John's Vademecum - public:calculator:info

DM15L Info

anonymous@undisclosed.example.com (Anonymous) — Sat, 04 Apr 2026 10:40:50 +0000

←Calculator Hardware

DM15L Info

Purchase Information

Date : September 2021
From : Swiss Micros (direct)
Price : £95
Serial : 21350
New Battery
- July 27^th 2022
- July 26^th 2024

Firmware

Upgrade firmware on Linux

sudo lpc21isp <firmware_file> /dev/ttyUSB0 115200 12000

bash scripts

just to reduce the typing…. still need to press the hidden reset button to start the flashing and to start the new firmware.

You can have separate scripts for ease of loading different firmware

./lf_flash.sh

#!/bin/bash
#
 
FWARE=LF15C_250408.hex
 
lpc21isp $FWARE /dev/ttyUSB0 115200 1200

./dm32_flash.sh

#!/bin/bash
#
 
FWARE=DM15_M1B_32.hex
 
lpc21isp $FWARE /dev/ttyUSB0 115200 1200

./dm34_flash.sh

#!/bin/bash
#
 
FWARE=DM15_M1B_34.hex
 
lpc21isp $FWARE /dev/ttyUSB0 115200 1200

Upgrade firware on Windows

Serial USB Driver for Windows

cp210x_universal_windows_driver.zip

Windows Firmware Upload Tool

voyage_firmware_tool.zip

Swiss Micros Official

Swiss Micros Firmware files

Date	Serial No.	Firmware	Version	Firmware Files	Comments
24/05/22	21350	DM15_M1B	32	dm15_m1b_32.zip	Extended User Registers
22/11/23	21350	DM15	32	dm15_32.zip	Standard User Registers
21/12/24	21350	DM15_M1B	33	dm15_m1b_33.zip	New 2-line stack and other mods
23/01/26	21350	DM15_M1B	34	dm15_m1b_34.hex	Bug fixes to new version

ROM	Allocatable registers	RAM base addr.	Initial Memory Status
DM15 (Original ROM)	64	0xc0	19 46 0-0
DM15_M80	128	0x80	19 110 0-0
DM15_M1B	229	0x1b	19 211 0-0

LF15C - 3rd Party Firmware

From HP Forum https://www.hpmuseum.org/forum/thread-20046.html

For more details see LF15C - firmware for the DM15

DESK-15 - 3rd Party Firmware

From HP Forum https://www.hpmuseum.org/forum/thread-23488.html
You Tube https://youtu.be/ktrKZzN3wJw
Github for firmware and brief README guide https://github.com/zooxo/desk15

I'll try it out and write up some details…..

Desk15 - firmware for the DM15

RTC Error

RTC is not capable of calibration/correction
RTC appears to continue running even when switching firmware
- LF15C has no ability to display RTC but it the rate appears unaffected by the firmware changes
- Requires that Swiss Micros firmware is loaded in order to check current RTC time

Update January 2026

Using my python Watchcheck

Date Start	Date Check	Delta	Latest Rate Error	Average Rate Error	Comments
23/01/26		-49.0			Delta -49.0. New firmware DM15 V34 loaded. New Period
23/01/26	24/01/26	-47.0	+2.1	+2.1	After 24 hours
23/01/26	26/01/26	-43.4	+1.9	+2.0	After 3 days
23/01/26	27/01/26	-41.9	+1.8	+1.9	After 4 days. LF15C loaded after time check
23/01/26	11/02/26	-11.2	+2.0	+2.0	After 19 days. DM15_M1B_34 reloaded to check time
23/01/26	04/04/26	+88.3	+1.9	+1.9	After 71 days

Swiss Micros Info

Firmware : https://technical.swissmicros.com/voyager/firmware/
Documentation : Online HTML User Manual
Documentation : PDF Manual
Product Page : DM15L

HP-15C Owner's Handbooks

Download from https://literature.hpcalc.org/

HP-15C Owner's Handbook : https://literature.hpcalc.org/community/hp15c-oh-en.pdf
HP-15C Advanced Functions Handbook : https://literature.hpcalc.org/community/hp15c-afh-en.pdf

DM15L Memory Dumps and Program Listings

See DM15L Progs

calculator, dm15l

DM16L Info

anonymous@undisclosed.example.com (Anonymous) — Sun, 01 Feb 2026 08:35:44 +0000

←Calculator Hardware

DM16L Info

Purchase Information

Date : August 2022
From : Swiss Micros (direct)
Price : £
Serial : 04710

Firmware

Date	Serial No.	Firmware	Version	Firmware Files	Firmware Tool
01/09/2022	04710	DM16	32	dm16_32.hex
28/01/26	04710	DM16	34	dm16_34.hex	Linux using lpc21isp

sudo lpc21isp DM16_34.hex /dev/ttyUSB0 115200 1200

RTC Error

Start	Stop	Accumulated Error (s)	Rate Error (s/d)	Comments
18/09/22	15/04/23	+94.6	+0.5	94.6s in 209 days = 0.45 s/d

Using my python Watchcheck

Date Start	Date Check	Delta	Latest Error	Average Error	Comments
28/01/26		+1.9			Time reset during firmware update. New Period

Swiss Micros Info

Firmware : https://technical.swissmicros.com/voyager/firmware/
Documentation : Online HTML User Manual
Documentation : PDF Manual
Product Page : DM16L

HP-16C Owner's Handbook

Download from https://literature.hpcalc.org/

HP-16C Owner's Handbook : https://literature.hpcalc.org/community/hp16c-oh-en.pdf

DM15L Memory Dumps and Program Listings

See DM16L Progs

calculator, dm16l

DM32 Info

anonymous@undisclosed.example.com (Anonymous) — Tue, 14 Apr 2026 13:44:01 +0000

←Calculator Hardware

DM32 Info

The new entry-Level do-it-all machine

Release June 2023 with Beta Firmware - community providing feedback of bugs and errors to help drive firmware development

https://forum.swissmicros.com/viewforum.php?f=33

Photos

Purchase Information

Date : July 2023
From : Swiss Micros
Price : CHF249 + CHF70 DHL Delivery = CHF319 = £296
Serial : 00812

Firmware

Date	DM32 Version	DMCP Version	Firmware Files	Comments
20/07/23	2.03	3.50t25	dmcp5_flash_3.50t25_dm32-2.03.zip	Equation Solver Bug - sometimes shows LOG(0) or DIVIDE BY 0 - also Complex powers bug - Forum says “fixed in next F/W release”
01/08/23	2.04	3.50t29	dmcp5_flash_3.50t29_dm32-2.04.zip	Bugs I'd spotted in 2.03 now resolved
13/09/23	2.05	3.50t31	dmcp5_flash_3.50t31_dm32-2.05.zip	4-line prog editor, 4-line EQN list & more
09/11/23	2.06	3.50t33	dmcp5_flash_3.50t33_dm32-2.06.zip	Various fixes & new features
06/05/24	2.07	3.50t36	dmcp5_flash_3.50t36_dm32-2.07.zip	Various new features including “remote calls” to routines in non-loaded calculator “states”
06/05/24	2.08	3.50t38	dmcp5_flash_3.50t38_dm32-2.08.zip	USB Speed Up and other new features
07/05/24	2.09	3.50t38	dmcp5_flash_3.50t38_dm32-2.09.zip	Right-align stack display option
20/08/24	2.10	3.51	dmcp5_flash_3.51_dm32-2.10.zip	Official Release Version
24/01/26	2.11	3.56	dmcp5_flash_3.56_dm32-2.11.bin	Minor bug-fixes

Changes

Changelog

DM32 v2.11: 2025-12-05

Fixes

  Fixed: crash after using equation solver with Flag-11 (forum)
  Font design: visually improved a selection of glyphs in the SwissKeys font (the "bold" font).

DM32 v2.10: 2024-08-17

Fixes

  Fixed: Difference in error messages (STAT ERROR and INVALID y^x)
  Fixed: SOLVE (i) asks for solve variable

DM32 v2.09: 2024-05-06

Enhancements

  Added RANDSEED to statefile
  Statefile parsing enhancements
  Stack Right-align option (see in doc)

DM32 v2.08: 2024-03-18

Enhancements

  Added CPU frequency switching when powered from USB
  Added remote calls from CALC mode
  Added Extended GTO functionality (see in doc)
  Added support for automatic load of dependent states (see in doc)

Fixes

  Fixed: The '0' style doesn't match register font in SHOW box
  Fixed: F3 (SST) should act only if no other key processing is pending
  Fixed: F3 (SST) long press to NULL behavior
  Fixed: Remote XEQ calls to current context
  Fixed: First remote XEQ call should clear remote call stack
  Fixed: Current state filename should be pre-selected in "Save" dialog

DM32 v2.07: 2023-12-08

Enhancements

  Added remote XEQ functionality (see in manual)
  Added SHOW view of EQN message
  SHOW extended to all program lines in program mode

Fixes

  F2 key (i.e. debug view toggle) deactivated for non-CALC modes and during number entry
  Fixed USB disk id to 0483:5720 so it corresponds to USB MSC by STM
  Fixed: Program SOLVE ending in "NO ROOT FOUND" prevents subsequently keyed XEQ from running (until pressing [R/S])
  Fixed: Number entered as '1E-' ([E][+/-]) should be interpreted as '1'
  Fixed: Message triangle cut-off after File->Load Clean State
  Fixed: Left/right scrolling of long EQN message (i.e. EQN in PRGM mode with flag10 set) doesn't work

DM32 v2.06: 2023-11-01

  Added "Debug View" (see in manual)
  Added Step-out and Step-over (see in manual)
  SHOW box style changed to better match overall look
  Fixed: Sometimes SHOW displays "SHOW" instead of expected text on long key press
  Fixed: Wrong CLEAR menu in PRGM and EQN mode after elaborated key combinations
  SHOW hold isn't killed by shift presses (simplifies screenshot invocation)
  SHOW hold isn't canceled by screenshot
  Fixed: Integration ends on overflow when Flag5=0 (should give an integration result) .. this also fixed a problem with restarting integration after an overflow
  Fixed: Memory corruption in EQN list (reported by Raul). Exhibit itself during EQN edit by displaying "NO EQN" on other lines and all those equations are lost.

For the full list see https://technical.swissmicros.com/dm32/firmware/history.html

For current USER MANUAL see https://technical.swissmicros.com/dm32/doc/dm32_user_manual.html

RTC Correction

approx. error : -23ppm (-2.0s/d)
Correction factor C from C = 2^20 P /(10^6 + P)
Approximations :
- C = 1.04858 P
- P = 0.953674 C
Calculated C = 24.2

Put a text file /rtccalib.cfg in root directory of FAT drive with contents:

24.2

2023

Start	Stop	Accumulated Error (s)	Rate Error (s/d)	Comments
20/07/23	22/07/23	-3.5	-2.0	First 2 days initial test. -23ppm
22/07/23	22/11/23	+17.3	+0.1	with correction 24.2 (22.9ppm) applied = slightly over-corrected?

Update January 2026

Using my python Watchcheck

Date Start	Date Check	Delta	Latest Rate Error	Average Rate Error	Comments
27/01/26		+4.4			New Period. Correction 22.9ppm
27/01/26	14/04/26	+14.8s	+0.1	+0.1	77 days +10 seconds

DM32 Info

Firmware : https://technical.swissmicros.com/dm32/firmware/
YouTube videos by NA McBee : https://www.youtube.com/@N.A._McBee/video
Swissmicros forum : https://forum.swissmicros.com/viewforum.php?f=33&sid=2185cf0ed161a970070277183ff137c0

Hardware / Firmware issue

I received the following email from Swiss Micros in 8th March 2024 explaining a hardware change that's required to early production units to ensure correct operation with the latest firmware, which allows the processing speed to increase when powered via USB (as per the DM41X and DM42).

email re: hardware mod

Dear valued customer,

We appreciate your decision to purchase the DM32 calculator.
As one of our early adopters, your support means a lot to us.

In our initial firmware versions, we restricted the CPU speed
to 48MHz due to power limitations from the CR2032 battery.
However, in upcoming firmware updates, we're introducing the ability
to switch to 160MHz when powered by USB. It's crucial to note that
upon unplugging the USB, the CPU speed must swiftly revert to 48MHz
to prevent battery voltage drop and subsequent CPU resets.

Regrettably, we've identified an issue affecting units purchased
before December 2023. In specific scenarios, the CPU speed doesn't
transition quickly enough, potentially leading to calculator resets.

This may happen upon USB disconnection if the device is engaged in
processing tasks rather than merely awaiting user input or being powered down.

All units ordered post-November 2023 have been enhanced to ensure consistent
performance. This modification entails replacing R4 with a 22k resistor
instead of the previous 100k one.

To address this issue, we offer several solutions:

If you're comfortable soldering, replacing R4 is a straightforward fix. We're happy to dispatch a replacement
resistor to you in an envelope, see https://www.swissmicros.com/product/r4-22k-resistor

Alternatively, you can send your DM32 to us, and we'll replace the resistor and return it to you promptly,
see https://www.swissmicros.com/product/rma

We anticipate a new batch of PCBs to be available in approximately three months. Once ready, we can send you
a replacement PCB. We kindly request that you return the replaced PCB to us.

https://www.swissmicros.com/product/dm32-replacement-pcb

We sincerely apologize for any inconvenience caused and appreciate your
understanding and cooperation in resolving this matter.

Thank you for your continued support and patience.

Best regards

Michael Steinmann

SwissMicros

I find the DM32 plenty fast enough running on batteries, so I'm not necessarily going to be plugging it it to boost its performance but I do want to stay up to date with firmware changes and don't want to risk any problems, so I've ordered the replacement SMD resistor and plan to swap it myself.

update 24/01/26 - I think I did the swap…. after receiving the new resistor, not sure of the date…. I'm fairly sure I did, anyway!

HP-32Sii Owner's Manual

Download from https://literature.hpcalc.org/

HP-32sii Owner's Manual : https://literature.hpcalc.org/community/hp32sii-om-en.pdf

Further Information

calculator, dm32

DM41L Info

anonymous@undisclosed.example.com (Anonymous) — Sat, 04 Apr 2026 10:33:16 +0000

←Calculator Hardware

DM41L Info

Purchase Information

Date : 26 Aug 2024
From : Swiss Micros (Direct)
Price : approx £200
Serial : 05121
Battery Change
- 26/08/24
- 04/04/26

Firmware

cp210x_universal_windows_driver.zip

Date	Serial No.	Firmware	Version	Firmware Files	Firmware Tool
26/08/24	05121	DM41	V32	dm41_32.zip	voyage_firmware_tool.zip
01/02/25	05121	DM41	V33	dm41_33.zip
21/12/25	05121	DM41	V34	dm41_34.zip	Linux, using lpc21isp

RTC

RTC is not capable of calibration/correction?
- Perhaps the HP41CX Time corr. feature works?
- Gather data on inherent time error for a period and then try to change the values via HP41CX functionality

Update January 2026

Using my python Watchcheck

Date Start	Date Check	Delta	Latest Rate Error	Average Rate Error	Comments
23/01/26		+49.6			New Period Start
23/01/26	24/01/26	+50.6	+1.0	+1.0	After 24 hours
23/01/26	26/01/26	+52.8	+1.2	+1.1	After 3 days
23/01/26	27/01/26	+53.6	+1.0	+1.1	After 4 days

Swiss Micros Info

Firmware : https://technical.swissmicros.com/voyager/firmware/
Documentation : Online HTML User Manual
Documentation : PDF Manual
Product Page : DM41L

HP-41CX Owner's Manuals

Download from https://literature.hpcalc.org

HP-41CX Owner's Manual Vol. 1 : https://literature.hpcalc.org/community/hp41cx-om-vol1-en.pdf
HP-41CX Owner's Manual Vol. 2 : https://literature.hpcalc.org/community/hp41cx-om-vol2-en.pdf
HP-41CX Quick Reference Guide : https://literature.hpcalc.org/community/hp41cx-qrg-en.pdf

Further Information

calculator, dm41l

DM41X Info

anonymous@undisclosed.example.com (Anonymous) — Mon, 13 Apr 2026 18:35:30 +0000

←Calculator Hardware

DM41X Info

Purchase Information

Date : February 2022
From : Swiss Micros (Direct)
Price : £185
Serial : 01266
Battery Swap
- 22/09/22
- 11/02/25
- 19/02/26
- 13/04/26

Firmware

Date	Serial No.	DM41X Version	DMCP Version	Firmware Files
24/05/22	01266	2.1	3.20	dmcp_flash_3.20_dm41x-2.1.zip
27/07/24	01266	2.2	3.25	dmcp_flash_3.25_dm41x-2.2.zip
21/12/25	01266	2.3	3.28	dmcp_flash_3.28_dm41x-2.3.zip

RTC Correction

approx. error +3.5s/d = +40.5ppm
Correction factor C from C = 2^20 P /(10^6 + P)
Approximations :
- C = 1.04858 P
- P = 0.953674 C
Calculated C = -42.47

Put a text file /rtccalib.cfg in root directory of FAT drive with contents:

-42.47

Update 28/5/22

After a period of observation the rate is now over-corrected. Try reducing correction to -37.5 which corresponds to a ppm error of 35.76ppm, or 3.26 s/d.

Date Start	Date Check	Accumulated Error (s)	Rate Error (s/d)	Comments
28/3/22	24/5/22		-0.1	correction applied (C=40). Uncorrected error +3.5
24/5/22				new correction C=-42.47
24/5/22	25/5/22		-0.3	new correction in wrong direction?
28/5/22			-0.3	still over-corrected. New factor: -37.5. DM41X reports this is a correction of -35.3ppm
28/5/22	31/5/22		+0.2	Now under-corrected? Difference across 3 days is only 0.5 seconds, so perhaps needs longer to reduce reaction-time-error
28/5/22	28/6/22		+0.1	Almost 1 month later. Delta 31/5/22 = -15.7s, Delta 28/6/22 = -11.6s. +4.1s in 28 days
28/5/22	8/7/22		+0.1	Delta -10.1s
28/5/22	21/9/22		+ 0.2	Delta +1.2s. Still slightly under-corrected but good enough
28/5/22	15/4/23	-7.6	+0.0	Delta -7.6s in 322 days = 0.02 s/d
15/04/23	22/11/23	+33.3	+0.2	33.3s in 221 days = 0.15 s/d

Update January 2026

Using my python Watchcheck

Date Start	Date Check	Delta	Latest Rate Error	Average Rate Error	Comments
23/01/26		+2.7			New Period: correction-35.3ppm
23/01/26	24/01/26	+2.6	-0.1	-0.1	After 24 hours
23/01/26	26/01/26	+3.0	+0.2	+0.1	After 3 days
23/01/26	27/01/26	+3.2	+0.3	+0.1	After 4 days
23/01/26	04/02/26	+5.0	+0.2	+0.2	After 12 days
23/01/26	11/02/26	+6.1	+0.1	+0.2	After 19 days

Notes

Complex Numbers

For more about the 41Z see the separate page DM41X 41z Module

I'm using the 41Z complex number module by Angel Martin to add a 4-level complex number stack. It's a bit confusing at first to get to grips with, but adds a lot of functionality to the the DM41x.

After a bit of trial and error (this is my first play with a “plug-in module” after all) I discovered the simplest way to make the keyboard function normally, and get easy access when needed to the complex functions, was to assign a USER key (usually the statistics summation key ∑+ to the 41Z module function ∑ZL.

Each press of ∑+ now temporarily modifies all the keys to access specific 41Z functions. The functions available are extensive, through the use of the SHIFT key and by multiple presses of the ∑+ (henceforth referred to as Z) key.

I drew out a diagram to show the various functions available.

Once a selection is made the keyboard switches back to its normal behaviour, so all the usual functionality is available.

Most of these are unlikely to be used often - and it's also possible to make a much narrow selection of 41Z functions and make your own USER assignments, rather than use the ∑ZL keyboard - although this might mean you block access to inbuilt functions you might want - which would mean switching out of USER keyboard mode at times. At the moment the ∑ZL option seems the most versatile.

Many of the 41Z functions available are beyond my pay grade and unlikely to ever find a use, but the Complex Keyboard still makes things much easier to deal with.

For example the two keypresses:

Z 1\x

is much easier than the 7 it would otherwise need to invert a complex number

XEQALPHAZINVALPHA I need to practice finding the right function (the main ones printed on the keyboard as well as the new ones provided by 41Z's ∑ZL keyboard, but my fingers are slowly starting to move in the right direction.

One thing I do notice, though, as that due to the need to press various keys (XEQ, ALPHA, SHIFT etc) it's sometimes possible to make a real mess if you miss a vital key in the middle of entering lots of data & instructions and find your stack totally screwed up, or several lines of program code full of nonsense….

I'm sure it'll all become second nature soon enough.

HP16C Emulator module

This is another interesting module to add the functionality of the HP16C - the Programmer's Calculator designed to handle calculations in various mathematical bases as used in computer programming and networking : Binary, Octal, Hexadecimal and Decimal. I adds much more value than the rather basic functions in the Advantage Pac module.

After much trial and error I found a combination of HP16C module and Library 4 library that worked correctly. The HP16C module needs the Library 4 module, but I found some problems with different versions. Using the versions contained in the Swiss Micros package had a weird bug - the 16* (multiplication) function simply didn't work. I found a post by Angel Martin on the HP Calculator Forum with a ZIP file containing the 2 modules that worked correctly.

Here is the zip file : hp-16c_rev.1a.zip

I'll make a separate guide to using the main features here DM41X HP16C Module

Guides

Hints & Tips

Swiss Micros Info

Firmware : https://technical.swissmicros.com/dm41x/firmware/
Documentation : Online User Manual
Documentation : PDF Manual
Product Page : DM41X

Issues

Arrived new with a speck of dirt behind the glass in front of the LCD.
- Able to remove by carefully prising the glass from its bezel (it's held in with double-sided tape)

41Z Deluxe Module

Weird behaviour with its "common factor" display

Update September 2024

The factorization error in the deluxe version has been fixed by Angel….

Swiss Micros forum discussion about the issue

the fixed version 41z_bs_2x2_2_.zip
My page DM41X 41z Module

DM41X Program Listings

See DM41X Progs

HP-41CX Owner's Manuals

Download from https://literature.hpcalc.org

HP-41CX Owner's Manual Vol. 1 : https://literature.hpcalc.org/community/hp41cx-om-vol1-en.pdf
HP-41CX Owner's Manual Vol. 2 : https://literature.hpcalc.org/community/hp41cx-om-vol2-en.pdf
HP-41CX Quick Reference Guide : https://literature.hpcalc.org/community/hp41cx-qrg-en.pdf

Page Updated : 13/04/26 19:35 BST

calculator, dm41x

DM42 Info

anonymous@undisclosed.example.com (Anonymous) — Tue, 17 Feb 2026 16:00:57 +0000

←Calculator Hardware

DM42 Info

Purchase Information

Date : December 2020
From : Swiss Micros (via Amazon)
Price : £179
Serial : 06434
Battery Swap : 21/09/24

Firmware

Date	Serial No.	DM42 Version	Free42 Version	DMCP Version	Firmware Files combined	DM42*.pgm
24/5/22	06434	3.21	3.0.9	3.22	dmcp_flash_3.23_dm42-3.21.zip	dm42-3.21.pgm
15/4/23	06434	3.22	3.0.15	3.24	dmcp_flash_3.24_dm42-3.22.bin	dm42-3.22.pgm
27/07/24	06434	3.23	3.1.8	3.25	dmcp_flash_3.25_dm42-3.23.zip	dm42-3.23.pgm
11/02/26	0644	3.26	3.3.10	3.29	dmcp_flash_3.29_dm42-3.26.zip	dm42-3.26.pgm

3rd party Firmware

DM42 restoration : dm42_pgm_qspi.zip
- DM42 pgm only (no QSPI) : dm42-3.23.zip
Generally I find C47 to be sluggish and laggy and although the features are great the User Experience is poor.
- The Dev. Team seem to spend more time adding new features/functions and don't really care that it's very slow
- Reports indicate that the DM42n runs C47 much faster

Date	Serial No.	Firmware	Version	DMCP Version	Firmware Files
21/09/24	06434	C47	0.109.02.05	3.25	C47 Release : 1 August 2024
18/02/25	06434	C47	0.109.02.07b4	3.25	C47 Release : 2 Jan 2025

RTC Correction

approx. error +3.4s/d = +39.3pm
Correction factor C from C = 2^20 P /(10^6 + P)
Approximations :
- C = 1.04858 P
- P = 0.953674 C
Calculated C = -41.26

Put a text file /rtccalib.cfg in root directory of FAT drive with contents:

-41.26

2022

Start	Stop	Accumulated Error (s)	Rate Error (s/d)	Comments
28/3/22	7/11/22	-5.8	0.0	-5.8s over period 224 days = -0.03s/d

Update January 2026

Using my python Watchcheck

Date Start	Date Check	Delta	Latest Rate Error	Average Rate Error	Comments
26/01/26		-43.0			Start Period. Correction -39.1ppm
26/01/26	27/01/26	-43.2	-0.3	-0.3	After 24 hours
26/01/26	04/02/26	-42.8	+0.1	+0.0	After 9 days

Swiss Micros Info

Firmware : https://technical.swissmicros.com/dm42/firmware/
Documentation : Online HTML User Manual
Documentation : PDF Manual
Product Page : DM42

HP-42S Owner's Manuals

Download from https://literature.hpcalc.org

HP-42S Owners's Manual : https://literature.hpcalc.org/community/hp42s-om-en.pdf
HP-42S Programming Examples & Techniques : https://literature.hpcalc.org/community/hp42s-prog-en.pdf

DM42 Program Listings

See DM42 Progs

calculator, dm42

HP-11C Info

anonymous@undisclosed.example.com (Anonymous) — Tue, 17 Feb 2026 16:31:18 +0000

←Calculator Hardware

HP-11C Info

Purchase Information

Date : 24/7/22
From : eBay
Price : £63.49
Serial : 2219AO3710

Notes

Bought on eBay as a first, relatively cheap, vintage HP Voyager model. Some of the keys are a little vague feeling, although always registering positively and never missing a key-press (unlike the Swiss Micro DM15L which occasionally misses a key-press if it's not performed with enough pressure).

I like the old feel, and although it's noticeably slower than more modern calculators, it has plenty of useful features and functions to be carried and used when the higher power or features of the DM42, DM41X or DM15L are not needed.

Guides

Hints & Tips

Issues

HP-11C Owner's Handbook

Download from https://literature.hpcalc.org

HP-11C Owner's Handbook & Problem-Solving Guide : https://literature.hpcalc.org/community/hp11c-oh-en.pdf

HP11C Program Listings

See HP11C Progs

Page Updated : 17/02/26 16:31 GMT

calculator, hp11c

HP-35s Info

anonymous@undisclosed.example.com (Anonymous) — Tue, 17 Feb 2026 16:28:57 +0000

←Calculator Hardware

HP-35s Info

Purchase Information

HP35s #1

Date : December 2020
From : Amazon
Price : £46
Serial : PHA9150B2C
New Batteries
- Jan 2022
- Mar 2024

HP35s #2

Date : December 2020
From : Calculators Direct
Price : £46
Serial : PHA9150KFF
New Batteries
- Jan 2022
- Feb 2024
- Jan 2026

The HP35s

I have two of these - one for the workshop/shed and one for general use. I try to keep them programmed with the same functions mostly.

The HP35s is a useful RPN programmable scientific calculator, with a few annoyances, but I'm glad I've got a couple lying around to play with. Of course it's not possible to interface a computer with the HP35s, so I have no electronic records of my programs. I write everything down in a notebook, in case I need to re-enter it later, but sharing it online isn't quite as straightforward as with the SwissMicros calculators.

HP35S Program Listings

See HP35s Progs

HP-35s User's Guide

Download from https://literature.hpcalc.org

HP-35s User's Guide : https://literature.hpcalc.org/official/hp35s-ug-en.pdf

calculator, hp35s

Calculator Hardware

anonymous@undisclosed.example.com (Anonymous) — Tue, 17 Feb 2026 17:48:55 +0000

←Calculators

Calculator Hardware

— John Pumford-Green 24/04/23 16:19

Further Information

calculator

John's Vademecum - public:calculator:info

DM15L Info

DM15L Info

Purchase Information

Firmware

Upgrade firmware on Linux

bash scripts

Upgrade firware on Windows

Serial USB Driver for Windows

Windows Firmware Upload Tool

Swiss Micros Official

Swiss Micros Firmware files

LF15C - 3rd Party Firmware

DESK-15 - 3rd Party Firmware

RTC Error

Update January 2026

Swiss Micros Info

HP-15C Owner's Handbooks

DM15L Memory Dumps and Program Listings

DM16L Info

DM16L Info

Purchase Information

Firmware

RTC Error

Swiss Micros Info

HP-16C Owner's Handbook

DM15L Memory Dumps and Program Listings

DM32 Info

DM32 Info

Photos

Purchase Information

Firmware

Changes

DM32 v2.11: 2025-12-05

DM32 v2.10: 2024-08-17

DM32 v2.09: 2024-05-06

DM32 v2.08: 2024-03-18

DM32 v2.07: 2023-12-08

DM32 v2.06: 2023-11-01

RTC Correction

2023

Update January 2026

DM32 Info

Hardware / Firmware issue

HP-32Sii Owner's Manual

Further Information

DM41L Info

DM41L Info

Purchase Information

Firmware

RTC

Update January 2026

Swiss Micros Info

HP-41CX Owner's Manuals

Further Information

DM41X Info

DM41X Info

Purchase Information

Firmware

RTC Correction

Update 28/5/22

Update January 2026

Notes

Complex Numbers

HP16C Emulator module

Guides

Swiss Micros Info

Issues

41Z Deluxe Module

Module files that work (for me)

Update September 2024

DM41X Program Listings

HP-41CX Owner's Manuals

DM42 Info

DM42 Info

Purchase Information

Firmware

3rd party Firmware

RTC Correction

2022