[solved] cannot use serial port

wwwlu

I can't read the serial port of my OPI pc plus with Armbian
My python script (which works fine on lubuntu)

1. #!/usr/bin/env python
   
2. # -*- coding: latin-1 -*-
   
3. 
   
4. import serial
   
5. import os
   
6. 
   
7. ser = serial.Serial('/dev/ttyS0', 9600)
   
8. 
   
9. while True :
   
10.         data = ser.readline()
    
11.         print (data)
    
12.         if "stop" in data:
    
13.                 os.system('sudo shutdown -h now')
    

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returns :

1. Traceback (most recent call last):
   
2.   File "off.py", line 10, in <module>
   
3.     data = ser.readline()
   
4.   File "/usr/lib/python2.7/dist-packages/serial/serialposix.py", line 453, in read
   
5.     buf = os.read(self.fd, size-len(read))
   
6. OSError: [Errno 11] Resource temporarily unavailable

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I tried :

1. sudo minicom -D /dev/ttyS0

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result:

1. Device /dev/ttyS0 is locked.

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and with:

1. dmesg | grep tty

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i get :

1. [    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
   
2. [    0.000000] console [tty1] enabled
   
3. [    0.460131] uart0: ttyS0 at MMIO 0x1c28000 (irq = 32) is a SUNXI
   
4. [    6.252629] systemd[1]: Expecting device dev-ttyS0.device...
   
5. [    6.488254] systemd[1]: Starting system-getty.slice.
   
6. [    6.497739] systemd[1]: Created slice system-getty.slice.
   
7. [    6.502287] systemd[1]: Starting system-serial\x2dgetty.slice.
   
8. [    6.511686] systemd[1]: Created slice system-serial\x2dgetty.slice.
   

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What can I do ?
Thanks!

wwwlu

I changed the serial config using minicom and now I get :

1. Traceback (most recent call last):
   
2.   File "off.py", line 11, in <module>
   
3.     data = ser.readline()
   
4.   File "/usr/lib/python2.7/dist-packages/serial/serialposix.py", line 495, in read
   
5.     raise SerialException('device reports readiness to read but returned no data (device disconnected or multiple access on port?)')
   
6. serial.serialutil.SerialException: device reports readiness to read but returned no data (device disconnected or multiple access on port?)
   

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ps -ef | grep tty:

1. root       787   780  0 13:44 tty7     00:00:50 /usr/lib/xorg/Xorg :0 -nolisten tcp vt7
   
2. root      1260     1  0 13:44 tty1     00:00:00 /sbin/agetty --noclear tty1 linux
   
3. root      5347     1  0 15:09 ttyS0    00:00:00 /bin/login --
   
4. lu        5360  1572  0 15:09 pts/0    00:00:00 grep --color=auto tty
   

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

wwwlu

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

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

It works fine with ttyS1 !!!  

Thanks a lot Igor and JRios for your great help!

bodtx

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

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