pazucj
Posts: 14
Joined: Wed Dec 06, 2017 8:31 am

Read write permissions to USB FTDI

Wed Feb 14, 2018 9:04 am

Hello I have trouble with reading on

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/dev/ttyUSB0
. Writing is working but when I want to send data to USB it doesnt' receive.

on first terminal:

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    stty -F /dev/ttyUSB0 9600
    cat /dev/ttyUSB0
and echoing to /dev/ttyUSB0:

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  echo "data" > /dev/ttyUSB0
I tried also to send in Python but also doesn't receive a data.

When I put:

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ls -la /dev/ttyUSB0

crwxrwxrwx 1 root dialout 188, 0 Feb 14 08:05 /dev/ttyUSB0
How to set permissions to read/write only on /dev/ttyUSB? Thank You

User avatar
topguy
Posts: 4350
Joined: Tue Oct 09, 2012 11:46 am
Location: Trondheim, Norway

Re: Read write permissions to USB FTDI

Wed Feb 14, 2018 12:46 pm

As long as none of these command you type return with a "permission denied" error you have all the access rights your need.
You can probably verify with the command "groups" that the "pi" user is a member of the "dialout" group and therefore has both read and write access.

What is ttyUSB0 connected to ? What is in the other end ? If you echo something it just goes over the cable to whatever ii is connected to, if its not connected to anything then the data is lost and can not be read back.

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