Having been using ST sensors for decades, this is the first time I stumble onto this perplexing problem: there is no datasheet available!
There is a .pdf called 'datasheet', but it only documents half the registers and them very superficially. There is no example of setting up the device and reading the results. There are only hints here and there to forget about it and just use the 'driver'.
The open source driver is clearly not written with porting or reverse engineering in mind. Comments are minimal and function names like 'cook_values()' do not help. The structure of the driver is scattered among several almost identically named source files and when finally the bare metal is reached, the registers that are used are not documented (but THEY do have more sensible names).
All in all most of the functionality is still cryptic to me. I can read and write the registers and even measure the light... but only if I wait long enough (200 ms) before reading the results. Any attempt to read the registers during the measurement - including register 0x02 MAYBE containing the pollable ready-bit - messes up the measurement and the I2C interface.
Even though I now have a marginally working system, there is no way I dare to use it for anything serious. And there are a lot of similar sensors out there to choose from. I know ST is capable of providing excellent datasheets, why oh why is this sensor an exception?
