I know external sdcard does not supported officially.
But maybe someone point me to possible solution.
Fast SDcard (200x - 400x) in display module hangs during boot sequence after power up the printer.
The same sdcard works perfectly after booting without any sdcard or with slow sdcard inserted.
The same card boots successfully on hot reset !!!
bool Panel::mount_external_sd(bool on)
lcd->buzz(1000, 1100); // seconds, frequency
this->sd->disk_initialize(); // first one seems to fail, but works next time
when I power on my printer I hear 1 second buzz and it hangs.
wneh I power on my printer and during this sound quickly eject and insert sdcard it boots successfully !!