Almost certainly this. Doubt GSL has any engineers at all that can go in to see firmware sourcecode, let alone tweak it.Yes the manufacturer it is listed under is Shenzhen Lux Power Technology Co., Ltd.
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I have been wondering where the firmware is being developed too. Maybe GSL is tweaking Lux Power's software, or maybe GSL is writing it for Lux Power, or maybe GSL is delegating all work to a Lux Power team that does all of the software for them. Who knows? I don't.
If GSL has the capacity to anything directly at all, probably limited to parameters and settings…