User's Manual

1. Check if the speaker and the lead are well, and soldering is well;
2. Check if the relevant components have soldering problems;
3. Replace with new speaker, and verify again;
4. If you still have not found the problem, then check whether the U1 chip has soldering
or performance problems or not.
5.7. Earphone function abnormity
F9 earphone is sharing one interface with headphone JACK.
Earphone Detection: when the headset is plugged into the phone, headmic_in signal changes from high
level to low level, and CPU will treat it as “earphones plugged”, and a earphone mark will displayed
accordingly.
Headset microphone on-hook and off-hook principle: generally, there is a hook button on the earphone.
Press the button, then MIC will short-circuit to ground, ADC signal changes from high level to low level,
when the signal is detected as low, and the phone is on incoming call state, then answer the call; if the
phone is on answering call state, then end the call.