Re: gpsd blocks ttyUSB0 while using ttyACM0 on raspi

[Bo Berglund]

On Mon, 11 May 2020 02:05:08 +0200, Andreas Heertsch
<address@hidden> wrote:

>Hi
>If I run gpsd on Raspi 3B (Buster): /usr/sbin/gpsd -n -b /dev/ttyACM0 (or
>/dev/ttyS0)
>It stops communication on /dev/ttyUSB0:
>Unable to open /dev/ttyUSB0 - Device or resource busy
>If I shut down gpsd the USB-port /dev/ttyUSB0 works as expected.
>(But with the same configuration on Ubuntu and Notebook gpsd does not block
>the access to /dev/ttyUSB0)
>Can I do something better?
>Thanks Andreas

I would suggest that you ask this on the RaspberryPi forum.
https://www.raspberrypi.org/forums/viewforum.php?f=63

There may be some resource conflict inside the RPi hardware regarding
the USB serial interfaces vs the internal serial port /dev/ttyACM0.
Can also be a problem with the USB serial device driver.

You can check if there are symlinks in use just in case:
sudo ls -la /dev/tty*
crw-rw-rw- 1 root tty       5,  0 Feb 14  2019 /dev/tty
crw--w---- 1 root tty       4,  0 Feb 14  2019 /dev/tty0
crw--w---- 1 root tty       4,  1 May  7 18:35 /dev/tty1
...
crw--w---- 1 root tty       4,  9 Feb 14  2019 /dev/tty9
crw-rw---- 1 root dialout 204, 64 May  7 18:35 /dev/ttyAMA0
crw------- 1 root root      5,  3 Feb 14  2019 /dev/ttyprintk
crw-rw---- 1 root dialout 188,  0 May 11 08:54 /dev/ttyUSB0
lrwxrwxrwx 1 root root 7 May 11 08:54 /dev/ttyUSB01 -> ttyUSB0

Here my GPS unit is ttyUSB0 and the internal serial port is ttyAMA0
I have set up a rule for USB serial devices so they are symlinked to a
name reflecting which physical USB connector they are plugged into so
ttyUSB0 is symlinked to ttyUSB01 since it is on connector #1 on my
RPi4 (top closest to the Ethernet connector).


-- 
Bo Berglund
Developer in Sweden