With no parameter, report the current SD read position in the form “SD printing byte 123/12345.” If no file is open the response is “Not SD printing.”
With ‘S', set the SD status auto-report interval. (Requires `AUTO_REPORT_SD_STATUS`)
With ‘C’, get the currently open file’s name (and long filename if possible). Print “(no file)” if no file is open.
M27 [C] [S<seconds>]
Report the filename and long filename of the current file.
Interval between auto-reports. S0 to disable.
Report current SD status
Report SD status every 4 seconds
Stop reporting SD status
Report currently open filename