Audio Interfaces - SimCom SIM802 HD Manual

SIM802 Hardware Design

3.10 Audio interfaces

Table 14: Audio interface signal
Name
(AIN1/AOUT1) MIC1P
MIC1N
SPK1P
SPK1N
(AIN2/AOUT2) MIC2P
MIC2N
SPK2P
SPK2N
The module provides two analogy input channels, AIN1 and AIN2, which may be used for both
microphone and line inputs. The AIN1 and AIN2 channels are identical. One of the two channels
is typically used with a microphone built into a handset. The other channel is typically used with
an external microphone or external line input. The module analogy input configuration is
determined by control register settings and established using analogy multiplexers.
For each channels, you can use AT+CMIC to adjust the input gain level of microphone, use
AT+SIDET to set the side-tone level. In addition, you can also use AT+CLVL to adjust the output
gain level of both receiver and speaker at the same time, use AT+CHFA to activate one of the two
audio channels and deactivate the other one. For more details, please refer to document [1].
Note: Use AT command AT+CHFA to select audio channel:
0— AIN1/AOUT1 (normal audio channel), the default value is 0.
1— AIN2/AOUT2(aux_audio channel) .
It is suggested that you adopt one of the following two matching circuits in order to improve
audio performance. The difference audio signals have to be layout according to difference signal
layout rules. As show in following figures (Note: all components package are 0603.) If you want
to adopt an amplifier circuit for audio, we recommend National Company's LM4890. Of course
you can select it according to your requirement.
SIM802_HD_V2.01
Pin Function
21 Microphone1 input +
20 Microphone1 input -
23 Audio1 output+
24 Audio1 output-
18 Microphone2 input +
19 Microphone2 input -
26 Audio2 output+
25 Audio2 output-
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12.01.2010