Forum › Troubleshooting › [solved] cannot use serial port

wwwlu post at 2017-2-22 19:02:56

[solved] cannot use serial port

Edited by wwwlu at 2017-2-24 17:51

I can't read the serial port of my OPI pc plus with Armbian
My python script (which works fine on lubuntu)
#!/usr/bin/env python
# -*- coding: latin-1 -*-

import serial
import os

ser = serial.Serial('/dev/ttyS0', 9600)

while True :
      data = ser.readline()
      print (data)
      if "stop" in data:
                os.system('sudo shutdown -h now')
returns :
Traceback (most recent call last):
File "off.py", line 10, in <module>
    data = ser.readline()
File "/usr/lib/python2.7/dist-packages/serial/serialposix.py", line 453, in read
    buf = os.read(self.fd, size-len(read))
OSError: Resource temporarily unavailable
I tried :
sudo minicom -D /dev/ttyS0result:
Device /dev/ttyS0 is locked.
and with:
dmesg | grep ttyi get :
[    0.000000] Kernel command line: console=tty1 root=/dev/mmcblk0p1 rootwait rootfstype=ext4 cgroup_enable=memory swapaccount=1 panic=10 consoleblank=0 enforcing=0 loglevel=7
[    0.000000] console enabled
[    0.460131] uart0: ttyS0 at MMIO 0x1c28000 (irq = 32) is a SUNXI
[    6.252629] systemd: Expecting device dev-ttyS0.device...
[    6.488254] systemd: Starting system-getty.slice.
[    6.497739] systemd: Created slice system-getty.slice.
[    6.502287] systemd: Starting system-serial\x2dgetty.slice.
[    6.511686] systemd: Created slice system-serial\x2dgetty.slice.

What can I do ?
Thanks!

wwwlu post at 2017-2-22 23:15:53

I changed the serial config using minicom and now I get :
Traceback (most recent call last):
File "off.py", line 11, in <module>
    data = ser.readline()
File "/usr/lib/python2.7/dist-packages/serial/serialposix.py", line 495, in read
    raise SerialException('device reports readiness to read but returned no data (device disconnected or multiple access on port?)')
serial.serialutil.SerialException: device reports readiness to read but returned no data (device disconnected or multiple access on port?)

ps -ef | grep tty:
root       787   7800 13:44 tty7   00:00:50 /usr/lib/xorg/Xorg :0 -nolisten tcp vt7
root      1260   10 13:44 tty1   00:00:00 /sbin/agetty --noclear tty1 linux
root      5347   10 15:09 ttyS0    00:00:00 /bin/login --
lu      536015720 15:09 pts/0    00:00:00 grep --color=auto tty


Does this mean ttyS0 is already used by root ? what should I do ?
Thanks

wwwlu post at 2017-2-22 23:40:42

Thanks JRios,

Yes I used Sudo to execute the python script.
ser.read() does not change anything
I modified script.bin but I cannot boot anymore:
stucked on "Hit any key to stop autoboot: 0"
(does not change if I hit a key)
I will burn the image again

igorpec post at 2017-2-23 00:28:47

You can't use ttyS0 since it's in use / enabled by default for serial console. On all our builds.

Use ttyS1 or other.

wwwlu post at 2017-2-23 17:50:41

It works fine with ttyS1 !!!:)

Thanks a lot Igor and JRios for your great help!

bodtx post at 2018-3-24 00:02:02

I modified script.bin but I cannot boot anymore:
stucked on "Hit any key to stop autoboot: 0"

Do you mean you did that modification or ttyS1 was available from scratch ?

bodtx post at 2018-4-3 04:58:35

I had to enable ttyS1 with armbian-config first :
then it worked!

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