I had a very strange problem with the router. When I would push custom messages to the hat from the command line:
echo "Message" > /dev/ttyUSB0
I would get the last character displayed twice on the Hat. This is strange because the same thing does not happen from my desktop computer. And, I hooked up an FTDI breakoutboard to "listen in" on the Arduino's RX/TX lines and it doesn't pick up the repeated character.
My friend ben suggested I try the command:
stty < /dev/ttyUSB0
on both machines. The desktop has a bunch more flags set. I was able to fix the router problem by using this command:
stty -F /dev/ttyUSB0 -opost -onlcr -isig -icanon -iexten -echo -echoe -echoctl -echokes