persistent storage for configuration and task information

[dhebbeker]

For the purpose of

• read/write configuration
• read/write task information
• a user shall be able the plug-in the device to a USB host (for example PC) and be able to obtain before mentioned information as text files (possibly JSON formatted)

The application layer interface requires:

• initialize storage (if necessary)
• test if a file is available at a path
• read a file at a specific path
• write a file at a specific path

Reading and writing may be split into several transactions or run as a background process. This may be outsourced in a separate issue.

References:

• Introduction video for USB capabilities on ESP32 devices
• Port of tinyusb USB tack library for ESP32
• TinyUSB for ESP-IDF application
• General Espressif page for USB solutions
• Espressif ESP-IDF example for USB MSC + serial composite USB device

Summary of objectives:

• store information to the internal persistent memory of the microcontroller module
• the microcontroller shall be able to read and write information to different "units"
• those units shall be represented to a USB host attached to the microcontroller module via USB as text files (USB MSC)
• the text files shall be provided using a file system supported by common desktop operating systems
• the information shall be formated in the text files such that it can easily be interpreted by machine and humans (for example JSON)
• targeting an ESP32S3
• based on Arduino-ESP32 framework
• using PlatformIO ecosystem

[dhebbeker]

First find a way to get the content of a file from mass storage as string, while identifying a file via a string.

https://docs.espressif.com/projects/arduino-esp32/en/latest/api/usb_msc.html

[dhebbeker]

https://github.com/espressif/arduino-esp32/blob/master/libraries/USB/examples/USBMSC/USBMSC.ino

https://github.com/adafruit/Adafruit_TinyUSB_Arduino/blob/master/examples/MassStorage/msc_esp32_file_browser/msc_esp32_file_browser.ino