Re: Electronics Projects and PC Interfacing

[Tim McDonough <tmcdonough@gmail.com>]

Matthew Kotys wrote:
> Does anybody here have experience with electronics design, and 
> interfacing USB / Serial / Parallel ports on Linux hosts?  My intent is 
> to mess around with controlling DC/stepper motors, temperature sensors, 
> maybe a USB <--> IR adapter for TV remotes.  I have done a few "Hello 
> World" projects on PIC uCs, but I'm sort of bored with blinking lights 
> in succession and triggering a piezo buzzer.  I have a basic 
> understanding of DC circuits, but I'm not so good at peripherals and 
> drivers.  I use C, Perl, Python, PHP, bash scripting all the time...

The easiest way to work on "one of a kind" items (vs large volume 
production) is to get an Arduino Duemilanove single board computer. 
<http://arduino.cc/>. They are available from several US suppliers, I'd 
recommend Sparkfun Electronics <http://www.sparkfun.com> as they will 
also have a variety of sensors that may intrigue you.

The Arduino environment includes GCC tools for C/C++ and an extensive 
library that lets you easily use the peripherals like digital and analog 
I/O that are on the board. It is available free of charge for Windows, 
Linux, and Macintosh platforms. Once you get bored with USB the Arduino 
supports WiFi and Ethernet modules as well. There are tutorials on the 
Arduino site for using all sorts of sensors, stepper motors, etc.

> Maybe I would start like this:
> 
> project 1: build a USB morse code receiver, translating to text as it 
> takes in user input
> The translation software for this would be interesting to write
> 
> project 2: build a USB morse code/ transceiver/, allowing for tty 
> sessions entirely in morse - (funny)
> 
> project 3: rip out an LCD from an old calculator, connect it to a 
> keyboard and a breadboard, and run a serial (or USB) cable across the 
> room from my PC.  So, an actual (and really dumb) tty

Morse generation is pretty straight forward. Receive and decode not so 
much.

No matter how good it is sent there are many variations in Morse sent by 
a human that the brain and the ear automatically compensate for. The 
length of the elements (dots and dash) varies, the inner element spacing 
variaes, the character spacing varies, the word spacing varies, and the 
overall throughput/speed varies. Once all that is accounted for you need 
to filter out noise that looks like dots and dashes, signals that fade 
up and down due to atmospheric conditions, etc.

Tim (call sign N9PUZ)

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