File Open - 0x01

Open a file for reading and/or writing.

Requests must have at least READ or WRITE bit set in the Options field.
Use the SECURE bit (0x80) of the Options byte to upload a write-only file (one that cannot be downloaded or viewed). This is useful for protecting MicroPython source code on the device.
The SECURE bit is only valid when also setting the WRITE bit and either creating a new file (CREATE + EXCLUSIVE) or replacing an existing file (TRUNCATE).

Offset	Size	Frame Field	Description
5	8-bit	File System Command	File Open - 0x01
6	16-bit	Path ID	See Get Path ID - 0x1C for a description.
8	8-bit	Options	Bitfield with the following values: 0x01 CREATE: Create if file doesn't exist. 0x02 EXCLUSIVE: Error out if file exists. 0x04 READ: Open file for reading. 0x08 WRITE: Open file for writing. 0x10 TRUNCATE: Truncate file to 0 bytes. 0x20 APPEND: Append to end of file. 0x40 UNUSED: Unused, set to 0. 0x80 SECURE: Create a secure write-only file.
9-n	variable	File Name	Pathname relative to Path ID.

Offset	Size	Frame Field	Description
5	8-bit	File System Command	File open - 0x01
6	8-bit	Status	Success - 0x00
7	16-bit	File Handle	Value used to reference file in later requests. Expires and becomes invalid if not referenced for over 2 minutes.
9	32-bit	File Size	File's size or 0xFFFFFFFF if unknown.