You can find the latest firmware available here.

IMPORTANT: 6.x requires the PWM kit installed, so DO NOT install 6.x on a 5.x firmware. You can always go back to 5.x afterwards, but the tones will be converted to 6.x format and so will appear corrupted when you go back to 5.x.

JX8P Manual
JX8P PWM install manual
JX8P bootloader A2 1.07
JX8P bootloader A3 1.07
JX8P 5.04
JX8P 5.05
JX8P 5.06
JX8P 5.07
JX8P 5.08
JX8P 5.09
JX8P 5.10
JX8P 6.04
JX8P 6.05
JX8P 6.06
JX8P 6.07