination is maximum 5 minutes.

Receiver

The receiver is a MicronInvent minor - one of the best indoor rc receivers around for conventional RF.This is a 35MHz FM receiver, weighs only 2 grams with crystal. Has 5 servo channels or 2 actuator channels and a built-in speed controller.

Full specs

weight: 13 grams
LiPo: 50MAh
Receiver: Minor RX
span: 36cm
chord: 12cm
line length: approx. 40cm
pilot: recycled robocopter pilot
motor: X-Twin
prop: X-Twin

Further reading

• Link to flickr foto shoot
• Another indoor paramotor I discovered
• MicroInvent RX

You can read more about this in my article “Converting a LED cube into an extreme feedback device“.