Arduino Communications Device Naming with udev

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Contents 1 Summary 2 Assumptions 3 Installation 3.1 udev 4 Communication

Summary
This article covers the configuration of udev for Arduino Communication.

Summary

If you use more than one Arduino with USB or have other USB-to-Serial devices, then you may find it convenient to make the device have the same name every time you reboot or connect the Arduino. The technique here is shown for an FTDI device, but the same process can be used for just about any USB-to-Serial device that the system recognizes.

Assumptions

• You are familiar with the Linux command line
• You understand basic text file configuration methods
• You are familiar with serial communications in Linux

Installation

The drivers for the FTDI chip is included in the kernel, so it should be detected as soon as it's plugged in, and assigned to device /dev/ttyUSB[0-9]. To check where it got assigned, run:

 dmesg | grep FTDI

The output will contain a line that looks something like this:

 usb 1-4.4: FTDI USB Serial Device converter now attached to ttyUSB0

udev

It can be annoying to have to look up what /dev/ttyUSB[0-9] the device gets assigned, so it's a good idea to add a simple udev rule that creates a link to the device when it is plugged in. It used to be possible to rename the device which would leave the ttyUSB[0-9] open for other devices. If you are using a linux kernel that is old enough you can rename the device. However, the linux community has determined the link is the proper method to track the device. Below I will show both methods.

First of all, you will need to find out the serial number of FTDI chip on the Arduino. This can be achieved by running the following, assuming your device is plugged in and was assigned to /dev/ttyUSB0:

 udevadm info --attribute-walk -n /dev/ttyUSB0

Now add/create the following file:

 /etc/udev/rules.d/98-arduino.rules

For the old kernels put this in your file:

SUBSYSTEMS=="usb", ATTRS{serial}=="XXXXXXXX", ATTRS{product}=="FT232R USB UART", ATTRS{idProduct}=="6001", ATTRS{idVendor}=="0403", NAME="arduino_1"

For the new kernels put this in your file:

SUBSYSTEMS=="usb", ATTRS{serial}=="XXXXXXXX", ATTRS{product}=="FT232R USB UART", ATTRS{idProduct}=="6001", ATTRS{idVendor}=="0403", SYMLINK+="arduino_1"

Change 'ATTRS{serial}=="XXXXXXXX"' to the serial on your device and force udev to load the new rule:

 udevadm control --reload-rules

At this point, whenever you plug in the device, the device should be renamed to /dev/arduino_1 or a link created. You can rename or link more by adding more lines to the rules file and extract the serial number for each device and of course name it what ever you like. The same process can be used for other USB-to-Serial devices as well.

Communication

To communicate with the device, you can use any of the following, to name a few:

• minicom

 minicom -b 115200 -8 -D /dev/arduino_1

• screen

 screen /dev/arduino_1 115200 8N1

• picocom

 picocom -b 115200 -p n -d 8 /dev/arduino_1

• putty - gui utility

putty -serial /dev/arduino_1 -sercfg 115200,8,n,1,X

• plink - cli utility

plink -serial /dev/arduino_1 -sercfg 115200,8,n,1,X