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LED with Xilinx Zynq

Linux on Zynq is of course useable for much more sophisticated tasks then controlling a LED, but the basic functions should also be available?

One might think. I did. But not always are the simple things to simple.

But when I tried it the first the time, it ended up in an several days long story.

Step 1: Get some Zynq based board. One my desk was a ZYNQ XC7Z7045-FFG900 based board. That should do? There is a LED on MIO7, so from hardware side, it is prepared. Getting Linux working, well that also simple. Start Vivado, new project, build, export to SDK, add FSBL, build BOOT.BIN, adding u-boot.elf. Done. Works first try.

Does the LED work too?

cd /sys/class
cd leds

and nothing, LED class is not there. Not compiled in.

Zedboard OOB Design.

The SD Card images delivered with zedboard (and available as OOB SD Card images) include a kernel 3.09 with GPIO-LEDS enabled on MIO7 with default trigger set to MMC (SD Card) activity. Writing none to LED trigger would allow direct programmatic control over MIO7 LED on zedboard (labelled LD9!). 

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