ESP32 Flash Read Error

Common Causes

💾

Corrupted Flash Memory

Flash contents can become corrupted due to interrupted writes, failed uploads, or poor power quality during flash operations.

⚙️

Incorrect Flash Settings

Wrong flash mode (e.g., QIO vs. DIO), size, or frequency in the IDE can prevent the ESP32 from reading its own firmware correctly.

🔧

Hardware Fault in Flash or ESP32 Module

Faulty onboard flash chips or a damaged ESP32 SoC can cause read failures or prevent proper firmware execution.

🔌

Power Supply Instability During Flash Access

Flash memory is sensitive to voltage dips during read/write operations. An unstable or inadequate power supply may cause intermittent or repeatable read errors.

Symptoms

Boot Fails with Flash Read Error

Serial monitor shows messages like

SPI_FLASH_READ ERROR

Invalid head of packet

or continuous reboots after startup.

Upload Completes but Code Doesn’t Run

Firmware appears to upload normally, but the board either resets repeatedly or shows corrupted output during boot.

Works with Minimal Sketch but Not with Larger Ones

Simple code may run, but sketches with more flash usage fail to boot, suggesting marginal stability or flash size setting issues.

Solutions

Check and Adjust Flash Settings in IDE

Verify the correct flash mode, frequency, and size are set in the Arduino IDE or PlatformIO. Try lowering the flash frequency (e.g., from 80 MHz to 40 MHz).

Perform a Full Erase Before Uploading

Use esptool.py or your IDE’s “Erase Flash” option to fully wipe the chip before uploading new firmware. This removes any remnants of corrupt or mismatched data.

Use a Stable Power Supply

Ensure your ESP32 is powered from a clean, <a href="/troubleshooting/issues/power/brownout-reset/">regulated 5V source with sufficient current, especially during flashing or heavy I/O operations.

Test with a Different Board

If problems persist after checking settings and power, try uploading the same code to another ESP32 to rule out hardware faults.

More Details

ESP32 Flash Read Error #

If your ESP32 fails to boot and shows flash-related errors in the serial monitor — like

SPI_FLASH_READ ERROR

Invalid head of packet

it’s likely having trouble accessing its flash memory.

This can happen due to configuration issues, corrupted flash contents, power instability, or even hardware damage.

Common Situations #

The ESP32 reboots immediately after reset or upload
Serial monitor shows cryptic errors involving SPI flash
Your code uploads fine, but never runs
Larger sketches fail while minimal ones work
Issues appear after a brownout or power loss

Why It Happens #

🧠 Corrupted Flash #

Interrupted writes or failed uploads can leave the flash in an inconsistent state. If the bootloader or firmware header is damaged, the ESP32 may reset endlessly trying to read it.

⚙️ Wrong Flash Settings #

The ESP32’s flash mode (QIO/DIO), frequency (80/40 MHz), or size must match the actual flash chip. Misconfigured settings may work intermittently or not at all.

🔧 Flash Hardware Issues #

Cheap boards may use lower-quality flash chips or may be physically damaged. Excessive reflows or ESD damage can silently kill flash reliability.

🔌 Power Instability #

Voltage dips during flashing or boot-up can corrupt reads or writes. Flash chips are sensitive to these drops, especially during high current draw like Wi-Fi startup.

How to Fix It #

✅ 1. Recheck Flash Settings in IDE
In Arduino IDE:

Go to Tools > Flash Frequency – try lowering to 40MHz
Check Flash Mode – use DIO if QIO fails
Ensure Flash Size matches your board (e.g., 4MB)

ESP32 Upload Options in Arduino IDE

✅ 2. Perform a Full Chip Erase
Using the command line:

esptool.py --chip esp32 --port COMx erase_flash

Or, in Arduino IDE:
Use the Erase Flash: All Flash Contents option before uploading.

✅ 3. Use a Stable Power Source
Unstable 5V or USB power can cause flashing errors. Use:

A known-good USB cable
A wall adapter instead of a laptop port
Capacitors near the ESP32’s 3.3V line

✅ 4. Swap Boards to Isolate Hardware
Upload the same sketch to another ESP32. If it works there, your original board may have faulty flash or a weak regulator.

Serial Monitor Example #

rst:0x10 (RTCWDT_RTC_RESET),boot:0x13 (SPI_FAST_FLASH_BOOT)
invalid header: 0x00
flash read err, 1000
ets_main.c 371

This suggests the bootloader failed to read the firmware header from flash.

Summary #

Flash read errors are frustrating but often solvable. Start with software: erase the chip and double-check settings. If problems persist, suspect power or hardware.