How to enable Serial Raspberry Pi 3 ???

[Fujitus]

Hi all I'm currently trying to enable the Serial on the raspberry pi 3 but when i start my python script i got his error:

Traceback (most recent call last):
File "./My_DriverDac_V3.py", line 24, in <module>
ser = serial.Serial('/dev/ttyS0', 2400)
File "/usr/lib/python2.7/site-packages/serial/serialutil.py", line 236, in __init__
self.open()
File "/usr/lib/python2.7/site-packages/serial/serialposix.py", line 272, in open
self._reconfigure_port(force_update=True)
File "/usr/lib/python2.7/site-packages/serial/serialposix.py", line 315, in _reconfigure_port
raise SerialException("Could not configure port: {}".format(msg))
serial.serialutil.SerialException: Could not configure port: (5, 'Input/output error')

To active the serial I removed "console=ttyAMA0,115200" and "kgdboc=ttyAMA0,115200", replace "#dtoverlay=pi3-disable-bt-overlay" by "dtoverlay=pi3-disable-bt-overlay" , add enable_uart=1 and do this command: sudo systemctl disable serial-getty@ttyAMA0.service. And I reboot.

I try to find why and in find this cat: /dev/ttyS0: Input/output error

If some one add a idea, pleas let my know.

[WarheadsSE]

http://elinux.org/RPi_Serial_Connection

I should point out, that all 3 of the top google responses for "serial port on raspberry pi 3" turned up good answers.