Audio Interfaces - Quectel M35 User Manual

The following circuit shows a reference design for the communication between module and PC. Since the
electrical level of module is 2.8V, so a RS-232 level shifter must be used. Note that you should assure the
IO voltage of level shifter which connects to module is 2.8V.
Module
Please visit vendor web site to select the suitable RS-232 level shifter IC, such as: http://www.exar.com/
and http://www.maximintegrated.com.
3.8.

Audio Interfaces

The module provides two analogy input channels and two analogy output channels.
Table 9: Pin Definition of Audio Interface
Interfaces
AIN1/AOUT1
AIN2/AOUT2
M35_User_Manual
C1+
C1-
C2+
C2-
1K
T1IN
DCD
1K
TXD T2IN
1K
CTS T3IN
1K
T4IN
RI
T5IN
/R1OUT
5.6K
1K
RXD
R1OUT
1K
DTR R2OUT
1K
RTS R3OUT
GND
5.6K 5.6K
RS-232 Level Shifter
Figure 23: Sketch Map for RS-232 Interface Match
Name Pin NO.
MIC1P 4
MIC1N 5
SPK1P 7
SPK1N 6
AGND 1
Confidential / Released
GSM/GPRS Module Series
V+ GND
GND GND
VCC 3.3V
V- GND
T2OUT
T1OUT
T5OUT
T3OUT
T4OUT 6
7
R1IN 8
R2IN 9
R3IN
To PC Serial Port
Description
Channel 1 Microphone positive input
Channel 1 Microphone negative input
Channel 1 Audio positive output
Channel 1 Audio negative output
Form a pseudo-differential pair with SPK2P
M35 User Manual
1
2
3
4
5
GND
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