WP-34s: Missed key strokes?


Hi all (*really* long time, no post!):

I just received a WP-34s that I purchased from hpcalc.org. From the start, I have noticed problems with it not registering some of my keystrokes. It does not seem to be limited to one or two *keys*, but rather, it *looks* like the keypad-reading loop in the FW is missing my keystrokes. But I didn't see anyone else complaining about this issue, which would lead me to believe it is *not* a FW issue.

I sure hope that I can get this resolved, because the WP-34s is the *incredible*! It would hands-down be my every-day, go-to calculator, if not for this key-press problem; it just isn't practical to have to visually verify that every keystroke registers.

Any ideas, anyone? Did I just get a lemon underlying HP-30b? Or is this a known FW issue?

Much thanks,


Sorry; I forgot to mention the FW level: 2769.




There have been similar reports and there has been some discussion of this issue. I believe Marcus has looked into keypress handling, but don't know if it was ever fully resolved if this is a hardware or firmware issue. Perhaps Marcus will comment.


I'm the one who wrote the keyboard scan. It should be reliable and I don't have any problems with it. There are complaints from some people which I cannot verify here. I can recommend two things:

- Try your device with the original 30b firmware: Do you have similar problems?

- Try a different device with the 34S firmware: Do you have the same trouble?

A possible reason for keyboard problems is a misplaced overlay obstructing the path of the keys. The 30b is especially picky because the keys rotate and need some headroom directly above the key. If the sheet is glued a little too far 'south' the keys cannot move freely. A sharp blade can help here.

If you are a very fast typer it may help to reactive a special speed-up version of the firmware for you which increases the processor clock when keystrokes start filling the buffer. I hope you have the cable so you can re-flash your device.



Thank you for the detailed response.

Unfortunately, I don't have a cable. I just e-mailed Gene. I hope that he still has some available. If not, are there schematics such that I could make one?

I have access to both another WP-34s (due to my greedy/excited response resulting in the purchase of two), and I also bought a spare 30b from Amazon, so I will definitely perform some experiments.

I don't believe it is a problem of keystrokes filling the buffer, because it can happen on the first or second key-press. It seems to me that it is either flaky hardware, or a FW architecture that can miss a quick keystroke. I'm getting the impression that the FW is not at fault---otherwise many people would be complaining about what I'm seeing.

I know that you have probably heard this many times before, but I want you to hear it again: To you, Pauli, Walter, Eric, and all the others who have invested serious time into making the WP-34s a reality, I owe a *HUGE* debt of gratitude! I haven't followed the MoHPC forum for 10 years---because of the sad decline in HP calculators---but I am now greatly excited about the WP-34s and the other custom-HW / custom-FW offerings! I've worked with enough embedded-FW people to realize the effort involved. I'm heading over to the donation page on Sourceforge right now. You guys have really made a mark!


You missed much of the fun watching the (positive) development of the HP calculator division in the last few years. Without open minded people at HP, namely Cyrille & Tim, giving away enough information abut the 20b/30b line of calculators, the WP 34S would have remained an academic exercise of W & P.

I appreciate your warm words. I'm still hoping the keyboard issues can be sorted out. Are you a 'quick typer' or do you experience the problems even on the first keystroke? I'm asking because I want to make sure the firmware is behaving properly. The debounce algorithm is aimed at debouncing the 'up' state of a key. The reasoning behind it is that the rotate & click mechanism provides a tactile feedback which demands immediate reaction if the key closes the first time. To avoid bouncing, the time a key needs to be up is increased (to cycles of 10ms).

Edited: 16 Apr 2012, 4:54 p.m.


Without open minded people at HP, namely Cyrille & Tim, giving away enough information abut the 20b/30b line of calculators, the WP 34S would have remained an academic exercise of W & P.

We wouldn't have started if the development kit wasn't available.

- Pauli



Everyone involved has done a terrific job; there should be many proud engineers at HP and Agilent!

Thanks for all your hard work,


Pauli, forgot your early designs of a scientific calculator? The history dates back before the advent of the 20b SDK.


Yes, the scientific 4-banger. I'd love to see it in production :-) However I knew it wasn't going anywhere at the time.

Once the 20b dev kit came out, I figured things might go somewhere so I contacted Walter. The rest is history.

- Pauli


And there were some other nice designs I'd also still love to see in production. Well, we will be working on the successors of them once.



The missed keystroke can happen on the first keystroke. I will test-out a 30b and another 34s, and let you know what I find.

Thanks for all your help,


I fear you have a less then perfect hardware. :-(

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