Just a heads up that I've written a C-library¹ for downloading the dives from a Sentinel rebreather.

There are (of course) some kinks yet to be ironed out, but the goal is to get this incorporated into Subsurface².

Also here is a short description on how to do it with Minicom³ (simple text-based modem control and terminal emulation program for Linux), if you absolutely positively need to get the raw data downloaded without any frills:

1. Connect the USB-cable to your laptop and the rebreather
2. Set the rebreather in download mode
3. Observe the device path of the USB-serial. This is usually /dev/ttyUSB0. You need to set the read- and write permission (as root) for the device to the user that you will run the minicom as
4. Start the minicom program in Linux terminal with the following command: minicom -b 9600 -D /dev/ttyUSB0 -w -8 -C sentinel_dives.txt. This will store the data sent from the rebreather to sentinel_dives.txt
5. In the program paste the following two characters: D0 (dee-zero). This will download the most recent dive data. If you type them one by one, then the rebreather will interpret them as two separate commands (D and 0) due to the lag between typing. For the second dive, D1 and so on.
6. When done, exit minicom with the ctrl-A Q keystrokes

You now should have all the downloaded dives in the given file.

Note that there is a limitation on how many dives are actually stored, apparently based on the combined dive time of 10h. You can download older dives than this, but they will most probably be corrupted.

Poltsi

¹ https://github.com/Poltsi/libsentinel
² http://subsurface-divelog.org/
³ You most probably need only to install it with 'dnf install minicom' or 'apt-get install minicom'