Frequently asked questions

Why don’t my devices pair when using a Raspberry Pi 4?

When the adapter is plugged directly into the Raspberry Pi 4 it could be that devices refuse to pair. This is because there is too much interference. Connnecting the adapter through a USB extension cable should fix this issue.

What does and does not require repairing of all devices?

Requires repairing

You need to re-pair all you devices when:

Doesn’t require repairing

You don’t need to re-pair your devices when:

Help, Zigbee2mqtt fails to start!

Most of the times this is caused by zigbee-herdsman not being able to communicate with your adapter (e.g. CC2531).

Verify that you put the correct port in configuration.yaml

Execute the following command to find out the correct path:

pi@raspberry:/ $ ls -l /dev/serial/by-id
total 0
lrwxrwxrwx. 1 root root 13 Oct 19 19:26 usb-Texas_Instruments_TI_CC2531_USB_CDC___0X00124B0018ED3DDF-if00 -> ../../ttyACM0

In this example the correct port would be /dev/ttyAMC0.

Verify that the user you run Zigbee2mqtt as has write access to the port

This can be tested by executing: test -w [PORT] && echo success || echo failure (e.g. test -w /dev/ttyACM0 && echo success || echo failure).

If it outputs failure. Assign write acces by executing: sudo chown [USER] [PORT] (e.g. sudo chown pi /dev/ttyACM0).

In case of a CC2530 or CC2513 adapter, verify that don’t have a CC2540

The CC2540 can be confused easily with the CC2531 as it looks (almost) exactly the same. However, this device does not support zigbee but bluetooth. This can be verified by looking at the chip.

ModemManager is installed

ModemManger, which is default installed on e.g. Ubuntu, is known to cause problems. It can easily be fixed by removing ModemManager through sudo apt-get purge modemmanager.

I read that zigbee2mqtt has a limit of 20 devices, is this true?

Definitely not! Example given: the default Zigbee2mqtt CC2531 firmware indeed supports 20 devices connected directly to the coordinator. However, by having routers in your network the network size can be extended. Probably all AC powered devices e.g. bulbs serve as a router, you can even use another CC2530/CC2531 as a router (which has a limit of 21 devices).


When using the default Zigbee2mqtt CC2531 coordinator firmware + 2 CC2531 routers your device limit will be: