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Docs Firmware & Software Firmware Error Codes

Firmware Error Codes

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The error codes the firmware reports on the OLED and serial debug output, and what each one means.

Firmware Error Codes

When something goes wrong, the firmware does not silently keep going. It reports a short code on the OLED status line and, in the debug build, a full message over serial.

Reporting surface

SurfaceFormat
OLED status lineERR <code>
Serial (debug build)[ERR] <code>: <message>
LED (if fitted)3 fast blinks before the code repeats

Code table

CodeMeaningLikely cause
E01Radio not respondingWiring to the E22 module, or wrong SPI pins
E02Radio calibration failedPower glitch during boot, re-run calibration
E03GPS UART timeoutGPS not powered or wrong pins
E04NVS read errorCorrupt partition, run factory reset
E05OLED I2C not foundSDA/SCL swapped, or address differs from 0x3C
E06Configuration invalidBlob version mismatch, defaults loaded
E07Watchdog resetA loop overran the 3-second watchdog window
E08Low batteryVoltage below the configured cutoff, TX disabled

Recovery order

  1. Read the code and check this table.
  2. For E01, E03, E05: verify wiring before anything else.
  3. For E02, E04, E06: a factory reset clears the store and recalibrates.
  4. For E07: update the firmware; it indicates a firmware bug, not hardware.
  5. For E08: charge or replace the cell, then reset.

Non-fatal vs fatal

Most codes are non-fatal: the device keeps running with reduced function (for example, no GPS until E03 clears). E01 is fatal to beaconing because there is no radio. The OLED makes the distinction clear: fatal errors are shown continuously, transient ones clear after 10 seconds.