[chbot] Cool gadget of the week. (For those who didn't see my miss-post on the Linux list!)

[Chris Hellyar]

OK, you can tell I'm on holiday, time on my hands and all that.

Microchip Application note AN689 'Engineering Assistant'.

http://ww1.microchip.com/downloads/en/AppNotes/00689a.pdf

I built one yesterday, using a PIC16F628 (Didn't have any F84's) and
removed the code, and hardware for the battery support.  A very cool
little bit of bench test gear out of an old 2x20 LCD and a handful of
junk-box bits.

In a nutshell:
- A high/low/pulse logic probe (pulse detect down to 10ns)
- 40Mhz Frequency counter
- Single channel sort-of 'logic analyser' up to 1Mhz capture
- Async data capture/view at 1200-115k baud.

The chap who designed it it is an interesting fellow as well:

http://en.wikipedia.org/wiki/Voja_Antoni%C4%87

(The wikipedia even mentions the gadget, and there is a link to a site
dedicated to it: http://www.qsl.net/la9sja/electronics/ea/)

When finished the design requires all but 1 word of program memory, and
almost all of the eeprom space to function, the circuit is worth
studying as an example of how to get the most out of a chip, as is the
code, even if you don't build it.

With a small amount of fiddling it'll work in any pic that does 10Mhz,
and has the same or more memory than a 16F84.  I used the 628 as I had
one in the bits box, the only change to the code I made was to replace
the eeprom lookup with a 'dt' table (It didn't function on the 628, not
sure why) and to comment out the bits for battery/power control. I also
removed 90% of the discrete from the circuit as that is for the
battery/power management.

If anyone is interested I'll take some snap-shots of the thing working
and post them as well..  This might be old hat but I thought it was
worth sharing as it's a lot of functionality for very little time and
money invested, and lets face it, we can always use more test gear!

Have a good weekend.