EclaireXL

I have confirm this behavior with Core7 (but strangely not always). More to this: I have SIO2SD attached to Eclaire, and when I connect the mouse to Port1, I see the display of SIO2SD, and plugging the mouse has some effect on the SIO bus.

The joystick buttons and directions must be released to move. I guess the mouse presses some direction when idle. What do you see with stick and strig in basic?

I agree I should change the firmware to still allow keyboard movement when the joystick is held on.

stick(0) = 8, strig(0) = 1

In fact, stick(0) depends on the mouse's position.