23

If I have multiple Arduinos connected over USB to a Linux computer, and they show up as

  • /tty/ACM0
  • /tty/ACM1
  • /tty/ACM2

How can I identify which Arduino is which without connecting to them via serial connection? Is there a serial number or a unique id on the Arduino?

Thank you for your time.

Situation: Uno R3, Mega, Leonardo with /ttyACM[1,2,3]

lsusb output with devices in the order mentioned above:

...
Bus 001 Device 011: ID 2341:0043
Bus 001 Device 013: ID 2341:8036
...
Bus 001 Device 014: ID 2341:0042

lsusb -d vendor:device -vvv shows for each one

Uno

Bus 001 Device 014: ID 2341:0042
Device Descriptor:
 bLength 18
 bDescriptorType 1
 bcdUSB 1.10
 bDeviceClass 2 Communications
 bDeviceSubClass 0
 bDeviceProtocol 0
 bMaxPacketSize0 8
 idVendor 0x2341
 idProduct 0x0042
 bcdDevice 0.01
 iManufacturer 1 Arduino (www.arduino.cc)
 iProduct 2
 iSerial 220 55330313735351910141
 bNumConfigurations 1
 Configuration Descriptor:
 bLength 9
 bDescriptorType 2
 wTotalLength 62
 bNumInterfaces 2
 bConfigurationValue 1
 iConfiguration 0
 bmAttributes 0xc0
 Self Powered
 MaxPower 100mA
 Interface Descriptor:
 bLength 9
 bDescriptorType 4
 bInterfaceNumber 0
 bAlternateSetting 0
 bNumEndpoints 1
 bInterfaceClass 2 Communications
 bInterfaceSubClass 2 Abstract (modem)
 bInterfaceProtocol 1 AT-commands (v.25ter)
 iInterface 0
 CDC Header:
 bcdCDC 10.01
 CDC ACM:
 bmCapabilities 0x06
 sends break
 line coding and serial state
 CDC Union:
 bMasterInterface 0
 bSlaveInterface 1
 Endpoint Descriptor:
 bLength 7
 bDescriptorType 5
 bEndpointAddress 0x82 EP 2 IN
 bmAttributes 3
 Transfer Type Interrupt
 Synch Type None
 Usage Type Data
 wMaxPacketSize 0x0008 1x 8 bytes
 bInterval 255
 Interface Descriptor:
 bLength 9
 bDescriptorType 4
 bInterfaceNumber 1
 bAlternateSetting 0
 bNumEndpoints 2
 bInterfaceClass 10 CDC Data
 bInterfaceSubClass 0 Unused
 bInterfaceProtocol 0
 iInterface 0
 Endpoint Descriptor:
 bLength 7
 bDescriptorType 5
 bEndpointAddress 0x04 EP 4 OUT
 bmAttributes 2
 Transfer Type Bulk
 Synch Type None
 Usage Type Data
 wMaxPacketSize 0x0040 1x 64 bytes
 bInterval 1
 Endpoint Descriptor:
 bLength 7
 bDescriptorType 5
 bEndpointAddress 0x83 EP 3 IN
 bmAttributes 2
 Transfer Type Bulk
 Synch Type None
 Usage Type Data
 wMaxPacketSize 0x0040 1x 64 bytes
 bInterval 1
Device Status: 0x0000
 (Bus Powered)

Leonardo:

Bus 001 Device 013: ID 2341:8036
Device Descriptor:
 bLength 18
 bDescriptorType 1
 bcdUSB 2.00
 bDeviceClass 0 (Defined at Interface level)
 bDeviceSubClass 0
 bDeviceProtocol 0
 bMaxPacketSize0 64
 idVendor 0x2341
 idProduct 0x8036
 bcdDevice 1.00
 iManufacturer 1 Arduino LLC
 iProduct 2 Arduino Leonardo
 iSerial 0
 bNumConfigurations 1
 Configuration Descriptor:
 bLength 9
 bDescriptorType 2
 wTotalLength 100
 bNumInterfaces 3
 bConfigurationValue 1
 iConfiguration 0
 bmAttributes 0x80
 (Bus Powered)
 MaxPower 500mA
 Interface Association:
 bLength 8
 bDescriptorType 11
 bFirstInterface 0
 bInterfaceCount 2
 bFunctionClass 2 Communications
 bFunctionSubClass 2 Abstract (modem)
 bFunctionProtocol 1 AT-commands (v.25ter)
 iFunction 0
 Interface Descriptor:
 bLength 9
 bDescriptorType 4
 bInterfaceNumber 0
 bAlternateSetting 0
 bNumEndpoints 1
 bInterfaceClass 2 Communications
 bInterfaceSubClass 2 Abstract (modem)
 bInterfaceProtocol 0 None
 iInterface 0
 CDC Header:
 bcdCDC 1.10
 CDC Call Management:
 bmCapabilities 0x01
 call management
 bDataInterface 1
 CDC ACM:
 bmCapabilities 0x06
 sends break
 line coding and serial state
 CDC Union:
 bMasterInterface 0
 bSlaveInterface 1
 Endpoint Descriptor:
 bLength 7
 bDescriptorType 5
 bEndpointAddress 0x81 EP 1 IN
 bmAttributes 3
 Transfer Type Interrupt
 Synch Type None
 Usage Type Data
 wMaxPacketSize 0x0040 1x 64 bytes
 bInterval 0
 Endpoint Descriptor:
 bLength 7
 bDescriptorType 5
 bEndpointAddress 0x83 EP 3 IN
 bmAttributes 2
 Transfer Type Bulk
 Synch Type None
 Usage Type Data
 wMaxPacketSize 0x0040 1x 64 bytes
 bInterval 0
 Interface Descriptor:
 bLength 9
 bDescriptorType 4
 bInterfaceNumber 2
 bAlternateSetting 0
 bNumEndpoints 1
 bInterfaceClass 3 Human Interface Device
 bInterfaceSubClass 0 No Subclass
 bInterfaceProtocol 0 None
 iInterface 0
 HID Device Descriptor:
 bLength 9
 bDescriptorType 33
 bcdHID 1.01
 bCountryCode 0 Not supported
 bNumDescriptors 1
 bDescriptorType 34 Report
 wDescriptorLength 101
 Report Descriptor: (length is 101)
 Item(Global): Usage Page, data= [ 0x01 ] 1
 Generic Desktop Controls
 Item(Local ): Usage, data= [ 0x02 ] 2
 Mouse
 Item(Main ): Collection, data= [ 0x01 ] 1
 Application
 Item(Local ): Usage, data= [ 0x01 ] 1
 Pointer
 Item(Main ): Collection, data= [ 0x00 ] 0
 Physical
 Item(Global): Report ID, data= [ 0x01 ] 1
 Item(Global): Usage Page, data= [ 0x09 ] 9
 Buttons
 Item(Local ): Usage Minimum, data= [ 0x01 ] 1
 Button 1 (Primary)
 Item(Local ): Usage Maximum, data= [ 0x03 ] 3
 Button 3 (Tertiary)
 Item(Global): Logical Minimum, data= [ 0x00 ] 0
 Item(Global): Logical Maximum, data= [ 0x01 ] 1
 Item(Global): Report Count, data= [ 0x03 ] 3
 Item(Global): Report Size, data= [ 0x01 ] 1
 Item(Main ): Input, data= [ 0x02 ] 2
 Data Variable Absolute No_Wrap Linear
 Preferred_State No_Null_Position Non_Volatile Bitfield
 Item(Global): Report Count, data= [ 0x01 ] 1
 Item(Global): Report Size, data= [ 0x05 ] 5
 Item(Main ): Input, data= [ 0x03 ] 3
 Constant Variable Absolute No_Wrap Linear
 Preferred_State No_Null_Position Non_Volatile Bitfield
 Item(Global): Usage Page, data= [ 0x01 ] 1
 Generic Desktop Controls
 Item(Local ): Usage, data= [ 0x30 ] 48
 Direction-X
 Item(Local ): Usage, data= [ 0x31 ] 49
 Direction-Y
 Item(Local ): Usage, data= [ 0x38 ] 56
 Wheel
 Item(Global): Logical Minimum, data= [ 0x81 ] 129
 Item(Global): Logical Maximum, data= [ 0x7f ] 127
 Item(Global): Report Size, data= [ 0x08 ] 8
 Item(Global): Report Count, data= [ 0x03 ] 3
 Item(Main ): Input, data= [ 0x06 ] 6
 Data Variable Relative No_Wrap Linear
 Preferred_State No_Null_Position Non_Volatile Bitfield
 Item(Main ): End Collection, data=none
 Item(Main ): End Collection, data=none
 ......
 Endpoint Descriptor:
 bLength 7
 bDescriptorType 5
 bEndpointAddress 0x84 EP 4 IN
 bmAttributes 3
 Transfer Type Interrupt
 Synch Type None
 Usage Type Data
 wMaxPacketSize 0x0040 1x 64 bytes
 bInterval 1
Device Status: 0x0000
 (Bus Powered)

And Mega256:

Bus 001 Device 014: ID 2341:0042
Device Descriptor:
 bLength 18
 bDescriptorType 1
 bcdUSB 1.10
 bDeviceClass 2 Communications
 bDeviceSubClass 0
 bDeviceProtocol 0
 bMaxPacketSize0 8
 idVendor 0x2341
 idProduct 0x0042
 bcdDevice 0.01
 iManufacturer 1 Arduino (www.arduino.cc)
 iProduct 2
 iSerial 220 55330313735351910141
 bNumConfigurations 1
 Configuration Descriptor:
 bLength 9
 bDescriptorType 2
 wTotalLength 62
 bNumInterfaces 2
 bConfigurationValue 1
 iConfiguration 0
 bmAttributes 0xc0
 Self Powered
 MaxPower 100mA
 Interface Descriptor:
 bLength 9
 bDescriptorType 4
 bInterfaceNumber 0
 bAlternateSetting 0
 bNumEndpoints 1
 bInterfaceClass 2 Communications
 bInterfaceSubClass 2 Abstract (modem)
 bInterfaceProtocol 1 AT-commands (v.25ter)
 iInterface 0
 CDC Header:
 bcdCDC 10.01
 CDC ACM:
 bmCapabilities 0x06
 sends break
 line coding and serial state
 CDC Union:
 bMasterInterface 0
 bSlaveInterface 1
 Endpoint Descriptor:
 bLength 7
 bDescriptorType 5
 bEndpointAddress 0x82 EP 2 IN
 bmAttributes 3
 Transfer Type Interrupt
 Synch Type None
 Usage Type Data
 wMaxPacketSize 0x0008 1x 8 bytes
 bInterval 255
 Interface Descriptor:
 bLength 9
 bDescriptorType 4
 bInterfaceNumber 1
 bAlternateSetting 0
 bNumEndpoints 2
 bInterfaceClass 10 CDC Data
 bInterfaceSubClass 0 Unused
 bInterfaceProtocol 0
 iInterface 0
 Endpoint Descriptor:
 bLength 7
 bDescriptorType 5
 bEndpointAddress 0x04 EP 4 OUT
 bmAttributes 2
 Transfer Type Bulk
 Synch Type None
 Usage Type Data
 wMaxPacketSize 0x0040 1x 64 bytes
 bInterval 1
 Endpoint Descriptor:
 bLength 7
 bDescriptorType 5
 bEndpointAddress 0x83 EP 3 IN
 bmAttributes 2
 Transfer Type Bulk
 Synch Type None
 Usage Type Data
 wMaxPacketSize 0x0040 1x 64 bytes
 bInterval 1
Device Status: 0x0000
 (Bus Powered)
dda
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asked Aug 7, 2014 at 20:11
9
  • lsusb -vvv says? Commented Aug 7, 2014 at 20:31
  • Can you unplug one and see which one disappears? Commented Aug 7, 2014 at 20:35
  • 2
    Not really, i want to do this for a remote solar-powered sensor array that will be very far away for someone to do that when it reboots. Commented Aug 7, 2014 at 20:46
  • Ignacio Vasquez-Abrams - how can I map the information from lsusb -vvv to /dev/ttyACM<x> ? IS there something in the lsusb output i can parse? Thank you for the idea! Commented Aug 7, 2014 at 20:48
  • Do you have another Arduino you can compare output with? Commented Aug 7, 2014 at 23:17

8 Answers 8

8

Assuming your distro is using udev:

udevadm info --query=all --name=/dev/ttyACM0

You might need root privileges to run this(sudo / su). It will output a list of information like this:

P: /devices/pci0000:00/0000:00:1d.2/usb4/4-2/4-2:1.0/tty/ttyACM0
N: ttyACM0
S: serial/by-id/usb-Dean_Camera_LUFA_USB-RS232_Adapter_74133353537351403012-if00
S: serial/by-path/pci-.&checktime(0000,00,1,':')d.2-usb-0:2:1.0
E: DEVLINKS=/dev/serial/by-id/usb-Dean_Camera_LUFA_USB-RS232_Adapter_74133353537351403012-if00 /dev/serial/by-path/pci-.&checktime(0000,00,1,':')d.2-usb-0:2:1.0
E: DEVNAME=/dev/ttyACM0
E: DEVPATH=/devices/pci0000:00/0000:00:1d.2/usb4/4-2/4-2:1.0/tty/ttyACM0
E: ID_BUS=usb
E: ID_MM_CANDIDATE=1
E: ID_MODEL=LUFA_USB-RS232_Adapter
E: ID_MODEL_ENC=LUFA\x20USB-RS232\x20Adapter
E: ID_MODEL_FROM_DATABASE=Uno R3 (CDC ACM)
E: ID_MODEL_ID=0043
E: ID_PATH=pci-.&checktime(0000,00,1,':')d.2-usb-0:2:1.0
E: ID_PATH_TAG=pci-0000_00_1d_2-usb-0_2_1_0
E: ID_REVISION=0001
E: ID_SERIAL=Dean_Camera_LUFA_USB-RS232_Adapter_74133353537351403012
E: ID_SERIAL_SHORT=74133353537351403012
E: ID_TYPE=generic
E: ID_USB_DRIVER=cdc_acm
E: ID_USB_INTERFACES=:020201:0a0000:
E: ID_USB_INTERFACE_NUM=00
E: ID_VENDOR=Dean_Camera
E: ID_VENDOR_ENC=Dean\x20Camera
E: ID_VENDOR_FROM_DATABASE=Arduino SA
E: ID_VENDOR_ID=2341
E: MAJOR=166
E: MINOR=0
E: SUBSYSTEM=tty
E: UDEV_LOG=3
E: USEC_INITIALIZED=751387324986

This is for an Uno with modified firmware on the atmega16u2(usb to serial). The lines of interest are probably ID_MODEL_ID and ID_MODEL_FROM_DATABASE.

answered Aug 8, 2014 at 6:19
1
  • Thank you. I am using OpenWrt in this case with hotplug2 by default but I will try to switch to udev and test this. Commented Aug 8, 2014 at 9:27
7

On Ubuntu 16.04 (and maybe previous versions or other distribs too), you can do:

> ls /dev/serial/by-id

which displays (on my box where an Arduino UNO is connected):

usb-Arduino__www.arduino.cc__0043_A4139363931351318241-if00

You can easily spot the Device ID 0043 (UNO) here.

This file is actually a link to /dev/ttyACM0 in my box.

answered Jul 24, 2016 at 20:53
1
  • Use ls -la /dev/serial/by-id to see the link Commented Dec 19, 2020 at 1:47
5

You can add an alias for each. Then you know which is which. Here is a nice tutorial on how to set this up.

Here is a snippet that I wrote based on the tutorial. In the below example, I am using a FTDI RS232RL USB to Serial adapter, which I believe is what the Arduino uses too.

  1. In order to assign an alias to a USB-Serial device, we need to find some info on the device
  2. Plug in the usb. This assumes you have already install the drivers for this use be device and the device is visible when typing:

lsusb

  1. We are going to need the following a. The vendor id b. The product id c. The device serial number
  2. To do this, it takes a little bit of hunting. All your devices log entries in '/var/log/messages'.

Therefore we can read this file and find the correct USB:

grep "ftdi" /var/log/messages

You can also use "usb"

  1. This is find all messages tagged with ftdi:

  2. Next to ftdi_sio, there is a number like 1-1.2. This is the USB device

grep "usb 1-1.2" /var/log/messages

Or you can use:

dmesg | grep "usb 1-1.3"
  1. This gives us all the info we need:

USB Alias

  1. Now with the list of serial numbers in hand let’s create a UDEV ruleset that’ll make a nice symbolic link for each of these devices. UDEV rules are usually scattered into many files in /etc/udev/rules.d. Create a new file called 99-usb-serial.rules and put the following lines in there:

In this example my alias is called 'lcdbox'

SUBSYSTEM=="tty", ATTRS{idVendor}=="0403", ATTRS{idProduct}=="6001", ATTRS{serial}=="A601ERJJ", SYMLINK+="lcdbox"
  1. SYMLINK is the name of your alias. In this case my alias is lcdbox.

  2. Save the file and type

    sudo udevadm control --reload-rules

  3. Type

    ls –l /dev/lcdbox

lrwxrwxrwx 1 root root 7 Jan 1 1970 /dev/lcdbox -> ttyUSB0

  1. This shows that my lcdbox alias is mapped to ttyUSB0
answered Nov 8, 2014 at 0:32
4

This is quite easy! You have to customize the ftdi chips firmware and add an udev rule:

First, get ftdi_eeprom via apt-get or from the sources. Identify your device via lsusb and get the id:

lsusb
Bus 001 Device 005: ID 0403:6001 Future Technology Devices International, Ltd FT232 Serial (UART) IC
....

Prepare a config and make sure, that vendor_id and product_id match. Customize the strings in the Strings section to get a unique id for your device. 

vendor_id=0x0403 # Vendor ID
product_id=0x6001 # Product ID
max_power=50 # Max. power consumption: value * 2 mA. Use 0 if self_powered = true.
###########
# Strings #
########### 
manufacturer="FTDI" # Manufacturer
product="Arduino Nano" # Product
serial="arduino1" # Serial
###########
# Options #
###########
self_powered=false # Turn this off for bus powered
remote_wakeup=false # Turn this on for remote wakeup feature
use_serial=true # Use the serial number string
# Normally out don't have to change one of these flags
# BM_type_chip=true # Newer chips are all BM type
in_is_isochronous=false # In Endpoint is Isochronous
out_is_isochronous=false # Out Endpoint is Isochronous
suspend_pull_downs=false # Enable suspend pull downs for lower power
change_usb_version=false # Change USB Version
usb_version=0x0200 # Only used when change_usb_version is enabled
########
# Misc #
########
filename="eeprom.old" # Filename, leave empty to skip file writing
cbus0=RXLED#
cbus1=TXLED#

Dump the current ftdi-firmware:

ftdi_eeprom --read-eprom

This command creates ${pwd}/eeprom.old, which contains the current firmware on the ftdi. Backup this file before continuing, because during flash-eeprom the file gets rewritten. After the backup, flash the ftdi:

ftdi_eeprom --flash-eeprom myconfig.conf

Now, create an udev rule, like so

SUBSYSTEMS=="usb", ATTRS{idProduct}=="6001", ATTRS{idVendor}=="0403", SYMLINK+="$attr{serial}", OWNER="bananapi", GROUP="pi", MODE="0777"

in /etc/udev/rules.d/90-arduino-usb.rules and restart udev. 

service udev restart

Unplug and re-plug your device and try

ls -lah /dev/arduino1

Where arduino1 is the string defined under serial in the above .conf.

See also: Risks of ftdi_eeprom? - TX always high after flashing

3

I would have used a script to make an alias under /dev/ and also set group and rights on it with udev like the other answers.

But if I didn't have udev I would pipe lsusb into grep or awk, like lsusb|grep -e "idProduct".

Anyway, with udev rules or with lsusb and grep to identify USB devices, use idVendor, idProduct and iSerial in Device descriptor part of lsusb to make the proper idenification. The idVendor tells you the manufaturer, idProduct should indentify the product from the manufacturer but sometimes they use the same product id for more than one product. Lastly, if needed, the iSerial should be a unique id for each example of that product.

answered Dec 20, 2014 at 3:45
2

You can always make some kind of id print via serial in void setup(). After the certain board is connected it will send this id to your USB interface (which you are listening with some kind of daemon app on your linux box). Once you receive id you can map it to it's path 'Arduino1' : '/dev/ttyACM0', 'Arduino2' : '/dev/ttyACM1', 'Arduino3' : '/dev/ttyACM2'...etc

Be aware that when device is disconnected for some reason it can change it's physical path so you might have to remap all of them. For this case it might be good to write separate function ex: get_id() which you can call any time (not only on startup).

answered Dec 18, 2014 at 9:04
1

I'd be mighty tempted to identify some other way, like having the sketch itself respond to a special identify command, just to avoid USB's odd ways of identifying devices.

answered Nov 7, 2014 at 1:17
1

Overview

  • One way as ansi_lumen mentioned in his answer is to flash ftdi chip EEPROM to have unique serial number which then could be identified by UDEV rules.

    But turns out it won't work on cheap chinese Arduinos which instead of FTDI has CH340G chip which doesn't have EEPROM to store unique ID (CH340B should work).

  • This answer suggests to write UDEV rule with special script which asks Arduino to send its unique ID via serial. Problem with that is that you need to modify Arduino sketch and in general it's quite complex.

Identifying by port

So the easiest way I found was to use UDEV rules and identify Arduinos by the usb port (devpath) so connecting Arduino to the same port (even in nested usb hubs) will create persistent name.

TLDR setup:

Modified version of this

  1. Find Arduino idVendor and idProduct:

lsusb

You will get something like this:

...
Bus 004 Device 001: ID 1d6b:0003 Linux Foundation 3.0 root hub
Bus 003 Device 124: ID 1a86:7523 QinHeng Electronics HL-340 USB-Serial adapter
Bus 003 Device 123: ID 214b:7000 
Bus 003 Device 122: ID 1a86:7523 QinHeng Electronics HL-340 USB-Serial adapter
Bus 003 Device 121: ID 1a86:7523 QinHeng Electronics HL-340 USB-Serial adapter
Bus 003 Device 120: ID 1a40:0101 Terminus Technology Inc. Hub
...

By connecting/disconnecting Arduino find which one it is (I have 3 connected). We are looking for its ID. In my case "...ID 1a86:7523 QinHeng...". So idVendor=1a86, idProduct=7523

  1. Create new UDEV rules file:

sudo nano /etc/udev/rules.d/99-usb-serial.rules

  1. Modify idVendor and idProduct values by what you found in previous step on copy paste it in the rules file we have created:

SUBSYSTEM=="tty", ATTRS{idVendor}=="1a86", ATTRS{idProduct}=="7523", SYMLINK+="ttyUSB-arduino%s{/devpath}"

  1. Reload UDEV rules

sudo udevadm control --reload

  1. Replug Arduinos and now it will have unique name. To test it type:

ls /dev/ttyUSB*

Which will output:

/dev/ttyUSB1 /dev/ttyUSB3 /dev/ttyUSB-arduino2.1 /dev/ttyUSB-arduino2.4 /dev/ttyUSB2 /dev/ttyUSB4 /dev/ttyUSB-arduino2.2 /dev/ttyUSB-arduino3

As you can see we still get /dev/ttyUSBx as before which are always changing depending which one was connected first. But now we also have /dev/ttyUSB-arduino{port} which are always the same for same port and only for Arduinos. To analyze what "..arduino2.4" means: 2 refers to the second port of laptop and 4 to the fourth port on usb hub.

To better see it type:

lsusb -t

Output:

...
/: Bus 03.Port 1: Dev 1, Class=root_hub, Driver=xhci_hcd/4p, 480M
 |__ Port 1: Dev 5, If 0, Class=Human Interface Device, Driver=usbhid, 12M
 |__ Port 1: Dev 5, If 1, Class=Human Interface Device, Driver=usbhid, 12M
 |__ Port 2: Dev 84, If 0, Class=Hub, Driver=hub/4p, 480M
 |__ Port 1: Dev 85, If 0, Class=Vendor Specific Class, Driver=ch341, 12M
 |__ Port 2: Dev 86, If 0, Class=Vendor Specific Class, Driver=ch341, 12M
 |__ Port 3: Dev 87, If 0, Class=Hub, Driver=hub/4p, 480M
 |__ Port 4: Dev 88, If 0, Class=Vendor Specific Class, Driver=ch341, 12M
 |__ Port 3: Dev 89, If 0, Class=Vendor Specific Class, Driver=ch341, 12M
/: Bus 02.Port 1: Dev 1, Class=root_hub, Driver=ehci-pci/2p, 480M
 |__ Port 1: Dev 2, If 0, Class=Hub, Driver=hub/6p, 480M
...

By connecting/disconnecting you can see which devices are on which ports

answered Jan 2, 2020 at 15:23

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