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Accessing SYNC_IN on ZedBoard and FMCOMMS4

Question asked by cigale on Sep 15, 2017
Latest reply on Mar 9, 2018 by prashanth453

Hello there,


 I need to access the SYNC_IN pin of the AD9364 embedded on a FMCOMMS4, with ZedBoard as carrier. I'm using the latest ADI Linux image (boot_2016_r2_2017_06_29).


 According to the user manual, SYNC_IN is connected to the H23 pin of the FMC connector. Yet I found in the constraints file that H23 is named gpio_sync. Then gpio_sync is routed to GPIO 45 as far as I understand the system_top.


 Going on Linux, in /sys/class/gpio, I found gpiochip906 which indicates that the GPIO offset is 906.


 906 + 45 = 951, then:

echo 951 > export

echo high > direction

But nothing is written to the pin.


 I also tried with 906 + 45 + 54 = 1005, but export fails (Device or resource busy).


 It seems that other users had the same issue, but I couldn't find a way to solve it.


Many thanks,