The p-sprint keyboard emulator implemented in DOSBox for PSP provides a full 114 key-set to cover all 102 keys of a pc-style keyboard.

A full documentation for this input method is available here.

Switching inputs

L + R + SELECT + DPAD DOWN = toggle between on-screen keyboard and key mappings

L + R + START + DPAD DOWN = analog stick: toggle between mouse and joystick mode

DPAD LEFT + X = Numbers and Function Keys

DPAD UP + X = Control Keys