SeaLogHeinrichs Weikamp
How to import dives from a Heinrichs Weikamp OSTC Mk2
The Heinrichs Weikamp OSTC Mk2 transfers over serial cable only. iOS does not expose that kind of connection to apps, so the dives come across once through a Mac or PC, then live on your phone forever.
Transfer the dives off the Heinrichs Weikamp OSTC Mk2
- Install the driver for the cable
The serial cable is a USB-to-serial adapter, and its chipset needs a driver before any software can see the Heinrichs Weikamp OSTC Mk2. Install the FTDI (legacy USB generation: OSTC 1, OSTC Mk.2, OSTC 2N, OSTC 2C). The Bluetooth generation needs no driver at all: pairing creates a virtual COM / SPP serial port that software talks to directly. driver, then reboot. Skip this and the desktop app will report no device on a cable that is working perfectly.
These cables are USB-to-serial. Without the FTDI driver the port never appears, and the software reports no device. - Connect the Heinrichs Weikamp OSTC Mk2 to a Mac or PC
Use the serial cable made for the Heinrichs Weikamp OSTC Mk2, not a generic charging cable: the data pins differ. Check the o-ring is seated, line the connector up with the notch on the case, and turn it to lock. An iPhone or iPad cannot open this kind of connection at all, so this step has to happen on a computer.
The o-ring must be in place, the nub lines up with the notch, then the head turns a quarter turn to lock. This cable is FTDI (legacy USB generation: OSTC 1, OSTC Mk.2, OSTC 2N, OSTC 2C). The Bluetooth generation needs no driver at all: pairing creates a virtual COM / SPP serial port that software talks to directly.. - Put the computer into PC mode
Switch the Heinrichs Weikamp OSTC Mk2 into its PC or upload mode before you launch the software, not after. Most desktop apps only look for the unit at startup, so a computer that wakes up late is a computer the software never finds.
Most units only hold this mode for a minute or two, so do it last, right before you connect. - Download the dives with desktop software
Read the computer with OSTC Companion and Subsurface or Subsurface. Subsurface is free, open source, runs on macOS, Windows and Linux, and supports this model.
Subsurface (the logbook Heinrichs Weikamp's own manuals point you to)
- Export the dives as UDDF
Export the whole logbook to a UDDF file. UDDF is the open dive-log exchange format and keeps the full depth profile, not just the summary numbers.
Export the whole logbook, not the visible page. UDDF keeps the sample-by-sample depth profile, which a summary CSV does not. - Import the file into SeaLog
Get the file to your phone. AirDrop, iCloud Drive or email all work, anything that lands it in the iOS Files app. Then in SeaLog tap the plus button, Import dives, UDDF file, and pick it. Every dive arrives with its profile, and duplicates are skipped.
A dive log app for the OSTC Mk2
Once the dives are in, SeaLog treats them like its own: a scrubbable depth profile, the site pinned on a map, water temperature, gas and tank, buddies, and the photos from your camera roll matched to the minutes you were underwater. Tag the animals you saw and they go into your species life list. It works offline on the boat and syncs when you are back, and your whole logbook exports to UDDF, CSV or PDF whenever you ask, so nothing is locked in here either.
Heinrichs Weikamp’s own software and drivers
Alive and actively maintained (the company rebranded to "hw diving", heinrichsweikamp.com now redirects to hwdiving.com, and the OSTC Companion installers were rebuilt in October 2025), but it has never shipped a logbook program of its own, so the actual dive-to-file step always happens in third-party software, above all Subsurface, which the OSTC manuals name explicitly.
- Desktop softwareSubsurface (the logbook Heinrichs Weikamp's own manuals point you to)Third-party and free, but the OSTC manuals name it as the way to read out dives and even push firmware; it is also the practical route to a UDDF or CSV export file.Win + Mac
- FirmwareFirmware v3.16 for the legacy USB modelsFinal firmware line for the cable generation, separate from hwOS entirely.
- FirmwareBootloader V2Recovery bootloader for the cable generation; needed when a normal firmware upload has left the unit unresponsive.Windows
- ManualOSTC 2C, OSTC 2N and OSTC Mk.2 manual (English)The older-generation manual; documents the 0000 pairing code and the virtual COM port the desktop software connects through.
- Official guideConnection and firmware-update walkthrough on the official OSTC forumThe thread the manuals and FAQ both link to, covering the port setup and update flow for OSTC Companion, Subsurface, HWOS Config and OSTConf.Win + Mac
- Supporthw diving firmware and software downloads (English)The brand's only real downloads hub: every firmware image, OSTC Companion and the bootloaders, each labelled with the models it covers.
- Supporthw diving FAQ: pairing, COM ports and phone connections (English)Where to find the assigned COM port on Windows, the tty.OSTC…-SPP naming on macOS, and why an iPhone will never show the OSTC in Bluetooth settings.Win + Mac
- SupportOfficial OSTC user forumRun by the manufacturer and the main place connection problems get diagnosed, including the recurring FTDI driver breakage on Windows.
Every link goes to Heinrichs Weikamp’s own site and was checked before publishing. If one has rotted since, tell us and we will fix it.
Heinrichs Weikamp OSTC Mk2: common questions
Can I connect the Heinrichs Weikamp OSTC Mk2 to my iPhone directly?
No, and no app can change that. The Heinrichs Weikamp OSTC Mk2 transfers over serial cable only, a connection iOS does not expose to apps. Anyone promising a direct wireless download from this model is describing a different computer. The one-time cable route above gets every dive across.
Which cable and drivers do I need on a Mac?
Use the Heinrichs Weikamp interface cable made for this model, not a generic charging cable: the data pins differ. Most of these cables are USB-to-serial and need the driver for their chipset on macOS, usually Silicon Labs CP210x or FTDI. Install the driver, reboot, and the port appears to the desktop software.
Do I have to do this every time I dive?
Only if you want the new dives in digitally. Many divers do the cable run once to rescue their history, then log new dives directly in SeaLog on the boat, which takes about as long as filling in a paper page.