GSM/GPRS Module Series
M85 Hardware Design
M85_Hardware_Design Confidential / Released 44 / 88
3.8. Audio Interfaces
The module provides two analogy input channels and three analogy output channels.
Table 8: Pin Definition of Audio Interface
AIN1 and AIN2 can be used for input of microphone and line. An electret microphone is usually used.
AIN1 and AIN2 are both differential input channels.
AOUT1 is used for output of the receiver. This channel is typically used for a receiver built into a handset.
AOUT1 channel is a differential channel.
AOUT2 is typically used with earphone. It is a single-ended and mono channel. SPK2P and AGND can
establish a pseudo differential mode.
AOUT2 can also be used for output of receiver, which can be used as a single-ended channel. SPK2P
and AGND can establish a pseudo differential mode.
AOUT3 is used for loud speaker output as it embedded an amplifier of class AB whose maximum drive
power is 870mW.
All of these three audio channels support voice and ringtone output, and so on, and can be switched by
AT+QAUDCH
command. For more details, please refer to the
document [1]
.
Interface
Pin Name
Pin No.
Description
AIN1/AOUT1
MIC1P
9
Channel 1 Microphone positive input
MIC1N
10
Channel 1 Microphone negative input
SPK1P
12
Channel 1 Audio positive output
SPK1N
11
Channel 1 Audio negative output
AIN2/AOUT2
MIC2P
7
Channel 2 Microphone positive input
MIC2N
8
Channel 2 Microphone negative input
SPK2P
5
Channel 2 Audio positive output
AGND
6
Form a pseudo-differential pair with SPK2P
AOUT3
LOUDSPKP
14
Channel 3 Audio positive output
LOUDSPKN
13
Channel 3 Audio negative output
