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E21 — LCD_FRAMEBUFFER_ALLOC_FAILED

Hardware version

This error only occurs on v4 hardware.

The heap allocation for the OLED framebuffer failed.

What happens​

lcd_task exits immediately. The display will show nothing for this session. All other firmware tasks (RFID, Wi-Fi, WebSocket) continue normally.

Possible causes​

  • Not enough contiguous heap memory was available to allocate the framebuffer. This can happen if heap fragmentation from a previous crash left the heap in a degraded state.

How to fix​

  1. Reboot the device — A clean boot resets the heap. This almost always resolves a one-off allocation failure.
  2. Update the firmware — Newer firmware versions may reduce peak heap usage.
  3. Contact support — If this error appears on every cold boot with the latest firmware, open an issue on GitHub.