What's your de-facto calculator?


Hi all.

As I've recently acquired my new toys, I've developed a particular routine. Since my 55 has pretty much everything I need for RPN calculations, I've been finding myself grabbing that one for my rudimentary number fiddling. As I usually leave the program development and robust calculations to my think-tank--my 15C, 32SII, 42S, 67, 41CV and so forth, my 55's becoming my day-to-day low impact number fiddler.

So, what's your day-to-day calculator?

Edited: 5 Apr 2012, 3:03 p.m.


My response is, as always, the one I am creating right now. :-)


Edited: 5 Apr 2012, 3:18 p.m.


I concur :-) Maybe not the same as Tim's ;-)


heehee - that's right, we're using the one that Tim thought was finished :-)


Hope all is well.



Tim wrote:

My response is, as always, the one I am creating right now. :-)

Same here! In my case, a DIY4X, still working toward a new DIY5 model.

I'm in the midst of completely rewriting the keyboard handling. That necessitated a complete rewrite of the timer management, which in turn caused me to write a general-purpose doubly-linked-list library to manage the timers.[*]

Previously I used a 100 Hz periodic interrupt for both timekeeping (think HP-41 Time Module) and keyboard scan and debounce. Unfortunately that rate was too low for the debounce to work well, and I couldn't really increase the interrupt rate.

The rewrite uses the GPIO falling-edge interrupt to start the keyboard scan, using timer interrupts for a few subsequent scans for debounce. I'm struggling with the GPIO interrupts at the moment.

The timekeeping code will have to be completely rewritten, so that it will only schedule timer interrupts as needed.

If I get ambitious, I'll temperature-compensate the timekeeping. That should be more effective than the Time Module's "accuracy factor".

As a result of these changes, the current dissipation in the off state will be lower.

[*] I would have used a priority queue rather than a list, since a priority queue has O(log n) insertion, vs. O(n) for the linked list, but when n is small the linked list is actually more efficient. In the case of this calculator it appears that n will not exceed six. This includes three for the Time Module functionality, which is independent of the number of Time Module alarms that the user sets.


10ms frequency for keyboard scan is adequate. Have a look at my WP 34S code (main.c)!


It's possible that my problem with keyboard scan in the old DIY4 code was not due to the 10 ms periodic interrupt interval being too slow, though that was the appearance it gave. However, by doing away with the periodic interrupt, the power consumption is reduced, and other problems are solved, and the keyboard debounce works better. At this point I don't think I'll bother trying to do further analysis of exactly what the keyboard problem with the periodic interrupt was.

In the new code, timer interrupts are scheduled only as needed, rather than at a constant rate. When the keyboard is idle, it is left in a state where all columns are driven low, and all rows are inputs with pullups, and interrupt on falling edge. When a row-line interrupt occurs, a scan is initiated. If at least one key closure is detected, a timer is scheduled to generate an interrupt and repeat the scan after a delay. The timer will be rescheduled on each interrupt until the debounce logic has determined that all keys are open.

Edited: 7 Apr 2012, 1:32 p.m.


This is following the scheme that Cyrille has adopted for the 20b and 30b (and most probably for all Atmel based designed.) I'm in favour of a continuous timebase for all the timing and house keeping.


Why would you consider that better than scheduling timer interrupts on an as-needed basis? Even the Linux kernel has generally moved to this "tickless" design. It reduces power consumption in the idle and "off" states.


I shut down the processor after half a second of idle time but the ticks remaining are useful for tasks like determining the battery voltage. While a program is running the ticks are counted and presented to the application as a readable TICKS value.


The DIY4X shuts down the processor whenever it has nothing to do, without any delay. After ten minutes it will turn off, which is the same as the idle state except that the display is turned off and only the ON key will turn the calculator back on.

The DIY4X allows a user program to read the current time to a granularity of 1/100 of a second, with a small amount of jitter due to 100 not evenly dividing 32768. It does that without needing a fixed "tick". If there was a good reason to need it, it could provide the time to 1/32768 of a second.

I don't see any use for determining the battery voltage when the calculator is turned off. When it is turned on, it will be sampled at various times, but doesn't need to be sampled at a precise interval, nor very frequently. Most likely I'll sample the battery voltage when the calculator is first turned on, and at roughly one minute intervals until it is turned off.

I find that the DIY4 power dissipation in idle is reduced by more than 50% by doing away with the 100Hz tick.

[Actually at the moment the DIY4 prototypes are using a 60 kHz oscillator rather than 32.768 kHz, and thus can provide "exact" 100 Hz time, but part of the reason for doing away with ticks is to eliminate the need for a 60 kHz crystal and allow use of the more common 32.768 kHz.]

Edited: 7 Apr 2012, 7:23 p.m.


The way the Atmel chip samples the voltage (a single bit brown out detector with programmable threshold) asks for regular checks with a minimum interval in between.

Power usage in idle mode with the interrupts kicking in needs to be measured to higher accuracy than I can provide here. Any takers for the job? To my knowledge, the necessary pull-ups and the LCD account for more than 50% of the power consumption in idle mode. This explains my figures of roughly .25 mA in idle mode (with interrupts running) versus 0.15 mA in deep sleep mode.

The Atmel RTC chip has a resolution of one second, not less.


I instrumented my new tickless timer code and keyboard debounce code, and found that in the worst case it takes only 4.5% of the available time, vs. worst case of over 90% with the old code. The keyboard debounce works fine at 10ms timing (as Marcus stated earlier in this thread). Based on this experience I think I know how I could make the old (tickful) code work better but take less time, but I think I'm better off sticking with the new tickless code.

Apparently the keyboard problem I had with the old code wasn't in the keyboard debounce, but rather that keystroke events were being put in the queue, but not always getting processed. This could be due to that worst-case processor load mentioned above, though I haven't yet verified that.

Nothing I've written about the changes I've been making to the DIY4X code should be construed as suggesting that I am recommending the algorithms for use in any calculator other than the DIY4X. I'm dealing specifically with optimization for the constraints of the DIY4X hardware, which are significantly different than those of HP's Atmel-based hardware.


On that mote, there was program for the Mac a couple of decades ago called 'Calculator Construction Set.' With it, you could build a stand-alone app of your own specialised calculator. And yes, it even has in its toolbar the keys & switches for making an RPN machine. Whenever I made my calcs, the first step was to develop it under an RPN framework.

Edited: 5 Apr 2012, 3:32 p.m.


On that mote, there was program for the Mac a couple of decades ago called 'Calculator Construction Set.' With it, you could build a stand-alone app of your own specialised calculator.

I have a copy of this I don't use. It runs under Basilisk II I believe.

It implements a 41 series machine with some extra features and allows buttons to be linked to programs or functions and displays (yes you can have several) linked to registers.

- Pauli


I have a Samsung Galaxy S2 and I use this *GREAT* program on it. --> Droid 48


And with the Galaxy S II's 4.5" screen (at least on my model), the buttons are actually big enough to use Droid48, unlike my previous phone!



You should try my Galaxy Note then... ;)



And with the Galaxy S II's 4.5" screen...

The 4.5-inch diagonal screens make all the difference in the world for device usability. The improvement over 3.5-inch displays is astonishing, and even the step up from 4.3-inch displays is noticeable. I use my Samsung Infuse 4G as a mini-tablet, viewing and using web sites in their normal (non-mobile) format.

I don't understand how the expensive iPhone's micro-sized 3.5-inch screen could be acceptable except to those who worship at the Apple Altar of Hype. (Some P.T. Barnum quotations come to mind.)

I've found some problems with clock/calendar functions with Droid 48 on my Infuse. I actually use Free42 for real work. That's beautiful on the 4.5-inch screen, and about 450 times faster than the real HP 42S. I like it so much that I seldom bring a real HP 42S with me anywhere.

Edited: 6 Apr 2012, 1:30 p.m. after one or more responses were posted


Ah it wouldn't be complete with you or the other haters hijacking threads to spread more Apple Derangement Syndrome. I'm surprised you didn't call them "Nazis" like you did in a previous thread.

And people who hold up 4.5" screens to their ears to take calls look like supreme dorks. It's why that screen size is not selling as well.


Ah it wouldn't be complete with you or the other haters hijacking threads to spread more Apple Derangement Syndrome. I'm surprised you didn't call them "Nazis" like you did in a previous thread.

Don't get your panties all in a wad, Steve! :-) You really should resist just making things up when you're excited...But I can understand how some react when they think their religion is being criticized.

BTW, I've never called anyone a "Nazi". I take what they did far too seriously to trivialize it in the manner of, say, someone who uses "haters" as a speech prop when unable to argue intelligently. :-)

And people who hold up 4.5" screens to their ears to take calls look like supreme dorks. It's why that screen size is not selling as well.

Oh yeah, Steve...you "3.5-incher" guys really blend! Soooo cool! :-)

But I've got to admit, Steve, you're absolutely correct in every particular there! Plus, all the industry will doubtless be shaken by your dictate that 4.5-inch smartphones are NOT selling well, due precisely to your "supreme dork" factor. Two for two Steve...great! BTW, Steve, what color is the sky in your universe?

By the way...ever hear of a bluetooth headset? No intelligent person that I know uses any cell phone at head level. Why? Ever hear of EM radiation exposure? Or how that makes it impossible to use the web features simultaneously? Or how great it is to have both hands free during a call? Bluetooth, Steve! Try it. And since I feel that we've now "bonded", please think of me whenever you do! :-)


If you'd ever been burned big time by iTunes, you'd understand...

We have had free42 on a first generation Touch and it really is too small.

A slightly bigger screen would probably make considerably better.

Ever tried to ride a bike with the seat 2"too low for more than a few yards? Ergonomics is often about small changes making big improvements.

Edited: 6 Apr 2012, 2:35 p.m.


For me, my 41cx. I worked with a man around 1990 who would come to work with several calculators in his attache case, all HPs IIRC. I guess it just felt good to have them close to him. He had one of those nice little stands to keep a calculator on the desk at a slant. Every so often throughout the day, for no reason or pattern that I could identify, he would put the one he had on the desk back in the attache case and get another one out.


for no reason or pattern that I could identify, he would put the one he had on the desk back in the attache case and get another one out.

perhaps it was because the batteries had gone flat?


No, they were all good, and he might have the same calculator out again later in the day. It was kind of comical watching it.


Honeywell GNS-XL flight management system. Really all I need at work.


HP-41CL w/NoV-64 & Time Module


Secondary calcs:

HP-67 on my office desk
HP-27 in my briefcase


+1 41CL+NoV-64+Time Module


The next version of ND1 with CAS.

[EDIT: Removed funny sentence designed to elicit impulsive response from HP about state of RPL in future calc--it failed :o]

Edited: 6 Apr 2012, 6:16 a.m.


If you are at all like me, you will find yourself going through an ad-hoc rotation. I've had many different machines as a daily use machine, for anywhere from a week or so, to many months at a time.

I have used that idea, the "go-to" machine, as a way to get to know a machine's design.

I've done this with most of my collection, with the exception of the pure business ones and the 45, which the former is useless for science and the latter not practical (battery chargers etc PITA).

I got to know the 20s well by doing this. Same with the 27s and the 48GX. I even gave the 33s and the 35s fairly long exposures back when they were first released. In both cases, I went back to the 32sii and said, "wow, so much better" (except for memory).

The 27s became my favorite until I lost my "beater" copy on a flight last summer. Dammit!

Now I have been trying to make the 30b the daily, but haven't taken the time to RTFM41 so I keep grabbing the 15c or 20s in the drawer for sohcahtoa:-)

Edited: 9 Apr 2012, 10:52 p.m. after one or more responses were posted


SOHCAHTOA! Geesh! That brings back lots of memories!

Yes, that's my other habit, too. I'll pick up an orphan, my 15C, my 32SII or something I've not used in a while and immerse myself to get into its operating characteristics. Perhaps write an algorithm/program or a few. Then, a few weeks, a month later, I'll pick up another lonely soul and start the process all over again.

Although, for me, the 45's not such a problem child. Yes, it has its limitations: one-var stats, rechargeable batteries. But, the functional and computational power I can harness from it, especially with the application pack, make up for the shortfall.

Edited: 5 Apr 2012, 4:52 p.m.


not sure what an "application pac" adds to a non-programmable?


Well, HP came out with several of these Application Books for the 35 and 45. If you've got the MoHPC DVD, these 35, 45, 55 etc. applications books are on DVD I. Considering that they were step-by-step solutions, to use these with your preprogrammed HP-35, 45, 21, 31E and 32E, those cazlculators could be quite the resourceful little brain.

Edited: 5 Apr 2012, 10:57 p.m.


Same here. Unless there is a specific need, I reach into the drawer and just grab one. The idea is to make sure (or get) familiar with all of them. It hasn't worked so well.... :(


At work, it's my 35s, unless I'm doing a detailed calculation that I have programmed on my 50g in nice RPL code with pop-up boxes. --- At home, however, I agree with Bill. I'm in "hobby" mode at home, and routinely change which calculator I'm using from my little collection. Definitely enjoy the RPNs best, but sometimes will grab my TI-86 when I'm in the mood. So at home it's a round-robin of 45, 25, 28S, 41C, 32SII, 35S, 15 LE, 50g, and occasionally the 39g.


I have an old (very old and a little battered) 12C sitting on my desk for basic arithmetic.

Otherwise my calculator of choice is either a 41 (different varieties including CL) or (believe it or not) a 39gs for which I have written several programs I use regularly. I know, I know, that isn't an RPN machine. But I *have* written a 4 position stack RPN emulator for it so I don't go into withdrawal.

Other calculators I use in descending order of regularity:
Various HP48/50 models
HP-17bii/bii+ Silver
HP-15C/15C LE

I play around with the WP34S but I don't tend to grab it when I am doing real work. The funny thing is that I didn't even realize that was the case until just now. I'll have to correct that as I am very happy with the WP34 and really do enjoy using it. I'll have to get around to flashing the latest firmware sometime soon.




If I'm at my computer then it's usually EMU48 (running as a 50g) or the "dc" program.

If I need a physical calculator, it's usually the one on the top of the, uh, stack, next to my desk. Sometimes I need a specific calculator (scientific, graphical, financial, etc) and thus the stack periodically gets rearranged.


Mostly the 48SX I keep on my desk (with a 32KB RAM card).

I usually pull out the 200LX if I need to do some financial work, which isn't often, seeing as I'm a DBA and not an accountant.


41CL, unless I need to do something in hex. Then it's the 16C.


41CL, unless I need to do something in hex. Then it's the 16C.
Does the Advantage module not give enough digits? I use it for hex and binary and boolean operations.

Edited: 5 Apr 2012, 5:34 p.m.


The 41C_ and Advantage module beats the 16C on speed.

Otherwise, it is no match with the 16C, it is not even close.


The same for me


After buying a lot of old units since my calculator crisis began, I have up in my desk rigt now a 28s, 32s, 32sii, 42s, 48s and a 27s. When I´m doing calculations *orderly*, I really like the 28s, which I think it is greatly underrated (although I find anoying it doesn´t use a comma to separate numbers!). When I´m on limited time, I have found that both the 32s and the 42s work great. But when in a rush, no doubt the 42s and the 15cLE are better for me; the first one because of the small size and double line display, the later one because of the form factor (I´m very used to it). Recently I have been using intensively the 27s too, trying to understand Bill Platt´s comments about algebraics, but I haven´t felt that comfortable so I guess am so used to RPN. I think that when my calculators lust is settled, I´d stick to the 42s and 15cLE for my everyday use.


Mine is a very beat up 32S that's older than me by a few months. It's small, the batteries last forever, and it has almost all of the functionality that I need on a regular basis.


Lately, it's been my 10C - in my job I don't really need much more than a basic four function machine and the Voyager fits nicely in my jacket pocket, has good battery life and the 10C has the advantage of a less cluttered keyboard with CLx and % being unshifted so only one keystroke.

There is an attractiveness about a simple layout which also makes the 21 appealing to me although having said that I also like the 3 shift keys of the 34C - contrary human nature I guess.

Recently I've also been taking my 48S to work with a view to getting to grips with it and RPL, slowly working through the manual on the train commute each day.




Great question! My most frequenly used are: (1) Free42 assigned to the calculator key on my Dell keyboard on my Lenovo laptop: Instantly available when at my desk, (2) WP34S on an HHC2008 HP20b (thank you, team!!), (3) HP 50g when I want the graphics, etc. (thank you, Joe!!), (4) and so on (Thank you, CdB and TW!!). They all get used well in all sorts of avionics / electronics / engine systems / aerodynamics / etc. in the design and support of unmanned aircraft systems, personal finance and so on.

What terrific tools - and community, too...


You're welcome. I'm glad you enjoy my question.


Computer: Thomas Okken's fantastic Free42 (also on my smartphone), otherwise (when I have the time) one of Eric's nonpareil gems or my 28s on Christoph's wonderful Emu42.

Calculator: 1984-2011: my trusty 11C, but since this year the terrific WP 34S sees most of the work.

Edited: 5 Apr 2012, 6:58 p.m.


Although I'm a scientist rather than finance person, my everyday machine at my desk (the one I use most) is a 17bII+ (gold) -- the main reason being the ease of plugging in simple equations I often use rather than doing it all on Excel. When I work in a lab it's the WP34s or HP48G. At home I just use a 33s or 35s interchangeably. Not particularly wed to one or the other. When equipped only with a smartphone it's Free42s all the way. My 50g I often pull out when I really need to track history. 15cLE stays in its box...collector's item. And the underrated Casio 9860g slim with Reckon installed is handy to use when you want a big display!


Physicist here...and amateur woodworker and home mechanic. On the run, 11C sim on the Palm and 15C in the pocket when appropriate. I have a Palm 48 sim, too, but it isn't as convenient as the 11C sim, despite the power.

In the shop, 35. That sits in an Otter case in my carpenter's bag when not in use.

At work, 50g. The others are carefully stored...can't bring myself to sell them, but I rarely use them. The 48SX was a gift from HP, so that will never go. Call me silly, eh?

I really liked many of the the earlier machines (loved the Spice series), but the Voyager series takes the cake for most useful day-to-day. Still, I gotta admit that all the conversions on the 50g, and the convenient programming (compared to the 15C) make it a heavy hitter for me. Mind you, I think that the 15C is easier to program at a lower level than the 50g, so it wins there, but the 50g can do much more with a bit of extra effort, and I usually want the larger programming space and ROM power.

Just picked up a 15C LE, and that will be my most used, I'm sure. That's why I got it...save a few miles on the 15C.



Physicist here...and amateur woodworker and home mechanic. On the run, 11C sim on the Palm and 15C in the pocket when appropriate. I have a Palm 48 sim, too, but it isn't as convenient as the 11C sim, despite the power.

I've previously noticed some preference for the HP-11C among physicists, but I'm not sure whether the number of samples is enough:



(A former Physics student, not a physicist)


Well, if it helps your statistics adding one, I had got an 11C (after my 25C) until it was stolen on a train ride.

(W. B. - FISICA-NUCLEAR - Por favor, o que es fisica-noturno? Astronomia?)


My guess is it's portuguese for some kind of night school (Abendschule, berufsbegleitend). ;-)

Edited: 6 Apr 2012, 3:39 a.m.


Thanks! That coincides with my guess - but I want to know. :-)


Thanks! That coincides with my guess - but I want to know. :-)

;-) Wasn't your guess "Astronomia"? How do you explain THAT to mean "night school"?!?! ;-)

BTW, I find "Astronomia" to be a very beautiful and poetic alternate translation possibility of "fisica noturno". I think I will use the German equivalent "Nachtphysik" for astronomy from now on! I like it very much!


Hallo Walter,

Alexander's guess (and yours) is right: Física == Physics, noturno == nightly. The university offered some night courses for students who could not attend day courses. My primary goal was Electrical Engineering then, but I'd been advised to take a Physics course as the former was not available as a day course. After three semesters I switched to Computer Science and attended the classes during two years, but eventually I started an engineering course at another local university. That was crazy: I left work at 05:00 PM and classes began at 05:50 PM, but I somehow survived until graduation :-)
Back to calculators, in '82 when classes began I had a
TI-51-III, soon followed by a TI-59, which was later replaced by an HP-15C.

Best regards,



Impressive stamina - obrigado para a sua explicação d:-)

Edited: 6 Apr 2012, 5:38 p.m.


As a college student, I use one of several calculators depending on the circumstances, mostly voyagers.

For most of my EE classes I use an original 15C instead of my LE, as I prefer the feel of the high-density buttons and the softer response of the round snap domes. The complex number support is very useful here, though I wish it were a little more extensive. Complex value integrals would be awesome (straight line integrals from any two points on the complex plane) as would complex gamma. Nested integration and solving would be awesome too, although I don't know if it would be technically feasible (maybe someone with more of a numerical computing background can chime in). Also would be nice to do away with some of the weird quirks like memory shared between registers and program steps. How about community-developed 15C LE firmware in the vein of the WP 34S? Then we could fix the current draw and PSE bug, too.

I actually met a guy in my signals and systems class with a 15C LE, which was really nice too see. He had opened it up and stuck something behind the shift keys (think he said little eraser heads, but I'm not sure) to stop them from wobbling. Whatever he did, it felt good to me. Made the shift keys feel exactly like the rest of the buttons. On the original 15C, all of the keys are loose (not attached to a single matrix) like the shift keys on the LE. Seems to me that it is just the pressure from the snap domes that keeps them from wobbling, and I'm not sure why a similar approach could not have been used on the 15C LE. I may end up trying his technique myself, though the wobbly shift keys are just a minor annoyance.

For statics and dynamics, the 15C LE was my calculator of choice. Seems like I would always wind up with some weird trig equation and the the original 15C is way too slow to solve equations with one or more trig functions. The numerical integration and matrix capabilities (for solving linear systems) were both extremely useful for that class as well.

For logic design, the 16C was the obvious choice. The professor actually recognized it and played with it a little when he saw it on my desk. On the exams, I would make a first pass where I would do only the questions that I could plug straight into the 16C (base conversions, two's complement, bitwise operations). This would usually knock out about half of the questions (this professor was not the most creative exam writer) and save me tons of time. I also had a little program to iterate through the terms of a boolean expression and create a truth table. This could be used in a pinch to solve multiple choice problems on boolean algebra and logic minimization by just checking all the possible solutions for a truth table match (yep, I'm a cheater). My disorganized ass actually got the time wrong for the final exam and I showed up an hour late, freaking out (it was like a bad dream, only real). Still finished before the rest of the class thanks to my 16C and walked out feeling like Matt Damon from Good Will Hunting.

For my engineering economy class as well I my personal finance calculations, the 12C+ is my calculator of choice. Had an original 12C too but it has now become a donor for other voyagers with mushy snap domes.

For math classes, where I need symbolic answers, I always go with the 50G. I'm actually on my third 50G right now. The first one has a couple buttons that have lost their spring (they still work, but have almost no travel or tactile feedback) and the second one was stolen with my backpack.

For quick calculations at home, I have a 41CV sitting on my desk. I'm sure I would use it all the time for school if I had an advantage pac for it. Sometimes professors will ban the use of graphing calculators on exams, but almost everyone is unaware of this little machine's capabilities. Eventually I'll bite the bullet on the 41CL at which point I'm sure my 41 will make it into my school rotation.

Have a couple woodstocks, but rarely use them for serious calculations because of the shifted inverse key.

I have a 15C on my work desk too, though I rarely use it for my web programming job. Its primary job is summing up my hours.

So there's my overly detailed account of my daily calculator use. Hopefully someone finds it interesting. I've enjoyed reading everyone's responses so far.


Are you a 20 year old college student? If so, it is extraordinary thing for you to be a collector of HPs. How did that come about?


(maybe someone with more of a numerical computing background can chime in)

That's not me, but while he/she doesn't you can take notice of these:

  • For nested integrals refer to Long Live The HP-34C !, by Valentín Albillo;
  • For complex gamma refer to a Viktor Toth's program you can find here.


For complex gamma refer to a Viktor Toth's program you can find here.

Viktor´s pages are priceless, I learned a lot from reading them. I don't use that program though, among many other functions the SandMath Module includes a MCODE function implementing Gamma that also supports the negative axis - save poles.

The 41Z module includes an implementation of Complex Gamma completely in MCODE, supporting all the complex plane except the poles.

edited to add: Provides to what all purposes are instantaneous answers on the CL, seeing is believing.


Edited: 6 Apr 2012, 4:25 a.m.


HP 41 CL .

Don't need a graphing calc. Backup is the 42S, backup to the backup is the 15LE and now playing with the dm15cc.

Have yet to get to the 30b but I will! It's just that it doesn't print.

Cheers, Geoff


"It's just that it doesn't print."

So you have fitted the infrared print eye to the 15C-LE too? That's my favorite modification :-)


Oops, you got me.

Actually, if the 30 transmitted then I would make it the backup to the 42s and leave the 15 le at home.

Should read the post before I submit ;-)


I don't know if this was discussed before but.....

I don't think it would be all that hard to modify a 30b/wp34s to send to an HP IR printer. There are 8 general purpose i/o posts on the PCB and although the ARM chip can only source these particular pins with 2ma of current one could easily add a small transistor to get to 20ma or so to drive a IR LED to decent intensity. You would need to drill a small hole in the case to mount it but there's plenty of room inside for that.

The details of the IR signal are provided in the "HP 82240B Infrared Printer Technical Interfacing Guide" and it's pretty straightforward to send character data or graphics. I'm certain that the W-P-M team (or maybe just M alone) could fit all the needed code in under 2K bytes of ROM (is that how much is left?)

Edited: 6 Apr 2012, 9:42 a.m.


I know how to drill a hole ;-) in a calculator case! The rest of that is well above my pay grade.

Now that would be a slick mod to the 30b.

Thanks for the idea Katie.


any more new england holidays planned?



Wow, Geoff, a clickeykey 9825a! I'm curious - do you prefer to use Firefox or Chrome to browse the web on it? Though an equivalent to Lynx may be possible.

(Unrelated side note: Back then, ASCII keyboards were anything but standardized and the 9825 had a number of keys seen on no other computer. One of the phrases used at Desktop Computer Division (in Loveland where they were developed) for an obscure key sequence was "Backpedal-Swastika". Fortunately, it was never implimented...)


Not that I hadn't thought about the idea. I may need someone to give me the right specs for the parts to add to my 30b so that it's just a software exercise. I'm pretty sure I can fit some printing features into the 34S. I may need to drop some other functionality but that's a matter of discussion. I've no idea how much ROM the coding for the low level access would cost but it should be manageable. I fear that we cannot print all the special characters, except as graphics.

Can some kind soul provide the necessary hardware specs?


There's a partial hardware spec in this document. However IR LED's are much more efficient these days and don't need that much current. So the 18ohm collector resistor should be more like 150 ohms -- this will limit the maximum current draw to about 20ma. The transistor could be any general purpose NPN (using this circuit), a 2n3904 or a 2n2222 are good choices but they should have a resistor in series with the base lead going to one of the gpio pins on the ARM in order to limit the max current draw out of the pin to under 2ma (per Atmel's spec).

The optimum wavelength according to the above document is 940nm, they also specify a 50 degree angle (for ease of use). You can do a parametric search for IR emitters on Mouser, Digikey or other sites and find a number of ones that meet these specs or are close enough to them. You'll want a 3mm or 5mm round led for easy mounting in a hole. Here's one that will be easy to find.

I volunteer to mod my calculator and test whatever code you come up with. Even just some function to blink the IR LED for starters so I can estimate range and tweak the hardware components. I've got some test equipment and both a 82240A and 82240B printers to try this out on.


Looks like you want us radiating some IR energy around. I'm happy with the battery life of my WP 34S so far ... and for I/O we support DSST (i.e. direct solid state transmission, a.k.a. copper cable link) to a PC without losses by blowing electromagnetic waves aside. IR to battery powered printers seems a bit outdated IMHO. YMMV


There's a lot to be said for using a hard wired connection and if printing it could be to a machine with quality paper and decent speed, not something the HP82240A/B is known for.

However an IR link need not be that power expensive when used at close range. The 42s, 17b, etc.. draw a peak of 12ma from the 357 silver oxide (or equivalent alkaline) cells which is way below the peak output of the IR emitters used in these machines. That's why the range is just a couple of feet and yet the harm to the 357 cells so great. Modern IR emitters are more efficient and could run at half that current for the same output. Furthermore two parallel 2032 cells can supply a whole lot more current than a single 357 cell without damage.

I don't see much impact to battery life in adding an IR emitter. If the current were limited to 6 ma (range of a few feet) the need for the printing to run slowly (due to the inherently slow printer) and the low average duty cycle of the emitted IR waveform my guess is that even in a "trace mode" you won't notice much loss of battery life.

The other nice thing about the IR printer is that the standard already exists and is well documented. I suspect many WP-34S owners already have an HP82240A/B printer -- if not, they are still available new. And while it's somewhat archaic it's very convenient way to get a quick printout.

Since you don't need run the printer or mod the calculator, the big cost to having IR printing is ROM space. There's a lot of stuff in the WP-34s ROM now that I can't imaging ever using. IR printing might be the same to you and others. Like you said YMMV.

Edited: 7 Apr 2012, 12:10 a.m.


IR printing is THE ONE THING I really longed for on the WP-34s. So, yeah, we're at least two who would welcome this feature! I currently have one WP-34s V2, two WP-34s V3 and three (!) printers: obviously a perfect match!!!


I agree with Alexander.

I compute 'fuel in tank ' and print out the output which is included in the flight documents. My 41CL does a much better job at discovering fuel shortages due to specific gravity changes.

Also print out break sheds for the long flights as well as being able to create a flight plan from scratch in strip form.

The printer is small and fits in my flight bag.

Also print out antiskid failure takeoff and landing difference penalties so, yes, need a printer option.

That is why the 41 then the 42s are my go to calcs.


Edited: 7 Apr 2012, 3:05 a.m.


I knew you were chiming in. :-)

Katie, send me an email so we can discuss this further. The README has our addresses. From the specs it looks like I need some output that is controllable through a timer to ensure the correct burst patterns are created. A first prototype would probably be on an external board for easier access.


The cookies were much appreciated by Janice and I.

You need testing on the printer ir I am willing! I know how to drill and solder. It will make the 30b my goto!



The cookies were much appreciated by Janice and I.

Thanks. We were fearing they weren't as good as they could have been. Mother is aging.

Before you can test printing I will have to write some code I'm afraid...


Oh Nooooo...! All my 41CL work down the drain...!


Wrong o bucko!

I sleep with my CL!

Familiarity means a lot.

Still exploring the roms!

Never will that leave the flight bag!

I shudder to think of it.

Got the point Monte. ;-)

That's why I have a spare.

Cheers, Geoff 'CL' Quicky.


I think the strong points of WP 34S are its replaceability, speed, accuracy and the fact that programs can be very easily stored in flash. The 41CL has greater versatility, expandability, more storage, ...

They should complement each other, not compete. :-)


What Marcus said ;-))



I'm certain that the W-P-M team (or maybe just M alone) could fit all the needed code in under 2K bytes of ROM (is that how much is left?)

Either Marcus or I are capable of this.

We're running about 8kb clear in flash -- a little over in the standard image, a bit less with the stop watch image. All, otherwise unused, flash is allocated to library. Thus, every function we add to the device means less user library.

- Pauli


At work, an HP-32SII. At home, an HP-15C LE (and before I got my 15C LE, I used a 42S). I also have Free42 installed on all my computers and bound to a hotkey.


WP34S, hands down.

I am glad to have the twenty or so collectibles I do, including a few pieces I spent too much for out of impatience or ignorance. But once I got the hardware figured out, I am just nuts about this project. It does everything I wish my other beloved RPN keystroke programmables could.


Well for routine calculations there is the 97 that is always on my desk, plus for my work as a hardware support person I frequently need to do Hex <-> Dec conversions so my 16C (first HP I ever bought) is not far away. As well as these I have a selection of other HP calculators and handhelds near by that I will use sometime as well, and soon I will add a WP34S to the collection.


Work: HP15c, HP15c LE and the HP15c PC emulator

School: HP50g


My 10bii+ goes with me everywhere but am re-acquainting myself with the wonders of my 27s which I really like.


I agree with the 55, I use it often, but I really don't program much any more. I use Excel for anything non trivial.

I keep a 97 on my desk at home and it gets used quite a bit. If I do want to create some programs, it is usually on the 97 or my 67.

I've mostly retired my 42S. I bought it new in 89 and used it quite a bit for 5 or so years. I create a few programs for it from time to time. I do a lot of reliability engineering so I always have a few utility programs for Weibull and Exponential functions, or converting from FIT to MTTF, etc.

If I'm too lazy to reach into my desk drawer, I fire up free42 on my laptop.


Dan, FYI, Weibull and Exponential are both implemented in the WP 34S :-)


"Dan, FYI, Weibull



Bleah, you're bringing back painful memories, Dan. I used to do reliability calculations (MTBFs) on Navy designs back in the late 80's, before there were computer programs to assist. It was circuit layout in one hand, MIL-STD component reliability list in the other hand, and calculator in my third hand :o/ We've come a long way in the computer world since then.


On my desk at my home office, my 41CX (with Advantage, Stat I, Financial I and infra-red modules) occupies the prime position between keyboard and phone. I sometimes grab my 16C for anything that's logic-related.

I don't leave a calculator on my desk at the university because if I'm using it while working, I'll probably want to continue at home, and I don't have two of any model. I used to tote a 48GX back and forth, but most recently it's either been the 15CLE or 43S; however, I'm still not familiar enough with the keyboards of those machines and find them a bit 'noisy', so when I'm planning intensive work, I'll take the 41CX with me. I really ought to find time to clean up the corroded contact strip in my 41CV, get it working again, and leave it at the university.


--- Les



I used to tote a 48GX back and forth, but most recently it's either been the 15CLE or 43S;

Rats, you got a 43S before us! Send me some pictures, pleeease! ;-)


Rats, you got a 43S before us! Send me some pictures, pleeease! ;-)

Har! That's what I get for letting my fingers work faster than my brain!


--- Les



32SII. Whatever I try, I come back to it, and recently I was gifted another one :-).

On financial things, I rotate between 18C and the new 30b/10BII+. I often take the 10BII+ to work due to form factor and ease of use. The 18C will be retired when the batteries are empty again. Hopefully, I manage to leave the case intact one last time.


HP 15C-LE.

41CV on The desk at home all the time. 35S, 15CLE to take on a rotation basis to the office. I have other 9 HPs bought in the 80' that I use occasionally and never leave the house. On holiday in Rome at moment and have the DM-15CC with me.

After going through a lot of HPs (among other brands) my day-to-day number crunching machine is an HP 11C. Simple but with the most needed functions and landscape so it can sit in front of the keyboard on my desk. Only thing I miss on it is complex but I have a number of other machines when I need complex arithmetic.

At work: 35s.

At home office: 41CX.

At hobby workshop: 29C

Edited: 6 Apr 2012, 3:21 p.m.

HP-12c on my desk, if I am not using my Psion 5 (!).

At home office: 41CX.

At hobby workshop: 29C

The same, except that my 29c is kept at home - too much humidity in my workshop.

Edited: 10 Apr 2012, 8:42 a.m.

Normally I don't need any. While working on the 34S firmware I routinely grab my 16C to do some quick conversions or calculations in hex or octal. Keystroke programming is fun on the 34S or 42S but other machines in my collection get some use from time to time.

All in all it's a hobby, not my job.

I can say that I'm used to apply a sort of turn over to my calculators. Actually I change weekly and my rule is to take with me always a pair of calculators, a scientific with a financial, preferly a LCD + a LED :-). The third, which lies always in the bottom of the briefcase is a graphic 50g that actually is de-facto daily used.
This way I can check periodically the state and the healt of my calculators and the situation of their batteries. Somebody can say that it's better to not stress so much these museum relics, but my opinion is that work is for them like gymnastic for people: it helps to be in a good shape (more difficult is to apply this rule to myself).
For a few years I was used to operate only with a 33c and the 25c of my youth, never I've been away from the last one, even when the last originally battery pack was over and the connector of the charger (I was for that lucky) definitively broken, very far a that time in being capable to feed it with rechargeable single units. Actually I found the 33c display more confortable than the 25c one, for this reason my first love seats on the reserve bench, longer than the others, as well as to run my simple programs I like to operate with the 97 in place of a 67

Edited: 7 Apr 2012, 5:51 a.m.

Usually I have a 32 SII or 32 S near and it's what I use.
Sometimes my wife's 41 CV (what a keyboard!)

Hi all.

As I've recently acquired my new toys, I've developed a particular routine. Since my 55 has pretty much everything I need for RPN calculations, I've been finding myself grabbing that one for my rudimentary number fiddling. As I usually leave the program development and robust calculations to my think-tank--my 15C, 32SII, 42S, 67, 41CV and so forth, my 55's becoming my day-to-day low impact number fiddler.

So, what's your day-to-day calculator?

I have three: HP 50g, HP 15c, TI nSpire CX CAS

Possibly Related Threads…
Thread Author Replies Views Last Post
  12C App kostenlos bei Amazon.de / Android Frank Boehm (Germany) 16 4,077 11-20-2012, 02:24 PM
Last Post: Luiz C. Vieira (Brazil)
  [hp-48] Jean Michel Ferrard "La Maitrise de la HP48 - Tome 2" programs? jerome ibanes 0 855 10-07-2012, 01:33 AM
Last Post: jerome ibanes
  PocketGuide in Portuguese / Guia de Bolso *inside* the HP 50g Software49g 4 1,947 07-18-2012, 02:03 PM
Last Post: Gerson W. Barbosa
  De-allocating memory locations on HP-35s Paul Kleinkramer 7 2,117 08-24-2009, 10:00 AM
Last Post: Paul Kleinkramer
  OT: Business Calculator from Dynatech.de Marcus von Cube, Germany 4 1,561 01-18-2008, 03:28 AM
Last Post: Marcus von Cube, Germany
  33s version at DynaTech.de? Ivan Nejgebauer 2 1,106 05-30-2006, 10:57 AM
Last Post: Marcus von Cube, Germany
  manual de una hp 20s franklin 3 1,201 03-13-2005, 04:55 PM
Last Post: Manuel
  ebay.de price history updated and at new adress Holger Weihe 8 2,080 03-21-2003, 06:33 PM
Last Post: Holger Weihe
  Updated: Calculator sales prices on ebay.de Holger Weihe 2 1,058 12-04-2002, 03:10 AM
Last Post: Holger Weihe
  solicitud de manual Gaspar Ramírez Rodríguez 3 1,101 06-06-2002, 10:04 AM
Last Post: Andrés C. Rodríguez (Argentina)

Forum Jump: