This "hidden SD card reader"-thing seems to be interesting indeed.
The CP400 knows some answers like: "[SD DETECT TEST]", "[SD FORMAT TEST]", " No Card !! ", "[SD WRITE TEST]", " Card Write OK!!" a. s. o..
Seems to be able to distiguish between "PANASONIC"-, "TOSHIBA"- or "SAN DISK"-cards.
Where is my soldering iron?