I've set up a Yun before to use the handshake line on pin 7 (thanks to this great forum post) and now I have a new project that I want to do something similar with the Tian. Based on the schematic, it's a similar idea: set the output, mark the output low. But so far I haven't been able to get it working. Anyone know how to adopt the following command from /etc/rc.local to the Tian?

# Added section to set the handshake line.
# GP19 is connected to D7 of the 32U4 processor.
# This requires setting GP22 high to enable the U7 level shifter.
# This GPIO is already exported.
# Then GP19 needs to be exported, set to output, and finally brought low.
echo 1 > /sys/class/gpio/gpio15/value
echo 21 > /sys/class/gpio/export
echo "high" > /sys/class/gpio/gpio21/direction
echo 0 > /sys/class/gpio/gpio21/value

This code is what I'm using now: it's the forum poster's text with my updates for the Tian.

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