Quectel GSM Module Audio Design Guide V3.0

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GSM Module
Audio Design Guide
GSM/GPRS Series
Version: GSM_Module _Audio_Design_Guide_V3.0
Date: 2013-05-24

www.quectel.com

GSM/GPRS Modules
GSM Module Audio Design Guide

Our aim is to provide customers with timely and comprehensive service. For any
assistance, please contact our company headquarter:
Quectel Wireless Solutions Co., Ltd.
Room 501, Building 13, No.99, Tianzhou Road, Shanghai, China, 200233
Tel: +86 21 5108 6236
Mail: info@quectel.com

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Or our local office, for more information, please visit:
http://www.quectel.com/support/salesupport.aspx

For technical support, to report documentation errors, please visit:
http://www.quectel.com/support/techsupport.aspx

GENERAL NOTES

QUECTEL OFFERS THIS INFORMATION AS A SERVICE TO ITS CUSTOMERS. THE INFORMATION
PROVIDED IS BASED UPON CUSTOMERS’ REQUIREMENTS. QUECTEL MAKES EVERY EFFORT
TO ENSURE THE QUALITY OF THE INFORMATION IT MAKES AVAILABLE. QUECTEL DOES NOT
MAKE ANY WARRANTY AS TO THE INFORMATION CONTAINED HEREIN, AND DOES NOT ACCEPT
ANY LIABILITY FOR ANY INJURY, LOSS OR DAMAGE OF ANY KIND INCURRED BY USE OF OR
RELIANCE UPON THE INFORMATION. ALL INFORMATION SUPPLIED HEREIN ARE SUBJECT TO
CHANGE WITHOUT PRIOR NOTICE.

COPYRIGHT

THIS INFORMATION CONTAINED HERE IS PROPRIETARY TECHNICAL INFORMATION OF
QUECTEL CO., LTD. TRANSMITTABLE, REPRODUCTION, DISSEMINATION AND EDITING OF THIS
DOCUMENT AS WELL AS UTILIZATION OF THIS CONTENTS ARE FORBIDDEN WITHOUT
PERMISSION. OFFENDERS WILL BE HELD LIABLE FOR PAYMENT OF DAMAGES. ALL RIGHTS
ARE RESERVED IN THE EVENT OF A PATENT GRANT OR REGISTRATION OF A UTILITY MODEL
OR DESIGN.

Copyright © Quectel Wireless Solutions Co., Ltd. 2013. All rights reserved.

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About the document
History
Revision
1.0

1.1

1.2
3.0

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Date

Author

Description

2009-11-02

Tracy Zhang

Initial version

2009-11-20

Tracy Zhang

1.
2.
3.
4.

2010-11-20

Roy Chen

1. Added a diagram of audio channel

Jerry You

1. Added reference design of audio circuit
(M1x, M95, M80).
2. Added AT command AT+QAPS.

2013-05-24

GSM Module Audo Design Guide

Added some acronym.
Added a Audio Power Amplitude manufacturer.
Added a solution to TDD noise.
Modified cover.

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Contents
About the document ................................................................................................................................... 2
Contents ....................................................................................................................................................... 3
Table Index ................................................................................................................................................... 5
Figure Index ................................................................................................................................................. 6
1

Introduction .......................................................................................................................................... 7
1.1. Summary ...................................................................................................................................... 7
1.2. Safety Information ........................................................................................................................ 7

2

Audio Circuit Design ........................................................................................................................... 9
2.1. Audio Circuit Reference ............................................................................................................. 10
2.1.1. M1x ................................................................................................................................. 10
2.1.1.1. Microphone Reference Circuit .............................................................................. 10
2.1.1.2. Receiver Reference Circuit....................................................................................11
2.1.1.3. Headset Reference Circuit ................................................................................... 13
2.1.2. M95................................................................................................................................. 13
2.1.3. Microphone Reference Circuit ....................................................................................... 13
2.1.3.1. Receiver Reference circuit ................................................................................... 14
2.1.3.2. Headset Reference Circuit ................................................................................... 14
2.1.3.3. SPK Reference Circuit.......................................................................................... 15
2.1.4. M80................................................................................................................................. 16
2.1.4.1. Microphone Reference Circuit .............................................................................. 16
2.1.4.2. Receiver Reference Circuit................................................................................... 16
2.1.4.3. Headset Reference Circuit ................................................................................... 18
2.1.4.4. SPK Reference Circuit.......................................................................................... 18
2.2. Ringtone ..................................................................................................................................... 19
2.3. Hands-free Application at Channel AIN1/AOUT1 ...................................................................... 20
2.4. Suggestion for Audio Layout ...................................................................................................... 21
2.5. TDD Noise Solution.................................................................................................................... 21
2.6. Suggestion for Mechanical Design ............................................................................................ 22
2.7. Component of SPK .................................................................................................................... 25
2.8. Component of Microphone......................................................................................................... 26

3

Description and Suggestion ............................................................................................................. 27
3.1. AT Command ............................................................................................................................. 27
3.1.1. AT+QAUDCH ................................................................................................................. 27
3.1.2. How to Modify Volume ................................................................................................... 28
3.1.2.1. AT+QMIC .............................................................................................................. 28
3.1.2.2. AT+CLVL ............................................................................................................... 29
3.1.2.3. AT+QSIDET .......................................................................................................... 30
3.1.3. Echo Algorithm ............................................................................................................... 31
3.1.3.1. Description of Par0, Par2 and Par12 ................................................................... 33
3.1.3.2. Recommended Application Field .......................................................................... 34

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4

Appendix A ......................................................................................................................................... 35

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Table Index
TABLE 1： AUDIO HARDWARE CONFIGURATION ......................................................................................... 9
TABLE 2： REFERENCE DOCUMENT ........................................................................................................... 35
TABLE 3： DESCRIPTION OF ECHO AND TDD NOISE ................................................................................ 35

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Figure Index
FIGURE 1：MICROPHONE REFERENCE CIRCUIT FOR AIN1&AIN2 ........................................................... 10
FIGURE 2: RECEIVER REFERENCE CIRCUIT FOR AOUT1 .......................................................................... 11
FIGURE 3: RECEIVER REFERENCE CIRCUIT WITH AUDIO POWER AMPLIFIER FOR AOUT1 ................. 11
FIGURE 4：SPK REFERENCE CIRCUIT FOR AOUT2 ................................................................................... 12
FIGURE 5：RECEIVER REFERENCE CIRCUIT WITH AUDIO POWER AMPLIFIER FOR AOUT2 .............. 12
FIGURE 6：HEADSET REFERENCE CIRCUIT............................................................................................... 13

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FIGURE 7：MICROPHONE REFERENCE CIRCUIT FOR AIN1&AIN2 ........................................................... 13
FIGURE 8：RECEIVER REFERENCE CIRCUIT FOR AOUT1........................................................................ 14
FIGURE 9：HEADSET REFERENCE CIRCUIT............................................................................................... 14
FIGURE 10：SPK REFERENCE CIRCUIT ...................................................................................................... 15
FIGURE 11：MICROPHONE REFERENCE CIRCUIT FOR AIN1&AIN2 ......................................................... 16
FIGURE 12：RECEIVER REFERENCE CIRCUIT FOR AOUT1...................................................................... 16
FIGURE 13：SPK REFERENCE CIRCUIT FOR AOUT2 ................................................................................. 17
FIGURE 14：SPK REFERENCE CIRCUIT WITH AUDIO POWER AMPLIFIER FOR AOUT2 ........................ 17
FIGURE 15：HEADSET REFERENCE CIRCUIT............................................................................................. 18
FIGURE 16：SPK REFERENCE CIRCUIT ...................................................................................................... 18
FIGURE 17：HANDS-FREE REFERENCE CIRCUIT AT CHANNEL AIN1/AOUT1 ......................................... 20
FIGURE 18：LAYOUT OF AUDIO .................................................................................................................... 21
FIGURE 19：FIVE ECHO PATHS..................................................................................................................... 22
FIGURE 20：MICROPHONE SOCKET DESIGN ............................................................................................. 23
FIGURE 22：SPK FREQUENCY RESPONSE................................................................................................. 25
FIGURE 23：SPK THD ..................................................................................................................................... 26

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1

Introduction

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1.1. Summary

This document provides reference and suggestion on audio circuit design and audio parameter selection
for Quectel M1x, M95 and M80 modules.

1.2. Safety Information

The following safety precautions must be observed during all phases of the operation, such as usage,
service or repair of any cellular terminal or mobile incorporating module. Manufacturers of the cellular
terminal should send the following safety information to users and operating personnel and to incorporate
these guidelines into all manuals supplied with the product. If not so, Quectel does not take on any liability
for customer failure to comply with these precautions.

Full attention must be given to driving at all times in order to reduce the risk of an
accident. Using a mobie while driving (even with a handsfree kit) cause distraction
and can lead to an accident. You must comply with laws and regulations restricting
the use of wireless devices while driving.

Switch off the cellular terminal or mobile before boarding an aircraft. Make sure it
switched off. The operation of wireless appliances in an aircraft is forbidden to
prevent interference with communication systems. Consult the airline staff about
the use of wireless devices on boarding the aircraft, if your device offers a Fight
Mode which must be enabled prior to boarding an aircraft.

Switch off your wireless device when in hospitals or clinics or other health care
facilities. These requests are desinged to prevent possible interference with
sentitive medical equipment.

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GSM cellular terminals or mobiles operate over radio frequency signal and cellular
network and cannot be guaranteed to connect in all conditions, for example no
mobile fee or an invalid SIM card. While you are in this condition and need
emergent help, please remember using emergency call. In order to make or
receive call, the cellular terminal or mobile must be switched on and in a service
area with adequate cellular signal strength.

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Your cellular terminal or mobile contains a transmitter and receiver. When it is ON ,
it receives and transmits radio frequency energy. RF interference can occur if it is
used close to TV set, radio, computer or other electric equipment.

In locations with potencially explosive atmospheres, obey all posted signs to turn
off wireless devices such as your phone or other cellular terminals. Areas with
potencially exposive atmospheres including fuelling areas, below decks on boats,
fuel or chemical transfer or storage facilities, areas where the air contains
chemicals or particles such as grain, dust or metal powders.

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2

Audio Circuit Design

M1x and M95 have two hardware audio channels except M80. Three audio channels are defined in
software. AT+QAUDCH is used to read and set the software audio channel. This chapter provides audio
interface circuit and some solutions to resolve TDD noise and ECHO issues.

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Table 1：Audio Hardware Configuration
(AIN1/AOUT1)

Module

MIC

SPK

Differential &

M1x

Internal Bias

Internal Bias

Differential &

Differential &

Internal Bias

Internal Bias

Differential &

Differential &

Differential

Internal Bias

Notes

AOUT3

SPK

SPK

Signal-end

/

Differential

/

Signal-end

Differential

Differential &

Differential

M80

3.

MIC

Differential

M95

1.
2.

(AIN2/AOUT2)

Internal Bias

M95 module has built-in class AB amplifier and also supports voice and ringtone at channel AOUT2.
M80 module supports voice and ringtone at channel AOUT2. AOUT1 and AOUT3 can also output
ringtone but via AT+QRCH=1(only used at M80).
M80 module has built-in class AB amplifier at channel AOUT3, and the maximum power is 800mW.

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2.1. Audio Circuit Reference
2.1.1.

M1x

2.1.1.1. Microphone Reference Circuit
M1x module provides electrets-microphone bias voltage for AIN1 and AIN2. Microphone reference circuit
is shown as below:

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Close to Microphone
GND

Differential layout

10pF

Module

33pF

ESD

Electret
Microphone

MICxP

10pF

33pF

MICxN

10pF

33pF

ESD

GND

Figure 1：Microphone Reference Circuit for AIN1&AIN2

Notes
1.
2.

To avoid TDD noise issue during voice, capacitors is recommended to add close to microphone and
SPK.
TVS components are used to protect microphone and receiver from ESD damage. It has to close to
audio device and audio interface.

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2.1.1.2. Receiver Reference Circuit

Close to speaker
GND

Differential layout
33pF

10pF

Module

ESD

SPK1P

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10pF

33pF

10pF

33pF

SPK1N

ESD

GND

Figure 2: Receiver Reference Circuit for AOUT1

Close to speaker
GND

Differential layout

Module

Amplifier
circuit

10pF

33pF

10pF

33pF

10pF

33pF

ESD

SPK1P

SPK1N

ESD

GND

Figure 3: Receiver Reference Circuit with Audio Power Amplifier for AOUT1

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Close to speaker
GND

Differential layout
33pF

10pF

Module

ESD

22uF

SPK2P
AGND

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Figure 4：SPK Reference Circuit for AOUT2

Close to speaker
GND

Differential layout

Module

Amplifier
circuit

10pF

33pF

ESD

C1

SPK2P
AGND

C2

10pF

33pF

ESD

GND

Figure 5：Receiver Reference Circuit with Audio Power Amplifier for AOUT2

Note
For the value of C1 and C2, please refer to input impedance of audio power amplifier.

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2.1.1.3. Headset Reference Circuit

Close to Socket
Differential
layout

GND
4.7uF
10pF

Module

33pF

MIC2N
MIC2P

ESD

68R

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22uF

SPK2P

3

10pF

33pF

4
2
1

ESD

AGND

AGND

Amphenol
9001-8905050

GND

Figure 6：Headset Reference Circuit

2.1.2.

M95

2.1.3.

Microphone Reference Circuit

M95 module provides electrets-microphone bias voltage for AIN1 and AIN2. Reference circuit for
microphone is shown as bellow:

Close to MIC

Close to Module
GND

Module

GND

10pF

33pF

10pF

33pF

GND

Differential
layout

10pF

33pF

10pF

33pF

ESD

MICxP

MICxN

Electret
Microphone
10pF

GND

33pF

GND

10pF

33pF

ESD

GND

Figure 7：Microphone Reference Circuit for AIN1&AIN2

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2.1.3.1. Receiver Reference circuit

Close to Receiver
GND

Differential layout

ESD

33pF

10pF

Module
SPK1P

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10pF

33pF

10pF

33pF

SPK1N

ESD

GND

Figure 8：Receiver Reference Circuit for AOUT1

2.1.3.2. Headset Reference Circuit

Close to Module

Close to Socket

GND

Module

GND

10pF

33pF

10pF

33pF

10pF

33pF

Differential
layout

GND

4.7uF

MIC2N

33pF

33pF

ESD

MIC2P

GND

68R

GND

LOUDSPKP

3

0R

22uF

33pF

10pF

ESD

4
2
1

Amphenol
9001-8905-050

AGND
GND

AGND

Figure 9：Headset Reference Circuit

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2.1.3.3. SPK Reference Circuit

Close to Speaker
GND
Differential
layout
10pF

Module

ESD

33pF
0R

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LOUDSPKP

10pF

33pF

0R

LOUDSPKN

33pF

10pF

8 ohm

ESD

GND

Figure 10：SPK Reference Circuit

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2.1.4.

M80

2.1.4.1. Microphone Reference Circuit
M80 provides electrets-microphone bias voltage for AIN1 and AIN2. Reference circuit for microphone is
illustrated as following figure.
Close to Microphone

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GND

Differential layout

Module

10pF

33pF

10pF

33pF

ESD

MICxP

Electret
Microphone

MICxN

33pF

10pF

ESD

GND

Figure 11：Microphone Reference Circuit for AIN1&AIN2

2.1.4.2. Receiver Reference Circuit

Close to speaker
GND

Differential layout

10pF

33pF

10pF

33pF

10pF

33pF

ESD

Module

SPK1P

SPK1N
ESD

GND

Figure 12：Receiver Reference Circuit for AOUT1

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Close to speaker
GND

Differential layout
33pF

10pF

Module

SPK2P

ESD

22uF

AGND

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Figure 13：SPK Reference Circuit for AOUT2

Close to speaker
GND

Differential
layout

Module

Amplifier
circuit

10pF

33pF

ESD

10pF

33pF

ESD

C1

SPK2P
AGND

C2

GND

Figure 14：SPK Reference Circuit with audio power amplifier for AOUT2

Note

TPA6205A1 from TEXAS INSTRUMENTS is recommended, which is a audio power amplifier device and
can driver a 8Ω speaker impedance.

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2.1.4.3. Headset Reference Circuit

Close to Socket
Differential
layout

Module

GND

4.7uF

33pF

MIC2N
MIC2P

33pF
ESD

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68R

22uF

SPK2P

3

33pF

10pF

4
2
1

ESD

Amphenol
9001-8905-050

AGND

AGND

GND

Figure 15：Headset Reference Circuit

2.1.4.4. SPK Reference Circuit

Close to speaker
GND

Differential layout

33pF

10pF

Module

ESD

0R

LOUDSPKP

100pF

0R

LOUDSPKN

33pF

10pF

ESD

GND

Figure 16：SPK Reference Circuit

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Notes
1. Capacitors have to place close to audio component or audio interface and layout must be short.
2. Antenna interface must be stay away from audio components and layout of audio circuit. Layout of
power supply must be stay away from audio and cannot be parallel.
3. Differential audios have to meet the rule of layout.

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2.2. Ringtone

M1x does not support ringtone via channel AOUT1, but support to output ringtone via channel AOUT2.
M95 outputs ringtone via channel AOUT2 by default.

M80 outputs ringtone via channel AOUT2 by default; channel AOUT1 can output ringtone via
AT+QAUDCH=0 and AT+QRCH=1. Please refer to AT command description for detailed information
about AT+QRCH.

AT+QRCH

Test Command
AT+QRCH=?

Response
+QRCH: (0,1)
OK

Read Command
AT+QRCH?

Response
+QRCH: 
OK

Write Command
AT+QRCH=

Response
OK

If error is related to ME functionality:
+CME ERROR: 

Reference

Parameter


0
1

Default output channel is AOUT2. (M80’s default audio channel is
AOUT2/AOUT3.
Output ringtone at any audio channel which is decided by AT+QAUDCH. (e.g. if

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AT+QAUDCH=0, ringtone will output via AOUT1)

2.3. Hands-free Application at Channel AIN1/AOUT1
Channel AIN1/AOUT1 could be used as hands-free function, because input audio signal is differential
circuit and it is a good way to suppress common-mode noise.

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SPK circuit is recommended as following:

SPK1N

SPK1P

C308

100nF R308 20K

4

C309

100nF R309 20K

3
1
2

R310

100K

R313

100K

R314

100K

IN-

VO+

IN+

VO-

SHUT_DOWN

VDD

BYPASS

GND

5

FB301

8

FB302

6
7

C19

C20

10uF

33uF

C310

C313

C4

10pF

33pF

C311
10pF

C2
33pF

C312

C3

10pF

33pF

Close to speaker

220nF

VBAT

GPIO_SHUTDOWN

Figure 17：Hands-free Reference Circuit at Channel AIN1/AOUT1

Note

GPIO_SHUTDOWN is controlled by I/O of external chip.

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2.4. Suggestion for Audio Layout
Power supply ripple, unbalanced ground and RF burst radiation have negative effect to audio layout.
Layout of MIC1P/MIC1N, SPK1P/SPK1N must meet the rule of differential signal. Moreover, these two
pairs of signals should be separated from each other by flooding ground to avoid echo issue from SPK
signal to MIC signal. Figure 18 shows an example.

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Figure 18：Layout of Audio

2.5. TDD Noise Solution

It is important to avoid or reduce TDD noise in audio circuit design and layout. This chapter provides
some solution to resolve it.
1.

It is strongly recommended to add an electrets-microphone within two capacitors (10pF and 33pF) in
handset and hands-free application. These two capacitors could largely suppress coupling TDD
noise from RF interference.

2.

Capacitors have to place close to audio component or audio interface, layout must be short.

3.

Flood ground area should be as large as possible to reduce the ground impedance and improve
ground integrality.

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4.

Reduce power voltage ripple, especially the power supply in audio circuits. A wide layout is used from
power source (like adapter interface, battery connector, or LDO output pin) to audio power supply.
Good antenna matching is also important to reduce power ripple.

5.

The filtering capacitors and ESD protection devices should be connected to main digital ground, and
other audio components should use AGND from the module interface. Please be noted that the
AGND pin should not be connected with main digital ground at PCB, or else, it could lead to TDD
noise.

6.

Antenna must be stay away from audio components and layout of audio circuit. Keep the distance at
least 5cm from antenna to microphone.

7.

Layout of power supply must be stay away from audio and cannot be parallel.

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2.6. Suggestion for Mechanical Design

It is important to consider how to suppress echo in the equipment with hands-free function or in an
application which microphone and speaker are very close to each other.
The mechanical structure design has significant impact on echo issue. If it is not properly designed, the
echo suppressing arithmetic in software could not make up echo issue caused by bad mechanical
structure, and even force to redesign.
Echo issue could be generated by several paths as shown in Figure 19.

Figure 19：Five Echo Paths

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In these five paths, internal air-path and direct air-path are the first influential factors. Other three factors
(vibrations through casework, vibrations through PCB, distant echoes) are secondary.
How to deal with echo issue from internal air-path:
Separating microphone from internal space of chassis by foam or rubber ring can effectively suppress the
inner echo interference. Figure 20 shows recommended design for microphone socket.

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Figure 20：Microphone Socket Design

Note

The best installation way of microphone socket is to encase microphone by silicone cover except for front
cavity, and design a cylindrical hole whose center is the exit hole inside the chassis, make the microphone
with silicone cover just fit the cylindrical hole, so as to only let voice enter into microphone from the exit
hole, and not from leak of chassis interior. Certain air space room should be reserved in the front cavity of
microphone as it is necessary for good microphone performance.

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Figure 21 shows recommended design for speaker socket.

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Figure 21：Speaker socket design

A good way to suppress the internal echo path is to seal the rear cavity of receiver, which is usually
expensive. The rear cavity of receiver and speaker is important for good voice quality. A sealed rear cavity
with sufficient space could produce a good voice output. An 8Ω speaker is often big and difficult to give an
independently sealed rear cavity for it. However, sealing microphone socket in chassis is always useful.
Furthermore, the whole chassis must be sealed as far as possible. If there is any unavoidable leak hole,
keep it far away from microphone. If the leak hole is close to microphone, the voice coming from the hole
could be picked up by MIC, and then leads to echo at the far end. If the leak hole is close to speaker, the
output voice quality could be aggravated at certain extent.

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2.7. Component of SPK
A SPK and receiver with higher sensitivity, flatter frequency response, less THD and impedance of
32Ω(receiver), 16Ω(receiver) or 8Ω(speaker) is recommended. These technical data are often shown in
data sheet of SPK and receiver. For SPK, its frequency response and THD performance can be tested by
speaker test system. SPK frequency and THD response are shown in Figure 22 and Figure 23.

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Figure 22：SPK Frequency Response

Note

Horizontal axis is frequency, longitudinal axis is loudness and unit is dB.

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Figure 23：SPK THD

Note
1.
2.

Horizontal axis is frequency, longitudinal axis is distortion and unit is %
Figure 23, the three colors represent three venders’ products. After comprehensive comparison, the
green one performs the best, and the blue one is second, and the red one is the worst.

2.8. Component of Microphone

It is recommended to use an electret microphone with a sensitivity of -42±3dB/Pa @ 2V（not less than
-44±3dB）and impedance of 2.2kΩ . If RF TDD noise is detected at the MIC, please contact MIC vendor
for product with better RF suppression capability. Furthermore, the microphone channel circuit can be
optimized to decrease TDD issue at MIC side.

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3

Description and Suggestion

M1x, M95 has two audio channels in hardware, named AIN1/AOUT1 and AIN2/AOUT2. Three channels
are defined in software, named channel 0, channel 1 and channel 2. Software channel 0 is applied in
hardware channel AIN1/AOUT1, software channel 1 and channel 2 are applied as hardware channel
AIN2/AOUT2. Headset application is used at software channel 1. Software channel 2 is designed for
hands-free application of hardware channel AIN2/AOUT2.

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M80 has three audio channels in hardware, named AIN1/AOUT1, AIN2/AOUT2 and AOUT3. Channel
AOUT3 is used as output of hands-free application. Software channel 0 is applied as hardware channel
AIN1/AOUT1. Software channel 1 is applied as hardware channel AIN1/AOUT1.

3.1. AT Command

Audio parameters will be introduced as following chapter and audio parameters can be set via AT
command.

3.1.1.

AT+QAUDCH

AT+QAUDCH is used to read and set audio software channel. How to read and set audio software
channel via AT+QAUDCH is shown as following:

AT+QAUDCH

Test Command
AT+QAUDCH=?

Response
+QAUDCH: (list of supported s)
OK

Read Command
AT+QAUDCH?

Response
+QAUDCH: 
OK

Write Command
AT+QAUDCH=[]

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Response
OK
If error is related to ME functionality:
+CME ERROR: 

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Reference

Parameter


3.1.2.

0
1
2

Normal audio channel (default)
Headset audio channel
Loudspeaker audio channel

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How to Modify Volume

3.1.2.1. AT+QMIC

AT+QMIC is used to modify the analog gain of microphone. It can increase or reduce the gain of
microphone.

AT+QMIC

a

Test Command
AT+QMIC=?

Response
+QMIC: (list of supported s）, (list of supported
s)
OK

Read Command
AT+QMIC?

Response
+QMIC:
,,
OK

Write Command
AT+QMIC=,

Response
OK
If error is related to ME functionality:
+CME ERROR: 

Reference

Parameter


0
1
2

Normal microphone
Headset microphone
Loudspeaker microphone

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 Range is 0 - 15

3.1.2.2. AT+CLVL
AT+CLVL is used to modify the analog gain of receiver. It can increase or reduce loudness of downlink
speech.

AT+CLVL

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Test Command
AT+CLVL=?

Response
+CLVL: (list of supported s)
OK

Read Command
AT+CLVL?

Response
+CLVL: 
OK

Write Command
AT+CLVL=

Reference
GSM 07.07

Parameter


Note

Response
OK
If error is related to ME functionality:
+CME ERROR: 

Integer type value (0-100) with manufacturer specific range (Smallest value represents
the lowest sound level)

If the gain-level is too high, receiving distortion would happen.

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3.1.2.3. AT+QSIDET
AT+QSIDET is used to adjust the side tone gain.

AT+QSIDET
Test Command
AT+QSIDET=?

Response
+QSIDET: (list of supported s)
OK

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Read Command
AT+QSIDET?

Response
+QSIDET(NORMAL_AUDIO): 

OK
+QSIDET(HEADSET_AUDIO): 
OK

Write Command
AT+QSIDET=

Reference
GSM 07.07

Response
OK
If error is related to ME functionality:
+CME ERROR: 

Parameters:


Note

Gain level of side tone.
Value range: 0~255
Disable: 0

Side tone is disabled and cannot be adjusted in hands-free application.

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3.1.3.

Echo Algorithm

AT+QAPS is used to modify echo algorithm parameters of all three software audio channels.

AT+QAPS
Set Command
AT+QAPS=,,
,

Response
+QAPS: ,[,[,]][,]
OK

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Set Command
AT+QAPS=,[,[,<
para3>]][,]

Response
If  is read,
+QAPS:

OK

If  is write,
OK
If format is error, response
+CME ERROR: 

Parameters：








Operation
0 Get old value
1 Set new value
Type of parameters
0 Input FIR Coeffs
1 Output FIR Coeffs
2 FIR output Index
3 Speech Common Para
4 Speech Mode Para
Group/mode of parameters
When para1=0/1/4, para2 is a must.
Ranges from 0~2, corresponding to the audio mode.
0 Normal mode
1 Headset mode
2 Loudspeaker mode
See detailed information in notes below.
Batch number of parameters.

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When para1=0/1, para3 is a must and 10 elements consist one batch.
List of integers, with dot (“.”) separated.

Note

Par0：
（AEC）Acoustic echo control NLP control word
Par1：
（AEC）AEC control word
Par2：
（AEC）Echo suppressor control word
Par3：NDC
Par4：NDC
Par5：NDC
Par6：NDC
Par7：DGA Digital gain control word
Par8：NDC
Par8：NDC
Par9：NDC
Par10：NDC
Par11：NDC
Par12：AES Aggressive echo suppression
Par13：DMNR
Par14：DMNR
Par15：N/A

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For example:

Read:
AT+QAPS=0,4,0 // Read audio parameters of normal audio mode (software channel 0).
+QAPS: 4,0,"96.253.16388.31.57351.31.400.0.80.4325.99.0.20488.0.0.8192"
OK

AT+QAPS=0,4,1 // Read audio parameters of headset audio mode (software channel 1).
+QAPS: 4,1,"96.253.10756.31.57351.31.400.0.80.4325.99.0.16392.0.0.0"
OK

AT+QAPS=0,4,2
// Read audio parameters of loudspeaker audio mode (software channel 2).
+QAPS: 4,2,"254.224.3208.31.57351.24607.400.132.80.4325.99.0.16392.0.0.0"
OK
Write and Save:
//Write and save audio parameters of normal audio mode (software channel 0).

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AT+QAPS=1,4,0, "96.253.16388.31.57351.31.400.0.80.4325.99.0.20488.0.0.8192"
OK
//Write and save audio parameters of loudspeaker audio mode (software channel 2).
AT+QAPS=1,4,2, "254.224.3208.31.57351.24607.400.132.80.4325.99.0.16392.0.0.0"
OK

Note

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Quectel module has configured default parameters in software. For some special applications, such as
AIN1/AOUT1 being applied in hands-free, or echo issue caused by bad circuits or mechanical structure.
Some of parameters can be modified to fix echo issue. Advices of audio parameters in different
application are provided in the next section.

3.1.3.1. Description of Par0, Par2 and Par12






Par0-（AEC） NLP control word
Value range: 0~256
Disable: 0
The large value has a positive effect on ECHO issue.
Par2-（AEC）Echo suppressor control word
Value range: 32512~0
Disable: 32512
The smaller value has a positive effect on ECHO issue.
Par12- AES Aggressive echo suppression
Value range: 32513~0
Disable: 32513
The smaller value has a positive effect on ECHO issue.

\ Note

Par0, Par2, Par12 have the most significant effect on ECHO issue.

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3.1.3.2. Recommended Application Field
There are some recommended parameters when module works in voice or DTMF application, shown as
below:
Voice
AT+QAPS=1,4,0,"96.253.10756.31.57351.31.400.0.80.4325.99.0.20488.0.0.8192"
AT+QAPS=1,4,0,"128.253.10756.31.57351.31.400.0.80.4325.99.0.16392.0.0.8192"
AT+QAPS=1,4,0,"192.253.10756.31.57351.31.400.0.80.4325.99.0.16392.0.0.8192"
AT+QAPS=1,4,0,"192.253.10756.31.57351.31.400.0.80.4325.99.0.8223.0.0.8192"
AT+QAPS=1,4,0,"192.253.5256.31.57351.31.400.0.80.4325.99.0.8223.0.0.8192"
AT+QAPS=1,4,0,"192.253.2218.31.57351.31.400.0.80.4325.99.0.8223.0.0.8192"
AT+QAPS=1,4,0,"248.253.2218.31.57351.31.400.0.80.4325.99.0.8223.0.0.8192"

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DTMF
AT+QAPS=1,4,2,"128.224.2218.31.57351.24607.400.132.80.4325.99.0.8223.0.0.0"
AT+QAPS=1,4,2,"192.224.750.31.57351.24607.400.132.80.4325.99.0.2079.0.0.0"
AT+QAPS=1,4,2,"224.224.511.31.57351.24607.400.132.80.4325.99.0.513.0.0.0"
AT+QAPS=1,4,2,"128.253.2218.31.57351.24607.400.132.80.4325.99.0.8223.0.0.0"
AT+QAPS=1,4,2,"192.253.750.31.57351.24607.400.132.80.4325.99.0.2079.0.0.0"
AT+QAPS=1,4,2,"224.253.511.31.57351.24607.400.132.80.4325.99.0.513.0.0.0"

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4

Appendix A

Table 2： Reference Document
NO.
[1]
[2]

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Name

Remark

M1x_AT_Commands_Manual

AT Commands Manual

Mxx_Hardware_Design

Hardware Design

Table 3： Description of ECHO and TDD noise
Noun

ECHO

TDD noise

Explanation

Talking quality can be obviously affected when echo problem is present.
Description of ECHO issue: The far end could hear its own voice from the
module side (the near end) in talking.
ECHO issue can be caused by the near end of some reasons, such as
receiving circuit coupling to the microphone circuit, unsealed mechanical
structure, high SPK loud voice, or high sensitivity microphone. ECHO issue
has a negative effect on talking.
TDD noise could be present at the far end of the near end while talking. RF
power aptitude generates a burst keeping 576us in every 4.615ms. It could
be coupling to audio circuit. The envelope curve of the RF burst could be
present due to filtering effect and make a noise in the audio circuit path as a
constant pulse at 217Hz and its harmonic frequencies. Another of the reason
is from the power supply. The burst consumption of current can cause
obvious ripple at the supply voltage at 217Hz. If the ripple at the supply
voltage conducts to audio circuit through power supply or ground, TDD noise
could be present at the far end or the near end.

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