Try http://homeassistant:8123. If that does not help, you may be able to find the IP address of Home Assistant Yellow on your router. The URL will be http://<IP ADDRESS>:8123

The green Compute Module 4 might have gotten unseated during transportation. Open the Yellow enclosure and make sure the green PCB is seated correctly. Especially check if its well aligned with the white outline on the PCB. If the green PCB is not aligned, align it first before pressing onto the heat-sink. If the green PCB is aligned, press onto the heat-sink on the two marked spots (centered above the CPU/SoC) to snap the CM4 in place.

Make sure that the jumper JP2 is not connected. This means the jumper is only touching one of the pins, not both.

Yes: Remove power from your system, reapply power, press and hold the red button within 5 seconds. Keep the red button pressed until the yellow led starts to flash.

The Yellow now clears the data partition, which includes Home Assistant Core, the Supervisor, and any installed add-ons. Make sure that Internet connection is present at this point - the Home Assistant Operating System needs to download the Home Assistant Supervisor and Core after the data partition has been cleared. Due to the downloads, it can take a while until Home Assistant becomes accessible again.

By default, the Raspberry Pi Compute Module 4 (CM4) tries to boot from internal eMMC before trying to boot from the USB flash drive. Therefore, the Home Assistant OS Installer for Yellow will only get started if the CM4 is empty.

Home Assistant OS 8.5 or newer versions: To clean the boot files from the internal eMMC, press and hold both the red and the blue button at startup. Keep the two buttons pressed for at least 15 seconds. Now, the system should boot from the USB flash drive again.

The Zigbee/Thread (IEEE 802.15.4) radio is directly connected via serial port to the Raspberry Pi Compute Module 4 on /dev/ttyAMA1. Note that there is no /dev/serial/by-id path for this serial port as its not connected through USB. The above tty path will remain static.

Yellow has an M.2 M-Key connector which technically supports any NVMe SSD with M-Keying and length of 2230, 2242, 2260 or 2280. The Raspberry Pi CM4 has a single lane PCIe 2.0 (Gen 2.0 x1). PCIe is backwards compatible, NVMe SSDs supporting a newer generations of PCIe or more supporting multiple lanes should generally work (e.g. Samsung 970 EVO Plus MZ-V7S500BW with a PCIe Gen 3.0 x4 interface is known to work). Since the CM4 has limited connectivity, a high-end NVMe is not required. A low-cost NVMe is typically good enough.

We and the community have identified the following models to not work (exact reasons are under investigation):

  • WD_BLACK SN850X (1TB)
  • WD_BLACK SN770
  • SK Hynix BC711
  • Crucial P2 CT250P2SSD8
Usually if one model doesn't work, other models from the same product family have a high chance to be affected as well. Other models may work, e.g. the WD Blue SN570 reportedly works, Crucial P2 CT500P2SSD8 (512GB) and Crucial P5 CT1000P5SSD8 (1GB) as well. All Samsung NVMe SSDs seem to work far.