You're doing everything right, except for one small detail which is not mentioned in the IOmappings doc. I guess we should probably add it!
you need to enable level translation. In practice, this means setting another GPIO (linux gpio4) high.
echo 4 > /sys/class/gpio/export
echo out > /sys/class/gpio/gpio4/direction
echo 1 > /sys/class/gpio/gpio4/value
Thanks for your solution.
I also found the method to control TX/RX pins on Linux from:
But I still cannot receive anything when I used: cat /dev/ttyS0
I already tested the TX/RX by using the Arduino IDE.
I used another Arduino board to test it.
Galileo was connected to the Arduino board through TX/RX, and it's worked.
The PS -A after entering GPIO setting command
ttyS0 00:00:01 login
I figured out that the TX/RX and ttyS0 are worked.
If we want to get output by cat /dev/ttyS0, we need to login as a terminal console first.
I used an Arduino to enter the username and password, and it's worked.
It's pretty inconvenient... so that maybe we need to disable the ttyS0 console before building kernel?