2019-07-22 Linux Allow User Program Access Serial Port

When I access the com port, I got the access denied if not in root permission.
To allow my user-mode program to access the serial port, I need to add my account into the dialout group.

Solution

Check COM port used

jk@ubuntu:~/code/hello-arm$ dmesg | grep tty
[    0.004000] console [tty0] enabled
[    2.773990] 00:05: ttyS0 at I/O 0x3f8 (irq = 4, base_baud = 115200) is a 16550A
[    2.836452] 00:06: ttyS1 at I/O 0x2f8 (irq = 3, base_baud = 115200) is a 16550A

Open Terminal and type:
- ```
ls -l /dev/ttyS* 
```
Now we just need to add our user to the group:
- ```
sudo usermod -a -G dialout $USER
```
We needs to log out and log in again for this change to take effect.

Check users in dialout group

getent group dialout
dialout:x:20:jk
jk@ubuntu:~/code/hello-arm$

References

[1], /dev/ttyUSB0 permission denied 解決辦法：永久有可操作權限, https://blog.csdn.net/w383117613/article/details/44216653, (2015-03-12)
[2], First time set up- permission denied to usb port- ubuntu 14.04, https://arduino.stackexchange.com/questions/21215/first-time-set-up-permission-denied-to-usb-port-ubuntu-14-04, (2016-02-29)
[3], 這問題(USB TO RS232)不知該到哪問? [論壇 - Ubuntu硬體支援], https://www.ubuntu-tw.org/modules/newbb/viewtopic.php?viewmode=compact&order=DESC&topic_id=38018&forum=3, (2013-07-03)

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2019-07-22 Linux Allow User Program Access Serial Port

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