EEVblog #1159 - World's Most Precise Pocket Calculator - Page 1
Forum section: electronics / general

author: EEVblog
author_rank: Unknown
timestamp: December 17, 2018, 12:58:33 pm
content: One item mailbag!A look at the Swissmicro DM42, the world's most precise pocket calculator.A clone and improvement of the famous HP42S, with open source firmware based on the Free42 platform.https://www.swissmicros.com/dm42.phphttp://thomasokken.com/free42/

author: dr.diesel
author_rank: Super Contributor
timestamp: December 17, 2018, 01:39:50 pm
content: That is quite nice! Is the display cover glass or plastic?

author: iMo
author_rank: Super Contributor
timestamp: December 17, 2018, 05:27:58 pm
content: I think the "most precise pocket calculator" is the WP-34S.https://sourceforge.net/projects/wp34s/It uses DecNumber library with up to 50 decimal places precision.

author: bsudbrink
author_rank: Frequent Contributor
timestamp: December 17, 2018, 09:19:13 pm
content: Just so you know, YouTube has this video marked as "unlisted". I'm not sure what this means, but I don't see it on my YouTube account subscription page.

author: darik
author_rank: Regular Contributor
timestamp: December 17, 2018, 11:53:41 pm
content: To show the full precision, use shift-decimal (SHOW).

author: Dubbie
author_rank: Unknown
timestamp: December 18, 2018, 12:56:26 am
content: I have this calculator, the only issue I have with it is that the button feel is not as nice as it could be. It is my daily driver at work though.

author: EEVblog
author_rank: Unknown
timestamp: December 18, 2018, 02:13:37 am
content: Quote from: darik on December 17, 2018, 11:53:41 pmAh, that works, but unfortunately does not show up long enough to read it!UPDATE: You have to continue to hold down the button to keep it showing

author: EEVblog
author_rank: Unknown
timestamp: December 18, 2018, 02:17:54 am
content: Actual Calculator Forensics result:

author: iMo
author_rank: Super Contributor
timestamp: December 18, 2018, 03:35:20 am
content: It seems Dave's buttons diedA big pain all these recent attempts to mimic the original HP-clicky buttons. The WP-34s (HP-30b hw) I own still clicks, but mostly because I stopped using it in order to save the buttonsThe thin plastic pins (about 2.5mm long 1mm dia) pushing onto the metal dome usually bend/broke when pushing a little harder.The DM-42 does not use such long pins, it may last a little bit longer. Not sure you get such HP-feel with it, however.And my HP-25 and HP-48GX is still clicky..

author: BrianHG
author_rank: Super Contributor
timestamp: December 18, 2018, 03:52:42 am
content: Holly cow Dave! Your enthusiasm shines through to the moon.

author: inOr
author_rank: Newbie
timestamp: December 18, 2018, 05:41:53 am
content: Once I tried to write a DEC Fortran program to solve a quadratic the high school way, the exact formula you know -b+/- sqrt(b^2 ...., I got a ridiculous answer, so I tried a numeric routine from the DEC collection and wow was that wrong! So I programmed my own numeric routine and that worked. Meanwhile, I used my HP xx scientific calculator. I can't remember the precision, but the answer was bang-on. They do have their uses...

author: johnlsenchak
author_rank: Frequent Contributor
timestamp: December 18, 2018, 05:49:01 am
content: Years ago, I had a real nice programmable HP scientific calculator where I wrote a programs to calculate A/C circuits when it came to inductors and capacitors .

author: Fungus
author_rank: Super Contributor
timestamp: December 18, 2018, 11:55:17 am
content: Quote from: darik on December 17, 2018, 11:53:41 pmI was shouting that at the screen while the video was running.Quote from: EEVblog on December 18, 2018, 02:13:37 amHow many does it show? 12 digits?

author: NivagSwerdna
author_rank: Super Contributor
timestamp: December 18, 2018, 01:38:24 pm
content: Nice. I have a poor man's version WP 34S . I know 42S is super popular with the fanboys but IMHO it's a bit hard to live with unless you use it every day since the functions are hidden away... I think I prefer the ones that just have lots of functions on the buttons...I also have a HP35S which is a nice compromise and not bad for a modern device.

author: Gribo
author_rank: Frequent Contributor
timestamp: December 18, 2018, 04:07:32 pm
content: Does anyone knows who manufactures the display? I have been looking for an E-paper display with fast response time for quite a while.

author: iMo
author_rank: Super Contributor
timestamp: December 18, 2018, 06:28:00 pm
content: LS027B7DH01 from Sharp Microelectronics..

author: pauli
author_rank: Newbie
timestamp: December 18, 2018, 09:33:30 pm
content: It's off by one in the last digitRefer:http://www.hpmuseum.org/forum/archive/index.php?thread-10355.htmlPauli

author: rsjsouza
author_rank: Super Contributor
timestamp: December 18, 2018, 09:44:04 pm
content: Quote from: NivagSwerdna on December 18, 2018, 01:38:24 pmAlthough a bit more cumbersome to do base conversion when compared to my 48GX, the 35S is quite nice. (I leave my 48GX at home as I am afraid it will be stolen).

author: EEVblog
author_rank: Unknown
timestamp: December 18, 2018, 09:44:25 pm
content: Quote from: pauli on December 18, 2018, 09:33:30 pmHey Pauli, long time no see, welcome to the forum!

author: Spirit532
author_rank: Frequent Contributor
timestamp: December 19, 2018, 01:52:00 am
content: I believe the display is a Sharp Memory LCD with the model number LS027B7DH01It's a ridiculously low retention power graphical LCD, but it comes at a hefty price premium.

author: Fungus
author_rank: Super Contributor
timestamp: December 19, 2018, 10:36:19 pm
content: Quote from: 3roomlab on December 19, 2018, 10:18:21 pmSome of us still have good eyesight and a bit of hand-eye coordination.

author: floobydust
author_rank: Super Contributor
timestamp: December 19, 2018, 10:39:18 pm
content: All these app-based calculators still suck compared to old tech.I have a Sharp EL5103-S that rounds results to engineering units (milli, micro, nano, kilo etc.).It's great instead for EE work, instead of converting exponents.The pocket calc speed test I did was always 69! (69 factorial), I wonder how long that takes on this calculator. TI-30 LED was 2 seconds lol.

author: rsjsouza
author_rank: Super Contributor
timestamp: December 20, 2018, 03:27:50 am
content: Quote from: 3roomlab on December 19, 2018, 10:18:21 pmMy old Kindle Fire HD still has a beautifully coded HP-12C in voyager style. Although its size and functionality are quite nice, pressing virtual buttons is not the same at all. YMMV, though.Quote from: floobydust on December 19, 2018, 10:39:18 pmHeh, I did the same. My old Casio fx-39 took about 10 seconds! My dad's TI-59 did not have a built-in factorial function, and the best program I could make at the time took somewhere between 10 and 15 seconds.

author: Fungus
author_rank: Super Contributor
timestamp: December 20, 2018, 07:49:09 am
content: Quote from: rsjsouza on December 20, 2018, 03:27:50 am12C? Ew! That's a calculator for bankers.HP does the 15C (scientific) for Android:https://play.google.com/store/apps/details?id=com.hp.hp15c15&hl=en_US(it turns into an RPN four-banger when you rotate to portrait mode, too)

author: rsjsouza
author_rank: Super Contributor
timestamp: December 20, 2018, 09:39:58 am
content: Quote from: Fungus on December 20, 2018, 07:49:09 amIt wasn't for me...In reality, it is a great calculator for the real-world issues and served me well to go through the pitfalls of house financing back in 2010 and still is sporadically used for the eventual finance/investment.Hey, a dude's gotta do what it is gotta do to offset the fact money does not grow in trees...Quote from: Fungus on December 20, 2018, 07:49:09 amFor scientific I will keep my HP48 simulator instead, though. It does not replace my physical calculator, but it is darn convenient.

author: Fungus
author_rank: Super Contributor
timestamp: December 20, 2018, 10:06:41 am
content: Quote from: rsjsouza on December 20, 2018, 09:39:58 amI like the shape/format of the Voyagers but my favorite in use is the HP20S. Not much to look at, but quite a beast under the covers. Plus: I can do hex<->decimal conversions and inches<->mm with a single (shifted) key.Not RPN though, so HP purists will hate it.

author: Grapsus
author_rank: Regular Contributor
timestamp: December 20, 2018, 02:11:55 pm
content: I'm genuinely curious, do you still have an actual use for a standalone calculator in your everyday life ?I mean, I love calculators, and I always have a TI 86 (my favorite calculator of all times) on my desk. But with modern computers and high level programming languages I tend to always have a window open with interactive Python or Haskell. Those are so expressive and so handy that they tend to complete replace my use of the TI 86. Even when I do amateur electronics, the fact that I can copy paste from datasheets and write to files is a game changer. How about you ?

author: Fungus
author_rank: Super Contributor
timestamp: December 20, 2018, 02:41:40 pm
content: Used my HP20C about ten minutes ago.5 Volts divided by 33 Ohms....(was feeling too lazy to use my slide rule)Would a Python shell have been more convenient for that?

author: rsjsouza
author_rank: Super Contributor
timestamp: December 20, 2018, 03:09:52 pm
content: Grapsus, I usually use my two calculators to do base conversions, arithmetic and, through the power of programming, do some Q arithmetic and floating point conversion. They sit quite conveniently on my desk.At work I am frequently having to debug these types of data directly on a device's memory.

author: Grapsus
author_rank: Regular Contributor
timestamp: December 20, 2018, 03:30:35 pm
content: Quote from: Fungus on December 20, 2018, 02:41:40 pmThat might be scary but I would say yes if I'm at my computer when I need this computation.I would bring the menu with the windows key, type "ipyt", enter, that would open the python shell and I would type "5./33", enter:In : 5./33Out: 0.15151515151515152The whole operation literally took under two seconds.

author: HKJ
author_rank: Super Contributor
timestamp: December 20, 2018, 04:19:15 pm
content: It looks like a very nice calculator, but I do not have any use for it. When out I use my phone and when home I use one on the computer I wrote many years ago (File date says 2012 but it is older), it works fine on newest Windows:It is a bit more than just a calculator.

author: 0xdeadbeef
author_rank: Super Contributor
timestamp: December 20, 2018, 04:39:00 pm
content: Quote from: 3roomlab on December 20, 2018, 10:23:00 amIf "nPr" is supposed to mean "Nth Power of", this result seems to be totally wrong.The correct result should be 0.7079811261048173e+18495.Quote from: 3roomlab on December 20, 2018, 10:23:00 amWhich seems to be also wrong as the result should be 8.0816921258603719e+22668.Quote from: 3roomlab on December 20, 2018, 10:23:00 amOn my Core i7-6700K, theJava CalculatorI wrote in 2004/2005 and updated now and then takes about a second to come up with 0.3678812805793781e+499995.It uses a BigDecimal fractional representation with "endless" rational accuracy, so I would hope the result is correct. At least Wolfram Alpha seems to come up with the same result:https://www.wolframalpha.com/input/?i=99999**99999

author: Fungus
author_rank: Super Contributor
timestamp: December 20, 2018, 04:43:39 pm
content: Quote from: 0xdeadbeef on December 20, 2018, 04:39:00 pmLuckily it isn't, it's a permutation.

author: Howardlong
author_rank: Super Contributor
timestamp: December 20, 2018, 04:46:34 pm
content: Quote from: rsjsouza on December 18, 2018, 09:44:04 pmThe base conversion aspect is my biggest dislike on the 35S.Some other comments...I recently got around to getting a WP-34S, and I'm really liking it despite the fact that some of the common scientific functions aren't primary key operations. My only calculator with a direct Log base 2 function. It also has a satisfyingly complicated looking keyboard, a key requirement for any self respecting nerd.I agree about the apps on phones, or indeed tablets or a PC, I find that the user experience is compromised badly.QuoteYes, several times a day, both for programming and electronics. See my note above about user experience. It has to be sitting on the desk permanently, if it's kept in a drawer it's far less likely to be used.

author: 0xdeadbeef
author_rank: Super Contributor
timestamp: December 20, 2018, 05:00:04 pm
content: Oops. So you mean "n!/(n-k)!"? While I can't see the benefit of using that instead of n! which will give the same number obviously for n==k (as 0!=1).fac(99999)/fac(99999-99999)out = 28.2422940796034787e+456567Needs about a second.

author: Grapsus
author_rank: Regular Contributor
timestamp: December 20, 2018, 05:59:06 pm
content: Quote from: Howardlong on December 20, 2018, 04:46:34 pmCould you elaborate on how a full keyboard and a 20+" color screen compromise the user experience ?Meanwhile in GHCi:Prelude> let n `nPr` r = product [n-r+1..n]Prelude> 26 `nPr` 4358800Prelude> 6000 `nPr` 60002683999765726739596116316647462735512205018...(it actually spits all the digits without rounding and it's instantaneous)

author: Fungus
author_rank: Super Contributor
timestamp: December 20, 2018, 06:21:45 pm
content: Quote from: Grapsus on December 20, 2018, 05:59:06 pmYou had to type in all that " let n `nPr` r = product [n-r+1..n]" rubbish.On my HP 20S it's a single button press.200 nPr 200 = 7.88657867356e+374

author: emece67
author_rank: Frequent Contributor
timestamp: December 20, 2018, 06:59:18 pm
content: .

author: 0xdeadbeef
author_rank: Super Contributor
timestamp: December 20, 2018, 07:02:38 pm
content: Quote from: Fungus on December 20, 2018, 06:21:45 pmLetting aside that this obviously more than one button press, the result is actually wrong in the two least significant digits displayed. Or maybe this was a mistake when copying typing in the number.Which is also something that is very convenient about PC based calculators: you can just copy/paste values.For the record: the correct result is788657867364790503552363213932185062295135977687173263294742533244359449963403342920304284011984623904177212138919638830257642790242637105061926...So the last three digits should be 365 (rounding up) and not 356.

author: 0xdeadbeef
author_rank: Super Contributor
timestamp: December 20, 2018, 07:05:28 pm
content: Quote from: emece67 on December 20, 2018, 06:59:18 pmThere was a dispute this year but all the source code is available now since several months.https://github.com/swissmicros/free42

author: Fungus
author_rank: Super Contributor
timestamp: December 21, 2018, 10:15:08 am
content: Quote from: 0xdeadbeef on December 20, 2018, 07:02:38 pmYep, I copied it wrong, it should be: 7.88657867365e+374

author: Fungus
author_rank: Super Contributor
timestamp: December 21, 2018, 10:22:21 am
content: Quote from: 3roomlab on December 21, 2018, 12:46:26 amThe exact same way they do numbers with "single" precision - they write some code to do it.

author: iMo
author_rank: Super Contributor
timestamp: December 21, 2018, 01:06:08 pm
content: QuoteIt is called arbitrary precision.For example with the "decNumber" math library (used in WP-34s) you may go for up to a billion digits of precision and 9-digit exponents (by changing a single parameter in the source).The library was written by the IBM btw., not the Digital Equipment Corp.

author: Poupsfamily
author_rank: Newbie
timestamp: January 01, 2019, 06:17:17 pm
content: Hi all and happy new year to everyone.Thanks to accept me on this forum.I have a DM42 too, and it's a great calculator, yes, but...Mine have problem with battery consumption. I need to change the battery CR2032 every month (more or less).Is any one has ever measure power consumption of the DM42. I'm using the last firmware but without improvement.Any information on this problem ? Is it normal ?Thanks

author: Thomas
author_rank: Regular Contributor
timestamp: January 02, 2019, 01:54:31 pm
content: My DM42 drain the batteries in a few weeks too.I measured the current drain: 129µA when off, 160µA when on. Way too much when off, should be <10µA.Mailed Swissmicros about the issue and got a reply saying it's probably C5 and C6 leaking.I will replace the caps myself soon.

author: SiliconWizard
author_rank: Super Contributor
timestamp: January 02, 2019, 03:44:29 pm
content: Quote from: Thomas on January 02, 2019, 01:54:31 pmI was also wondering about the screen displaying a still image when the calculator is off.If I'm not mistaken, this is a Sharp memory LCD. I've already worked with smaller ones (B&W and color ones) and those are fantastic. But they still draw some current to keep displaying an image, even if not much. And If I remember well, this larger screen needs a 5V supply; I'm not sure how the power supplies are handled in the DM42 so not sure if it needs a step-up or SEPIC switching reg, which would further add to the power draw in "off" mode. My point is that some of the "off" current may be due to the screen not being off. Can this feature be disabled, and if so, have you tried measuring the current drain when the screen is completely off (again, not even sure this is possible)? Would have to check in the screen's datasheet as well for some figures. Will do later.

author: Thomas
author_rank: Regular Contributor
timestamp: January 02, 2019, 07:38:21 pm
content: Quote from: SiliconWizard on January 02, 2019, 03:44:29 pmI have now replaced C5 and C6. That helped a lot, the current consumption is now ~4.5uA when off.A CR2032 cell is around 230mAh and will last around 6 years at that current.I have not seen any possibility to turn the screen off, but I haven't looked hard either.Anyway, I don't think it's necessary given the "calculator off" current consumption and the battery capacity.

author: SiliconWizard
author_rank: Super Contributor
timestamp: January 02, 2019, 08:05:00 pm
content: Quote from: Thomas on January 02, 2019, 07:38:21 pmThat was quite a leakage! About 125µA... What kind of capacitors were they?Quote from: Thomas on January 02, 2019, 07:38:21 pmYes, that's interesting actually. If I got it right, the screen must be a Sharp LS027B7DH01. From the datasheet, its nominal supply voltage is indeed 5V as I remembered. They state a typical static power draw of 50µW.If the DM42 is powered by a single CR2032 cell (is it? or is this 2 cells?), then it must have a step-up regulator for powering the screen. The typical total static current draw on a single cell would probably be over 50µA (and assuming a very low power step-up reg). So I'm thinking they may have found out that the screen retained its image down to a much lower voltage than 5V, at a much lower power draw than the typical. I don't think I have seen anything about this in the datasheet which is kinda minimal. I would be interested in knowing more about this, as I've used this kind of screens but never thought of the possibility of leaving them on at all times (while on batteries) due to a bit too high static current draw (but I never bothered to fiddle with supply voltage and such).

author: Thomas
author_rank: Regular Contributor
timestamp: January 03, 2019, 08:06:53 am
content: Quote from: SiliconWizard on January 02, 2019, 08:05:00 pmC5 and C6 are ceramic capacitors, 100uF, 1210 size, probably X5R type. They don't leak 125µA DC (I tested after taking them out) but I think they have high dielectric losses.I replaced them with 10uF X7R type, works fine.The calculator is powered from a single CR2032 cell.You are probably correct they are running the screen at a lower voltage when off, just for retaining the image.For more information, check this thread over on HPmuseum.org:http://www.hpmuseum.org/forum/archive/index.php?thread-10143.html

author: Kean
author_rank: Unknown
timestamp: January 03, 2019, 10:43:10 am
content: May not be leakage of the capacitors, but from flux residue - or a combination of the two.

author: EEVblog
author_rank: Unknown
timestamp: January 04, 2019, 01:47:54 am
content: I was hoping this leakage thing could be video worthy, but just measured mine and only got 5uA. I hate when stuff works

author: Kean
author_rank: Unknown
timestamp: January 04, 2019, 05:38:55 am
content: Quote from: EEVblog on January 04, 2019, 01:47:54 amThose of us who create and ship products think a little differently!Actually, you do that too...

author: Thomas
author_rank: Regular Contributor
timestamp: January 04, 2019, 07:04:57 pm
content: Quote from: EEVblog on January 04, 2019, 01:47:54 amToo bad your unit is OKI think that could have been a great video, as I think quite a few people are experiencing this issue.Swissmicros asked if I felt competent to replace the capacitors myself, which I said yes to. They said it would not void the warranty, and they would be happy to send the caps to me. No need for that. Easy for me, easy for them.Refreshing to see this kind of support in this day and age. Especially for this kind of product.

author: SiliconWizard
author_rank: Super Contributor
timestamp: January 05, 2019, 01:41:44 am
content: Quote from: Thomas on January 04, 2019, 07:04:57 pmYes, it's very impressive. The fact that even merely opening the case would not void the warranty is a big plus, not to mention replacing components. Of course they saved some of their own time, so that was a win-win. Kudos to them.

author: EEVblog
author_rank: Unknown
timestamp: January 05, 2019, 05:56:38 am
content: Quote from: Thomas on January 04, 2019, 07:04:57 pmYep, very dissapointed!Quote

author: Leo Corradini
author_rank: Newbie
timestamp: January 05, 2019, 08:21:37 pm
content: I just love being able to print on my hp 82240B printer with the hp42s!

author: jklasdf
author_rank: Regular Contributor
timestamp: April 26, 2019, 09:15:44 am
content: emece67 is right about not all of the firmware being open source. The code is arranged so that there's still a completely closed-source OS "shell" that just runs one application, a port of Thomas Okken's Free42 (which itself is properly open source and licensed under the GPL). Seehttps://www.hpmuseum.org/forum/archive/index.php?thread-10870.htmlfor further discussion.Several months ago, swissmicros did reorganize things and make available some code on github as 0xdeadbeef states, but the OS "shell" itself is still distributed only as a binary. For example, I wanted to look into the keyboard debouncing algorithm used, and change it to use something similar to what's described here:https://summivox.wordpress.com/2016/06/03/keyboard-matrix-scanning-and-debouncing/. But the source code isn't available. All that swissmicros did was provide an "SDK" so that you can build a new application on top of their closed OS "shell".Nonetheless, several months ago, when swissmicros reorganized things as a separate OS "shell" running Thomas Okken's Free42 application, a lot of people congratulated swissmicros for finally making things "open source", which confuses things. But they really didn't do much more than is legally required (and which they arguably should have had properly separated in the first place). There is still no way to build/modify the code for the lower-level parts of the calculator. And I do think their keyboard debounce algorithm is probably suboptimal (a lot of recent calculators that use a flash microcontroller instead of a custom ASIC or masked rom do seem to get this wrong for some reason...key debouncing just doesn't seem to be get enough attention for firmware development). The DM42 does also have keyboard issues related to the hardware itself (dirty contacts), but there's no way to verify if the debouncing algorithm makes things worse.For comparison, finding the code for the WP-34s is incredibly easy, and I would consider it a truly open-source calculator (at least the firmware). The algorithm used is a lot simpler than what is described athttps://summivox.wordpress.com/2016/06/03/keyboard-matrix-scanning-and-debouncing/. The code for debouncing on the WP-34s can be seen at:https://sourceforge.net/p/wp34s/code/3903/tree/trunk/main.c#l312Code:#ifdef DEBOUNCE_ON_LOW/** A key is newly pressed, if* a) it wasn't pressed the last two times checked* b) it is pressed now*/keys.ll &= ( ~last_keys & ~KbDebounce );#else/** A key is newly pressed, if* a) it wasn't pressed last time we checked* b) it has the same value as the debounce value*/keys.ll &= ( ~last_keys & KbDebounce );#endifCurrently DEBOUNCE_ON_LOW is defined, so the code used for debouncing is the top part. The rest of the keyboard handling is a little more complicated, because it also needs to handle keys held down. (If a function key is held down, that key's function is displayed. If it's held down for even longer, eventually "null" is displayed and the key doesn't do anything when released. This is useful for when you forget what key's assigned to what with custom keyboard assignments in user mode). For me, the biggest usability issue with the WP-34s is the keyboard. The keys themselves give a nice definite click, but I can't always be 100% sure that there aren't repeated or missing keystrokes, although it's maybe fine 99.99% of the time. I think the debouncing is still slightly better than the stock HP 30b firmware (which the calculator is based on). The DM42 is far worse with missing keystrokes.On the WP-34s though, there's also an incredibly annoying delay between when you press the key, and when it actually takes effect. I think the key function/"null" display handling is what causes the delay. It'd be interesting to see the code for the DM42. The code for swissmicro's voyager models is more freely available, although the deboucing isn't great, see dm_lpc111x_sdk/drivers/keyboard/keyboard.c line 252 inhttps://www.swissmicros.com/dm_lpc111x_sdk.tar.gzCode:if (!gpioGetValue(ROW(j)) || !gpioGetValue(ROW(j)) || !gpioGetValue(ROW(j)))keys[press_count++]=KEY_CODE;The key must be polled as being pressed down three times consecutively to register. If the DM42 is using similar code, depending on the polling interval used on the DM42, this might be a problem.

author: 0xdeadbeef
author_rank: Super Contributor
timestamp: April 26, 2019, 09:54:42 am
content: I just wonder: did you bring that up in their forum?It's very hard to judge that without some insight, but I'd imagine a small company like Swissmicros is scared of Chinese copycats and tries to hide some of their IP by keeping it closed source.I guess for a full open source version you need to wait for the 43S. At least I would think they won't rely on any closed source remnants.

author: jklasdf
author_rank: Regular Contributor
timestamp: April 26, 2019, 05:58:54 pm
content: Hi, I haven't brought up the licensing/source code availability in the swissmicros forum (I don't have an account), but unfortunately I do think the OS "shell" being closed source is completely intentional. To be fair, Michael at Swissmicros did put a lot of work into the DM42 and does of course have the right not to release the OS "shell" including the keyboard handling routines. I personally would like to be able to see and modify the source code for the keyboard handling routines, but there's no legal requirement for Swissmicros to do so. Unfortunately a lot of people mistakenly believe that the entire source code for the calculator is open source, but this is not the case.Swissmicros have modified their build so that it is possible to build and run modified versions of Thomas Okken's Free42, but these modified .pgm files must run on the OS "shell" for which the source code is unavailable. Their official license statement is here (note that there is no intention of releasing the "system" protion of the code):https://www.swissmicros.com/License_Statement.php

author: 0xdeadbeef
author_rank: Super Contributor
timestamp: April 26, 2019, 06:35:56 pm
content: I actually meant if you brought up the potential debouncing issue in the Swissmicros forum. I guess there is certain chance you will be listened to.Besides, Michael Steinmann answered per email the last time I tried, so it's not like there is no way to communicate.

author: jklasdf
author_rank: Regular Contributor
timestamp: April 26, 2019, 07:47:29 pm
content: Thanks I'll look into creating a forum account or emailing if he is responsive sometime this weekend. I assumed you meant the licensing part given the rest of your post and your original post trying to correct emece67.

author: Thomas
author_rank: Regular Contributor
timestamp: November 15, 2021, 07:14:39 pm
content: Long time, low activity on this thread.I measured the standby current consumption on my DM42 again today, still ~4.5µA, all good.Then I discovered, by accident, when I press a key (any key) the current draw is ~4.7mA. Pressing more than one key doesn't change it.That can't be good for battery life?Sure, buttons are not pressed for long periods of time. But then again, there are a lot of key presses! That's kinda what you do with a calculatorCan this be a design issue?A normal keyboard matrix with scanning wouldn't cause this kind of current?Edit:Just realized Swissmicros have their own forum, posted there too.

author: EEVblog
author_rank: Unknown
timestamp: November 22, 2021, 04:40:19 am
content: Quote from: Thomas on November 15, 2021, 07:14:39 pmSurely that wouldn't be the keypad matrix, it almost certainly would be the processor waking up and processing at full speed?That being said, for just processing a keypress, there is no need to run the processor full speed.

author: Thomas
author_rank: Regular Contributor
timestamp: November 22, 2021, 01:00:51 pm
content: Yeah, seems excessive to me. Should be easy enough to fix.Might not be deemed important enough to warrant a firmware update.

author: astra4
author_rank: Newbie
timestamp: October 01, 2024, 11:16:35 am
content: Can't find C6 on the PCB of my DM42, there's a C5 near the battery, does the PCB of your DM42 look the same (see the attached photo)?

author: astra4
author_rank: Newbie
timestamp: October 01, 2024, 03:34:48 pm
content: Need to look into how I can measure the standby current consumption of mine...

author: SiliconWizard
author_rank: Super Contributor
timestamp: October 01, 2024, 08:37:39 pm
content: Oh, a STM32L476, I've used it in a couple projects. Now considering switching to the U5 series (lower power yet and significantly higher performance, more RAM, etc). Not evaluated it yet though, but I'm sure Swissmicros would benefit from making that switch too for their newer calculators.

author: Thomas
author_rank: Regular Contributor
timestamp: October 02, 2024, 03:06:02 pm
content: C6 on my calculator is right there in the middle.Do you have a newer hardware revision?