What causes this

OTA (Over-The-Air) updates on the ESP32 can fail due to various reasons, primarily involving flash memory issues, power instability, or incorrect partition table configurations. One common root cause is an insufficient partition size for the new firmware image, leading to a ESP_ERR_NO_MEM error during the update process. This is often accompanied by a specific error message in the serial output, such as E (XXXXX) esp_image: Checksum failed. Calculated 0xYYYY expected 0xZZZZ or E (XXXXX) ota: Write failed with error 0x8007. Additionally, incorrect configurations in the partition table can prevent the update from being applied, triggering a rollback to the previous firmware version. The ESP32 IDF (IoT Development Framework) utilizes a state machine to track the OTA process, and if the new image verification fails, the state machine will automatically initiate a rollback to ensure the device remains operational.

Minimal reproduction

A minimal example to reproduce this issue involves setting up an ESP32 with a partition table that is too small for the new firmware image. Here's a basic sketch that simulates the problem:

```cpp

#include

void setup() {

Serial.begin(115200);

ArduinoOTA.begin();

}

void loop() {

ArduinoOTA.handle();

}

```

Ensure the partition table is incorrectly defined with insufficient space for OTA, for example:

```

Name, Type, SubType, Offset, Size

nvs, data, nvs, 0x9000, 0x4000

otadata, data, ota, 0xd000, 0x2000

app0, app, ota_0, 0x10000, 0x140000

app1, app, ota_1, 0x150000, 0x140000 // Too small for larger firmware

```

Expected serial output on failure:

```

E (XXXXX) esp_image: Checksum failed. Calculated 0xYYYY expected 0xZZZZ

E (XXXXX) ota: Write failed with error 0x8007

```

The fix

To resolve this, adjust the partition sizes in the partition table to ensure there is adequate space for the new firmware image. Here’s an example of a corrected partition table:

Before:

```

app1, app, ota_1, 0x150000, 0x140000

```

After:

```

app1, app, ota_1, 0x150000, 0x190000 // Increased size for larger firmware

```

Ensure that the total size does not exceed the flash memory capacity of the ESP32.

How SerialDoctor catches this

SerialDoctor reads the serial output during the OTA process and instantly identifies the root cause of the update failure. By analyzing error codes like ESP_ERR_NO_MEM and specific checksum mismatch errors, SerialDoctor provides immediate feedback on whether the partition table or image size is the culprit, allowing for rapid debugging and resolution. Visit [serialdoctor.com](https://serialdoctor.com) to learn more.

Quick checklist

• Verify the partition table configurations match your firmware size requirements.
• Ensure the ESP32 device has adequate power supply stability during the OTA process.
• Double-check for error messages in the serial output related to memory or checksum failures.
• Use SerialDoctor to quickly diagnose and understand root causes of OTA failures.
• Regularly update the ESP-IDF to incorporate the latest OTA improvements and bug fixes.

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