M28 - Start SD write

sdcard Start writing to a file on the SD card SDSUPPORT

This command starts a file write. All commands received by Marlin are written to the file and are not executed until M29 closes the file.

With ‘B1’, set an optimized binary file transfer mode. (Requires BINARY_FILE_TRANSFER)

Use M928 to log commands to a file during printing.

M28 [B1] filename

`[B1]`	Set an optimized binary file transfer mode. (Requires `BINARY_FILE_TRANSFER`)
`filename`	File name to write

Start writing to file.txt

M28 file.txt

Start binary writing to file.txt

M28 B1 file.txt