The audio control and processing are taken care by the COBBA-GJP, which contains the audio (and RF) codec; and MAD2. MAD2 contains MCU and DSP blocks, handling and processing the audio signals.
The baseband supports three microphone inputs and two earphone outputs. The inputs can be taken from an internal microphone, a headset microphone or a handsfree-unit (PPH-1) microphone. The microphone signals from different sources are connected to separate inputs at the COBBA-GJP ASIC. Inputs for the microphone signals are differential type.
MIC1 input is used for the microphone output of a handsfree unit. The internal microphone is connected to the MIC2 input, and the MIC3 is used for the headset.
In COBBA there are also three audio signal outputs of which the dual ended (and not differential!) EAR lines are used for internal earpiece and HF lines for accessory audio output. The third audio output, AUXOUT, is used for bias supply to the headset microphone.
Input and output selection and gain control is performed inside the COBBA-GJP ASIC according to control messages from the MAD2. DTMF and other audio tones are generated and encoded by the MAD2 and transmitted to the COBBA-GJP for decoding.
BPF, Acc. Detection
Pre Filter &
Figure 23: Audio Block Diagram (version 4)
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