View Full Version : Homebrew, hand-built, and I didn't have to wait for a pcb.

Peter Jakacki
07-14-2009, 06:28 PM
Amongst the many things I don't normally do is hand build a prototype on matrix board, at least these days. Ok, so I cheat a little and use my various pcb modules.

Because I decided to use this small box with a clear lid I ran out of depth for my 20x4 backlit lcd with one of my serial backpacks. So I looked at just wiring the display straight into the prop module but I hate wires so I modified my backpack so that it is flush with the lcd and nothing extends further than less than a millimetre. So now it all fits and I just need to print out a front panel label to dress it up and then test it out properly.

Once I check it out properly I will finalize the pcb so I know it will fit.

Can you guess what it is?


07-14-2009, 06:54 PM
World's first Propeller based calculator?

Nick Mueller
07-14-2009, 07:01 PM
> Can you guess what it is?

Finally! A replacement for the HP16C that was stolen from me long time ago. :-(


Never use force, just go for a bigger hammer!

The DIY Digital-Readout for mills, lathes etc.:
YADRO (http://www.yadro.de)

07-14-2009, 08:39 PM
A security code entry system?

I'd really like to know how you interfaced the USB numeric keypad to the prop!


Peter Jakacki
07-14-2009, 08:48 PM
HP16C !, man that brings back some memories. I "lent" mine to a friend who moved away which was the last I saw of it.

But nah, it's not that. The SD card module should give you a bit of an idea though. I'm also using the indicator leds as buttons but the main entry is via the keypad. The LCD shows up some large digits at times and the blank area of the board is for some retasking so I could test it for another project as well.

The other project is actually for my test bench as a multimeter or more correctly, a MultiCoreMeter. I'm sick of reading 3V when something's floating and the awkwardness of a standard meter. So I want a nice clear display that automatically measures the source resistance of the signal along with many other parameters. Automatically if it doesn't detect a voltage it will assume it needs to measure resistance or capacitance etc along with continuity. Of course I have the option of plugging in a TV and also recording all this to the SD card or communicate with a PC. I will probably use scope type leads with this. Initial ADC will be 18-bits along with some input switching but I am only trying to test 48V or less.

A DAC feeding a comparator on the input side will allow me to extract the frequency of the signal so I can also display these parameters. Along with Chip's speech synth I might be able to make it tell me what's happening without having to look up.

Still haven't guessed what this version is though.


07-14-2009, 08:51 PM
Actually, that may be the second. I built the maybe first Propeller calculator last year. It has built-in keyboard and graphic display... and needs some software besides math routines http://forums.parallax.com/images/smilies/smile.gif

Edit: But to be fair, mine does not work, well the keyboard does not work because I forgot some diodes :-(, and the power supply for the LCD bias does not work either :-(.

Visit the home of pPropQL: propeller.wikispaces.com/pPropQL (http://propeller.wikispaces.com/pPropQL)
pPropQL020: propeller.wikispaces.com/pPropQL (http://propeller.wikispaces.com/pPropQL)
OMU for the pPropQL/020 propeller.wikispaces.com/OMU (http://propeller.wikispaces.com/OMU)

Post Edited (Ale) : 7/14/2009 1:59:17 PM GMT

07-14-2009, 09:24 PM
I think I still have a few serial keypads (beige) that are like the one in the first post. If anyone wants to build a similar unit I can see if I can find them. Just send me a PM if you are interested in one.


07-14-2009, 10:07 PM
to Painless

Actually, there are lots of keyboard's controllers, which supports both USB and PS/2 standards. I think, it is plugged here as an ordinary PS/2 device.

07-15-2009, 01:06 AM
Cool Peter.

what's the funky looking cable with the blue tape around it - a heat-shrunk prop-plug?

- H


Peter Jakacki
07-15-2009, 12:00 PM
Ok, the keypad is a dual USB and PS/2 so there is no point in trying to use the PS/2 adaptors that come with it. However it also allows me to test out some USB code on pure USB keypads if I want. The white and blue cable is my PropLink cable which uses an extra row of pins above the standard four to allow power and I2C to be connected. This permits powering the device from the USB and also direct access to the EEPROM if necessary.

What is this? No, it's not a calculator or anything like that. I have made up a wave file player before but this one has a dual purpose plus I wanted to use OTS keypads and compact and clear display. Once I print up some polyester labels on the color laser it will look the part. I can cue up tracks directly and playlist them plus I have more control over positioning in long talks. Standard MP3 players are all menu driven and slow and awkward to operate. When it comes to playing a song or sound on cue then this unit is very fast, instant even.