ESP32-CAM OTA with ArduinoOTA

ESP32_CAM_OTA is a reworked version of the BasicOTA example for the ESP32-CAM.

Table of Content

• 1. Problem
• 2. Cause
• 3. Solutions in the Arduino Environment
• 4. Solutions in the PlatformIO Environement
• 5. Simplifying the use of ArduionoOTA
• 6. Last Comments and Instructions
• 7. License

1. Problem

There is a well-known problem with using the ArduinoOTA library with the AI Thinker ESP32-CAM board and its many clones. See for example BasicOTA and OTAWebUpdater fails with "abort() was called at PC 0x40136e85 on core 1" and OTA does not work on AI Thinker ESP32-CAM board.

When attempting to update the card's firmware in the BasicOTA example included in the library, the board does receive the invitation to start an upload. However, the operation is immediately interrupted and the ESP32-CAM sends the following message on its serial port.

Start updating sketch
Progress: 0%
abort() was called at PC 0x40081dd1 on core 1

The ESP32 then reboots.

2. Cause

The problem has nothing to do with the ArduinoOTA library. Its source is the memory partition in the ESP32-CAM board definition. The esp32cam.build.partition=huge_app setting in the board definition file (board.txt), specifies that most of the memory is allocated to a single app partition (3MiB in size) leaving no room for the uploaded firmware update.

3. Solutions in the Arduino Environment

There is no possibility to change the partition scheme in the IDE when the selected board is the AI Thinker ESP32-CAM, contrary to some of the other ESP32 board definitions. One work around is to modify the value of the esp32cam.build.partition setting in the boards.txt file itself. It can be found in the .../packages/esp32/hardware/esp32/2.x.x directory. It will be possible to run the BasicOTA sketch with values such as default and min_spiffs.

That solution would certainly work, but it will be necessary to edit the board definition file each time the arduino-esp32 core is updated.

The other solution is to select a different board in the Tools menu of Arduino IDE. The following choice works.

   |  Board: "ESP32 Wrover Kit (all versions)"
   |  Upload Speed: "921600"
   |  CPU Frequency: "240 MHz (WiFi/BT)"
   |  Flash Frequency: "80MHz"
   |  Flash Mode: "QIO"
   |  Flash Size: "4MB (32Mb)"
   |  Partition Scheme: "Default 4MB with spiffs (1.2MB APP/1.5MB SPIFFS")
   |  Core Debug Level: "None"
   |  PSRAM: "Enabled"

Once the ESP32 Wrover Kit (all versions) board is selected all the other values shown above are the defaults. OTA is possible with three partitions schemes:

   1. "Default 4MB with spiffs (1.2MB APP/1.5MB SPIFFS"
   2. "Default 4MB with ffat (1.2MB APP/1.5MB FATFS"
   3. "Minimal SPIFFS (1.9MB APP/190KB SPIFFS"

This is certainly the simplest approach. However, there is no assurance that it would work with all the ESP32-CAM clones currently available although the esp32wroverkit settings in boards.txt look generic enough.

4. Solutions in the PlatformIO Environement

The two solutions discussed in the previous section would certainly work with PIO. The directory containing the boards.txt file will be different, of course. On the author's Linux system, it is ~/.platformio/packages/framework-arduinoespressif32.

Changing the board definition is done in the platformio.ini file.

[env:esp32cam]
platform = espressif32
board = esp32cam

could be replaced with

[env:esp-wrover-kit]
platform = espressif32
board = esp-wrover-kit

The following substitution

[env:esp32cam]
platform = espressif32
board = esp-wrover-kit

would probably work just as well with the added advantage of confusing everyone. However, the simplest solution in PlatformIO is to explicitly specify the partition scheme to use.

[env:esp32cam]
platform = espressif32
board = esp32cam
board_build.partitions = min_spiffs.csv  ; needed for OTA

5. Simplifying the use of ArduionoOTA

The ota.h and ota.cpp files extract most of the OTA code from original BasicOTA.ino source to make it easier to add "push" OTA in other projects. This idea is stolen borrowed from Andreas Spiess (The guy with the Swiss accent on YouTube and SensorsIot on GitHub. The use of the credentials file to define the Wi-Fi settings has been extended to include the OTA settings. The file has been renamed secrets.h. The later must be created, but there is a template named, quite appropriately, secrets-template.h which can be edited to produce a valide file..

The firmware of the ESP32 must be modified to enable OTA using ArduinoOTA. Include the ota.h and ota.cpp files in the project, add a call to setupOTA() with the proper parameters in the sketch setup() function and add a call to handleOTA() in the loop() function.

If FreeRTOS is to be used or if OTA debugging is desired, please consult the original Andreas Spiess code.

6. Last Comments and Instructions

This .INO file is nothing but a long comment but it nevertheless satisfies the Arduino requirements. The true source of the project is in the file main.cpp.

Do not forget to edit the settings in secrets-template.h file and to save it as secrets.h. Without that file, the project will not compile.

If working in the Arduino programming environment, copy the ESP32_CAM_OTA directory to the sketchbook directory. The sibling directories, include, lib and test as well as the other files at the same level, including this file, are not needed.

The upload_port and upload_flags settings in platformio.ini must be edited to match the values in secrets.h in the PlatformIO programming environment.

7. License

Since this project is clearly derivative work, it can be assumed that the license under which Espressif released BasicOTA applies. However there is no copyright notice in that file. The only mention of a license is in the root directory of the Arduino core for the ESP32, ESP32-S2 and ESP32-C repository containing the four source files. There it states that the LGPL-2.1 License applies. That license is meant primarly for libraries and not a demonstration program.

There is no copyright or license information in the Andreas Spiess (SensorIoT) GitHub repository.

As for any original work found in this repository, it is released under the BSD Zero Clause (SPDX: 0BSD) licence.

(c) Copyright, 2022, Michel Deslierres