Hi
Thank you for your reply, and the book's title!
I checked table of contents of the book.
Maybe, The Chapter 6 is that?
I have experiences to control GPIO by python, and configure the device tree's defualt setting, write to value&direction file.
I changed the GPIO Pin setting of device tree file to out&High for the LED turn on when bbb is powered on.
But I can't find the method to turn off the LED in a few seconds. I tried to write python script to turn off the LED, and Systemd run the service script( using the After setting is "generic-board-startup.service ).
but the timing is over 1minutes from the bbbw is powered on!
I'm looking for the information of "as soon as bbb is powered on".
I'm not familiar with embedded Linux. In particular, I have little idea about the behavior of driver-related programs. I'm wondering if the driver's program should do this.