Make camera support optional

[Ezward]

The code can be downloaded onto a normal ESP32 board, but it will crash when it attempts to initialize the camera. It would be a nice feature to be able to build without camera support so the basic rover can run on an ESP32.

• Add a preprocessor flag ENABLE_ESP32_CAMERA that must be defined for the Esp32Cam camera code to be included in the compile.
• Add and endpoint to check for camera support; if camera is supported this returns true, false otherwise
• Have the web client check the endpoint at startup and hide or show the camera controls based on the return value. Default should be to hide the camera support.

[Ezward]

I did part one of this; the c++ code now uses the preprocessor symbol ENABLE_CAMERA to enable camera support. It is defined in platformio.ini by default, so camera is enabled by default. Remove that line from platformio.ini and you should be able to download to a normal ESP32. You may want to pick a different board type in platformio.ini rather than esp32cam.

Note that if you are using a regular ESP32, you will probably have enough pins to support both the wheel encoders and the serial port. You may need a minor code change to make that work; I believe there are one or two places that will define SERIAL_DISABLE if USE_WHEEL_ENCODERS is defined; you would want to make those two symbols orthogonal.

This commit only addresses the C++ code. The Web camera UI will still be present, but non-functional. A later commit will hide the camera ui if the camera is not enabled.

[Ezward]

@cgrrty When you get a chance, please pull the latest code and let me know if this fix works on the esp32. I found a bug in the esp32cam if we turn off the camera; the encoder interrupts to not work. This can be compensated for if we also undefine USE_ENCODER_INTERRUPTS, then the encoder pins will be polled and this makes speed control and pose estimation continue to work. I don't think that will be necessary on a normal esp32; please let me know when you get a chance. Then I can close this bug.

PS: latest code hides the camera UI if the camera is disabled.

[Ezward]

@cgrrty Have you been able to build and run the code on an ESP32 yet?

[cgrrty]

Hi Ezward After trying, the compilation can be passed, and it can be run.

[Ezward]

Closing as done. Thanks.