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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 is also simple. Start Vivado, new project, build, export to SDK, add FSBL, build BOOT.BIN, adding u-boot.elf. Done. Works first try.

Step 2: Does the LED work too?

cd /sys/class
cd leds

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And failed again, there are no LEDs available. They are missing in device-tree. Let's add the LED then to the device-tree. This can be done with utility called DTC. To my big surprise this tool is not at all available for Windows PC. Help... A few hours later I have DTC executable that works on Windows. My coworker who made it possible sends win32 patches to the maintainers of DTC tool, and I add the DTC.EXE for free downloads.

Zedboard OOB Design

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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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