How to save a bit sequence from oscilloscope?
As stated on page 4 of the user manual for your ISDS205A scope, that model does not include the optional logic analyser functionality, which would be the usual way of capturing the digital representation of the waveform.

The manufacturer claims that it does include a "Data Recorder", which is described in the "Data Recorder.pdf" manual. That document is currently available within this 21MB zip file (although the link might change with later software versions) on the "Software and Driver Download" page.

However, from their description, this "Data Recorder" seems to be the streaming ADC output (i.e. capturing the digitised analog voltage). This is probably what you described as the "RAW voltage" capture and seems to be the best you can do with that scope.

Alternatively, buy a cheap USB logic analyser (many of those sold are similar to the Cypress FX2-based option fitted to other models of that scope) and use the Sigrok open-source software to control it.