Pi4 HDMI diagnostics screen
The Pi4 has a writable EEPROM. This allows fixing firmware problems and adding new features without releasing new hardware. This wasn’t possible with previous models and you can search for “Known problems” for some examples of unfixable bugs in earlier models.
Recently the Pi4 firmware got a new feature named the HDMI diagnostics screen introduced by this commit. The 640x480 output shows the Raspberry Pi4’s available memory as well as a bunch of other useful information once a Pi4 is unable to boot beyond the eeprom boot stage:
| Line | Description |
|---|---|
| bootloader | The bootloader version and release date. |
| board | Board revision, device serial (in hexadecimal notation) and Ethernet MAC address. |
| boot |
mode: Boot mode. 6 is SPI. order describes the boot order (see BOOT_ORDER) as well as RSTS register content. 1020 in that case means cold boot (so power was added instead of rebooting from an installed OS). |
| SD CID | SD card identifier. Can be read from a running system in /sys/block/mmcblk0/device/cid. |
| part | Describes the detected partition table type (mbr) as well as detected partitions within the partition table (with type:offset). |
| fw | Filenames of startx and fixup.dat, if detected. |
| net | Link status (up/down) as well as IP configuration retrieved by DHCP: IP (ip), subnet (sn) and default gateway (gw) |
| tftp | Not sure. Probably configured TFTP server IP address. |
The QR code points to https://www.raspberrypi.org/downloads/.
Contributions welcome. The eeprom update will end up in the next version of the info-beamer hosted OS. The current version in stable doesn’t have this feature yet.