showdata.py : crank up the baudrate

Signed-off-by: Christoph Maier <cm.hardware.software.elsewhere@gmail.com>
showdata.py : run for 30 seconds, then return

Signed-off-by: Christoph Maier <cm.hardware.software.elsewhere@gmail.com>
showdata.py : plot only one curve, run 10 seconds

Signed-off-by: Christoph Maier <cm.hardware.software.elsewhere@gmail.com>