Brightness control via legacy format

[mgjm]

@weberval found support for brightness control in the python code fossasia/led-name-badge-ls32@6640ee3 and is in the process of adding support for brightness control to fossasia/badgemagic-rs#83.

This uses the 6th byte in the header field of the data_legacy_t struct. Since full brightness is defined as 0x00 it was implemented as part of the header field / magic string. But 0x10, 0x20 and 0x30 could be used for 75%, 50% and 25% brightness. Since the commit is from 2019 I would assume that this is supported by the proprietary firmware from the manufacturer.

This firmware already implements brightness control (via button press or a BLE characteristic).

• Is it by accident that both implementations decided to support 4 brightness levels?
• Would there be interest to support brightness control also via the header of the legacy format in this firmware?
• Should we think about potential additional brightness levels or are there hardware limitations and 4 is the max?

In the pull request to add brightness control to badgemagic-rs we are thinking about the best way to represent the brightness value in the human writable config file. Any feedback is welcome:
fossasia/badgemagic-rs#83 (review)

[mariobehling]

Thanks for opening this!

Is it by accident that both implementations decided to support 4 brightness levels?

I think this is how the proprietary firmware appears to do it and the brightness steps are big enough to be recognisable.

Would there be interest to support brightness control also via the header of the legacy format in this firmware?

Yes, that would be great. Please feel free to open an issue/PR.

Should we think about potential additional brightness levels or are there hardware limitations and 4 is the max?

Additional levels should be possible as far as I understand but maybe it is not so recognizable by users as the difference between levels might seem too small.

[mgjm]

One potential limitation might be the flicker-rate. Double the brightness levels would result in half the update rate. At some point the dimming will become visible as flickering. Sensitive people already perceive the flicker at full brightness (at least with the proprietary firmware, I don't know the update rate of the OSS firmware).