Driving WS2801 and similar LED controllers with BBB

Bernd Walter ticso at cicely7.cicely.de
Fri Aug 15 15:29:54 UTC 2014

On Fri, Aug 15, 2014 at 03:43:41PM +0300, Sulev-Madis Silber (ketas) wrote:
> On 2014-08-14 21:30, John-Mark Gurney wrote:
> > Sulev-Madis Silber (ketas) wrote this message on Thu, Aug 14, 2014 at 20:19 +0300:
> >> Hello.
> >>
> >> Maybe someone else works on things like this? I basically know how those
> >> are controlled, however I'm unsure what should I choose. Maybe SPI,
> >> maybe I should bitbang GPIO for clock / data? Last should work with that
> >> specific model (WS2801). Others use weird protocols (or "protocols"). I
> >> guess I should just try something. I just let people know that I'm
> >> working on that. I won't be surprised if I'm the first one to get it
> >> working.
> > 
> > I'd look at using SPI...  From what I've read on the WS2801, SPI
> > will do exactly what you need to do, and be the most straight forward
> > solution...
> > 
> Only problem is, I seem to be only one who wants to use SPI from
> userland... No documentation, no code. I hope that it even works in BBB.
> Maybe I'll try bitbanging GPIO from Perl first. That I understand fully,
> at least. And that controller seems to allow one to be sloppy or slow.

Interesting - I thought there is a userland spi driver as there is for iic.
But you can take a look into sys/dev/flash, which holds a few kernel
drivers for different SPI flash chips.
Those may help you starting with a kernel driver for your LED.

B.Walter <bernd at bwct.de> http://www.bwct.de
Modbus/TCP Ethernet I/O Baugruppen, ARM basierte FreeBSD Rechner uvm.

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