PDA

View Full Version : Fun with TI-74s - Hamming codes



JGardner
August 4th, 2014, 07:08 PM
Error-correcting codes are a fascinating subject, despite the occasional tendency

for eyes to cross while enjoying their mathematical derivations... :)

Richard Hamming also later gave us two classics, "Numerical Methods For Scientists

And Engineers", and "Digital Filters" - By all means; don't deprive yourself...

But anyway -

Hamming codes are something I've been aware of for many years, without an

excuse to indulge; this changed recently - As a first step to getting up to speed I

thought I'd try a TI-74 BASIC demo implementation.

Easier said than done, it turned out, but it seems to work. (If you find differently,

I'd like to hear of it...)


errors noted -

1) terminology; code is Hamming 12,8, not 8,4 ...

b) pseudo-random byte (0-255) generator should be: INT(RND*INT(256+.5)+1)-1

JGardner
August 15th, 2014, 06:35 AM
A Hamming 8,4 example...

Enter a nybble at the prompt. Pgm displays the entry on binary format, then

expands the nybble to Hamming format and displays it. Press [ENTER] .

The Hamming formatted byte is then displayed - The blinking cursor prompts

for a 1 or 2 bit change.* The algorithm processes the entry appropriately and

displays the result.


* The result of changing more than 2 bits is an undetected error.