For 3.5mm headphone jack, use the following.

The terminals below are for the tip, ring 1, ring 2 and sleeve structure.

Two terminals are located on Ring 2, so it can be used regardless of 3-pole or 4-pole.

Connect the earphone terminal as above. Due to the nature of gba sp, there are some white noises when connecting earphones.

For the GBA SP bottom shell, just make the space between the battery terminal and the battery latch as above.