DIY calculator: HP30b to WP34S!

Posted: 12/27/2013 6:53:31 PM
dewster

From: Northern NJ, USA

Joined: 2/17/2012

In the not so distant past, engineers - like gunslingers! - had slide rules strapped to their belts, itchy fingers fidgeting nearby, ready to whip it out and calculate at the drop of a hat.  With the advent of IC CPUs scientific calculators replaced them.  Due to their data stack, RPN input, and generally well thought out I/O I've been highly partial to HP calculators, but at some point HP totally dropped the ball and stopped making anything worth buying until fairly recently - I have the newish HP35s which is OK but nothing to write home about.  Enter the HP30b which is a business calculator but with an SDK provided by none other than HP to repurpose the 30MHz 32bit ARM processor inside.  The awesome WP34S project was started:

http://sourceforge.net/projects/wp34s/?source=navbar

http://commerce.hpcalc.org/34s.php

I bought a "new" HP30b off of Amazon.com for $18 (the low price was due to the packaging being a bit beat up, but the calculator itself was pristine).  $6 got me the set of keyboard overlay stickers: http://commerce.hpcalc.org/overlay.php.  The programming cable was the fly in the ointment: Atmel only made a limited run of them and they are apparently all snatched up.  Looking very closely at the various WP34S documents it turns out all you need is a TTL level (3.3V, non-inverted) RS232 interface.  The FTDI chip seems the most compatible (OSes tend to have native USB drivers) so I located and ordered this: http://www.newegg.com/Product/Product.aspx?Item=9SIA2E614S7991 (USB to TTL Serial Cable Adapter FTDI Chipset PL2303HX Cable Computer Cable) for $4 shipped from China (!) and it arrived in the post today.  So $28 bucks total outlay.

Some pix:

The programming cable.  They claim it has TX & RX activity LEDs, but I didn't see anything flashing during the programming process.

Here is the sticker sheet sneaking up on the unsuspecting HP30b.  The key stickers are inside the overlay.  The whole thing is die (CNC?) cut, making removal of the stickers a fairly simple matter.

Getting the background on there straight is a bit hair-raising as you probably only get one shot with the frail framework.  I curled it so the vertical center went on first, then I smoothed it out to the side edges.  I pressed the highly curved sections on the far left and right down with a Q-Tip.  The key stickers then went on one at a time with the help of a tweezers.  If you screw up when placing a key sticker you can take it off and put it back on (ask me how I know this...).  The stickering process took maybe 15 minutes.  Use a good light.

The two coin batteries are actually wired in parallel (the HP30b schematic is included as a PDF in the SDK package), so I just pulled one out to get at +3V and ground.  The then exposed center battery conductor is ground, the rim conductor (located above the center connector, up inside the housing) is +3V.

You have to erase the firmware, then program it with the serial cable.   Erasing is performed by power cycling and resetting the calculator with the lower left serial port hole connected to +3V (there is a small "reset" hole with a switch behind it located directly above the serial port). 

Those are 1k resistors in series with the serial leads to limit current just in case (battery voltage is ~3V, the TTL TX level is ~3.3V).  On the serial port: green=TX (data into the calc), white=RX (data out of the calc), red=+5V (unused for this project), black=ground (common for TX & RX).

Serial programming took all of maybe 10 seconds, and it's not too hard to keep the connections steady for that long, even hand-held as in the picture.  If you botch the programming just start over, I don't think there is much - if any - risk of bricking it.  Don't leave the batteries in it unprogrammed, otherwise they might get quickly drained.

Post programming, showing the new firmware version (h, 3, 3, ENTER).  Woo hoo, back in business!

Long live the open source movement!

Posted: 12/28/2013 2:52:40 AM
FredM

From: Eastleigh, Hampshire, U.K. ................................... Fred Mundell. ................................... Electronics Engineer. (Primarily Analogue) .. CV Synths 1974-1980 .. Theremin developer 2007 to present .. soon to be Developing / Trading as WaveCrafter.com . ...................................

Joined: 12/7/2007

Hmmmm.. Looks like fun! ;-)

But you still need an HP to start with...

I just got myself a new calculator, or 2, or 250... LOL ;-)

For Xmas I bought four reconditioned Android tablets - these were returns re-boxed and with full warranty etc - I managed to haggle the price down (they had 4, and it was the last day before Xmas, so I bought the lot, with keyboard "wallets" for £120 - the RRP is £120 each ;-)

So now each of my children have their own computers, And I have one..

I have never even played with anything Android before - and I am blown away by it - Software is so cheap! (often free).. It came with an Office Pro clone, and I have spent about £20 and got electronics design and simulation packages, maths courses with embedded calculators / worksheets from the developers of Mathcad, loads of free design data / tools etc from manufacturers like ON and TI - and some HP RPN scientific calculators.. But, to be honest, there are multi-function programmable graphing calculators which IMO beat the old stuff hands down --- The ability to scroll the screen with a swipe and select whatever functions / constants / operators etc you wish, and on one I can even create a calculator with whatever I want.. Scientific, Engineering, Graphing..

I think my days of 'dedicated' hardware calculators are over - Oh, sometimes something about their "feel" will probably cause me to have nostalgic feelings - the way slide-rules still do..

Oh, it does look beautiful though - I fully understand the reason for doing the conversion - just looking at the pictures makes me want one!  ;-)

But my £30 7" Android tablet is, I think, probably as important an event for me as when I got my first  scientific calculator and put my slide rule away.. Maths appliances have been of utmost importance to me, as without them I am so slow its useless  - My 9 year old son can do mental sums twice as fast as I can, and is now manipulating algebra at about the level I can manage, and beating me at chess... ;-) .. Its one of my greatest joys knowing my children are way brighter than I am!

Fred.

 

Posted: 12/28/2013 9:56:13 PM
dewster

From: Northern NJ, USA

Joined: 2/17/2012

"I think my days of 'dedicated' hardware calculators are over - Oh, sometimes something about their "feel" will probably cause me to have nostalgic feelings - the way slide-rules still do..

Oh, it does look beautiful though - I fully understand the reason for doing the conversion - just looking at the pictures makes me want one!  ;-)

But my £30 7" Android tablet is, I think, probably as important an event for me as when I got my first  scientific calculator and put my slide rule away.. Maths appliances have been of utmost importance to me, as without them I am so slow its useless..."  - FredM

Glad you're digging your Android tablets Fred!  I'll have to give one a try soon.

For me, data input via some kind of tactile input for the math device I'm using is pretty mandatory.  I don't want to have to check every number I enter because that's tedious.  HP keys (front hinge with the click dome underneath) are pretty responsive.  I don't think a touchscreen interface could completely fill the bill for me.

But, yes, calculators are something of an anachronism.  It would have been nice if the computing middle ground (PDAs or similar) had worked out a little better and a little earlier.  Laptops are overkill at times, particularly when you just want to sit and think with your notebook.  A 3D monitor with a chordal keyboard would be neat, perhaps in a binocular form factor.

One of the reasons I wanted to design a processor was to get a better handle on the lower level, but designing a personal computing device from the ground up is a daunting task (a dream I hope to see come true one day).1 and 2 stack processors & languages aren't yielding the magic I'd hoped for (Hive is now up to 8 stacks) so even the WP34S project isn't fully what I'm searching for.  They need to take it to the next level rather than largely just replicate the past.

Posted: 12/28/2013 10:34:51 PM
FredM

From: Eastleigh, Hampshire, U.K. ................................... Fred Mundell. ................................... Electronics Engineer. (Primarily Analogue) .. CV Synths 1974-1980 .. Theremin developer 2007 to present .. soon to be Developing / Trading as WaveCrafter.com . ...................................

Joined: 12/7/2007

"For me, data input via some kind of tactile input for the math device I'm using is pretty mandatory." - Dewster

I thought it was for me - and I would still far prefer tactile feedback..

Which makes me think there is a potential product here.. A transparent tactile overlay for capacitive screens - one could have some silicon polymer with a click action, and the legend could be seen through the overlay - one could then configure the screen tor whatever type of functions one wants, and still maintain the 'wiping' function on the display area.. With some of my Android calculators one can 'flip pages' to get mor or different functions, and this is a major improvement on trying to cram multiple functions into a single fixed keypad..

In reality though, I am getting used to the non-tactile interface.. I think the page-flipping helps because the "buttons" are large (on a 7" tablet) - one does not require "shift" or whatever -  I have no problem with entering data.

Fred.

Posted: 12/28/2013 11:57:22 PM
Thierry

From: Colmar, France

Joined: 12/31/2007

I have also a "true" HP-35S and a HP-41CX emulation on iPhone and iPad. But if I need quick results, I'm still better with my Faber-Castell NOVO-Duplex 2/83N slide rule...

Posted: 12/29/2013 12:39:08 AM
RoyP

From: Scotland

Joined: 9/27/2012

My first calculator was a Sinclair Scientific with RPN-don't quite know why but my fellow classmates at school couldn't get their heads around it.

Anyhew, several/many years later and I now have an android tablet with a calculator app installed on it: I'm a simple kind of guy and the only criteria it had to meet was to be scientific, have a dedicated pi button AND a RECIPROCAL button.

Posted: 12/29/2013 1:23:49 PM
dewster

From: Northern NJ, USA

Joined: 2/17/2012

"I have also a "true" HP-35S..."  - Thierry

The thing about the 35S is it's tantalizingly close, but misses by a mile.  The hex and binary modes are so awkward I don't use them even though I really want/need to.  Store is a shifted function which is strange.  X<>Y exchange and roll are hiding in up in the function buttons, and the arrow key pad feels tacked on.  It also doesn't insert commas as you key in a number, which forces me to count the zeros of large numbers before I hit the ENTER key.  I kind of like the clamshell case though (<=damning with faint praise).

Posted: 12/29/2013 8:21:54 PM
dewster

From: Northern NJ, USA

Joined: 2/17/2012

HP30b to WP34S Part Deux : The Xtaling

OK, "Geoff Quickfall" over at the HP museum fora put a bug in my ear to add the xtal.  I just changed our crappy electronic house thermostats with the good old fashioned mechanical types, so there was a convenient crystal and caps just sitting around waiting to be repurposed.

First you undo all 5 screws indicated here in red, two of them are behind the bottom rubber foot.

Then you figure out a way to snap the damn thing apart without killing it or marking it up too much.  I used pieces of one of those wooden shims you use to hang doors and such, sanded smooth and thinner on the business end.  Worked from the right, up around the top, down the left, and finally the bottom.  Kind of harrowing with all the flexing and stuff going on, the snap closures are way too beefy and numerous.  Snapping it back together is kind of scary too.

Pads indicated in red.  Add some solder and stick your xtal and two caps on there.

Here they are installed - this is NOT my best work!  I shouldn't have pre-soldered the cap pads.

Reflashed it and now it's got a real-time clock and calendar - Woo Hoo!  I wish there was an option to show the time and date all the time.

[EDIT] I should have mentioned: for the xtal mod I used this document http://sourceforge.net/p/wp34s/code/3366/tree/doc/How_to_install_crystal_and_IR_diode.pdf as a reference.

Posted: 12/29/2013 9:03:07 PM
FredM

From: Eastleigh, Hampshire, U.K. ................................... Fred Mundell. ................................... Electronics Engineer. (Primarily Analogue) .. CV Synths 1974-1980 .. Theremin developer 2007 to present .. soon to be Developing / Trading as WaveCrafter.com . ...................................

Joined: 12/7/2007

Impressive stuff, Dewster - And yeah, the Sinclair Scientific was my first Sci calculator as well ;-) (I met Clive a couple of times - was going to work on his next "C" vehicle about 10 years ago, but the project was dropped)

I am fighting hard to stop myself getting distracted into the Android.. There's a voice to text feature I now use extensively (want to visit TW, just talk to my tablet and the browser loads up and takes me here.. ;-) .. Next would be to get my calculators to take voice commands - no problem for numbers, but Id need to get into the system to get functions etc..

NO! - I really dont do enough maths to justify the diversion...............

 

Posted: 12/30/2013 10:06:57 PM
dewster

From: Northern NJ, USA

Joined: 2/17/2012

Set the time yesterday, just checked it now and it seems to be hanging in there.

"I met Clive a couple of times - was going to work on his next "C" vehicle about 10 years ago, but the project was dropped"  - FredM

Wow!

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