Yes, it works fine for me.
Every "power off"command works (shutdown -p,halt -p and so on) , also pressing the power button for N seconds turns my unit off.
After doing this "via software" power off, I'm able to turn on the box using the power button.
Also, issuing (root user):
echo "ZWC" > /dev/satmgr
immediatly turns off the unit, giving me a wonderfull root file system check at first restart...
Yes, I can try to add the old "SYN\nSYN\n ", but I think that in my unit this statement will never be executed. :)
Quite strange that doesn't work in your box. Different microcontrollers?
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I have done the test that you requested, but (obviously), the statement that sends "SYN\nSYN\n" in my box hasn't been executed.