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E4 — RFID_DMA_TX_INIT_FAILED

Hardware version

This error only occurs on v3 hardware.

The DMA transmit buffer for RFID SPI communication could not be allocated.

What happens​

rfid_task exits immediately. RFID scanning is unavailable for this session. All other firmware tasks continue normally.

Possible causes​

  • Heap memory exhaustion at startup prevented the DMA buffer allocation.
  • A firmware bug or corrupted build produced an invalid DMA configuration.

How to fix​

  1. Reboot the device — Frees memory and retries.
  2. Reflash the firmware — Flash the latest firmware using espflash with a full chip erase.
  3. Contact support — Open an issue on GitHub if this recurs consistently.