Modules/input/Usage
From MSX Game Library
Check joystick bouton example:
u8 joyStat = Joystick_Read(JOY_PORT_1); if (IS_JOY_PRESSED(joyStat, JOY_INPUT_TRIGGER_A)) { // Joystick A boutton pressed } else if (IS_JOY_PRESSED(joyStat, JOY_INPUT_TRIGGER_B)) { // Joystick B boutton pressed }