Table of Contents
DM15L Info
Purchase Information
- Date : September 2021
- From : Swiss Micros (direct)
- Price : £95
- Serial : 21350
- New Battery
- July 27th 2022
- July 26th 2024
Firmware
Upgrade firmware on Linux
sudo lpc21isp <firmware_file> /dev/ttyUSB0 115200 12000
Upgrade firware on Windows
Serial USB Driver for Windows
Windows Firmware Upload Tool
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
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 |
Swiss Micros Info
- 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