Linux Keyer

Source code: ebkey.c.

Compile with 

gcc -std=gnu99 -Wall -O3 -o /usr/local/bin/ebkey ebkey.c -lcurses
If you get a complaint about ncurses, you'll have to do 
apt-get install libncurses5-dev
The command ebkey -? gives you a summary of the command syntax.

PC RS232

The keyer will drive built-in serial ports or USB serial ports.

Raspberry Pi GPIO

GPIO pin numbers do not correspond to the GPIO output numbers. ebkey expects the output number not the pin number. GPIO Pins. 
apt-get install ntp

ntpq -p

# Send a 12 character message with 0.1 second symbols using GPIO output 7 (pin 14 on model A and B)
# Start at next round 5 minutes and repeat every 5 minutes
echo 'test message' | ebnaut -et -N12 -p8K19A | ebkey -S0.1 -m rp,gpio=7 -T +300 -r 300 -v