On Fri 2019-06-28 13:30:30, David Laight wrote: > From: Linus Walleij > > Sent: 28 June 2019 09:46 > ... > > A problem with LEDs is that it invites bikeshedding because it is too > > relateable. > > Bikeshedding leds :-) > > It also isn't at all clear how to handle bi-colour and tri-colour leds. > ISTR the usual interface lets you set the brightness, but more often > leds are single brightness but multi-colour. > Eg the ethernet 'speed' led which is (usually) off/orange/green. > > Changing the brightness either means changing the current or using PWM. > Both really require more hardware support than changing colours. > > I've done some led driving (for a front panel) from a PLD (small FPGA). > As well as the obvious things I did: > - dim: 1/8th on at 80Hz. > - flash: 1/8th on at 4Hz. > - orange: 50-50 red-green at 80Hz on an RGB led. > > There was also the 'ethernet activity' led which could either be driven > by the hardware, or forced on/off/flash by the driver. > If driven by the hardware, the software could read the current state. > > None of this really fitted the Linux leds interface. Well, we are working on some of those :-). But lets discuss that in separate threads. In particular we are working on triggers and RGB LEDs. bi-color LEDs seem to handled as two separate LEDs. Not much expected to change there. Pavel -- (english) http://www.livejournal.com/~pavelmachek (cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
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