Neoway N11 Series Installation manual

N11
Hardware User Guide
Issue 1.4
Date 2019-07-09
Neoway Product Document

N11
Hardware User Guide
Copyright © Neoway Technology Co., Ltd
i
Copyright © Neoway Technology Co., Ltd 2018. All rights reserved.
No part of this document may be reproduced or transmitted in any form or by any means without prior written
consent of Neoway Technology Co., Ltd.
is the trademark of Neoway Technology Co., Ltd.
All other trademarks and trade names mentioned in this document are the property of their respective
holders.
Notice
This document provides guide for users to use N11.
This document is intended for system engineers (SEs), development engineers, and test engineers.
THIS GUIDE PROVIDES INSTRUCTIONS FOR CUSTOMERS TO DESIGN THEIR APPLICATIONS.
PLEASE FOLLOW THE RULES AND PARAMETERS IN THIS GUIDE TO DESIGN AND COMMISSION.
NEOWAY WILL NOT TAKE ANY RESPONSIBILITY OF BODILY HURT OR ASSET LOSS CAUSED BY
IMPROPER OPERATIONS.
THE INFORMATION IN THIS DOCUMENT IS SUBJECT TO CHANGE WITHOUT NOTICE DUE TO
PRODUCT VERSION UPDATE OR OTHER REASONS.
EVERY EFFORT HAS BEEN MADE IN PREPARATION OF THIS DOCUMENT TO ENSURE ACCURACY
OF THE CONTENTS, BUT ALL STATEMENTS, INFORMATION, AND RECOMMENDATIONS IN THIS
DOCUMENT DO NOT CONSTITUTE A WARRANTY OF ANY KIND, EXPRESS OR IMPLIED.
Neoway provides customers complete technical support. If you have any question, please contact your
account manager or email to the following email addresses:
[email protected]
[email protected]
Website: http://www.neoway.com

N11
Hardware User Guide
Copyright © Neoway Technology Co., Ltd
ii
Contents
1 About N11 ..................................................................................................2
1.1 Overview ...................................................................................................................................... 2
1.2 Block Diagram.............................................................................................................................. 2
1.3 Specifications ............................................................................................................................... 3
2 Pin Description ..........................................................................................5
2.1 Pin Allocation................................................................................................................................ 5
2.2 Pin Definition ................................................................................................................................ 6
3 Application Interfaces ................................................................................8
3.1 Power Supply ............................................................................................................................... 8
3.1.2 VBAT.................................................................................................................................... 8
3.1.3 VDDIO_2P8....................................................................................................................... 12
3.1.4 On/Off Control and Procedure........................................................................................... 12
3.2 UART.......................................................................................................................................... 15
3.3 DTR and RING........................................................................................................................... 19
3.3.2 DTR Pin ............................................................................................................................. 19
3.3.3 RING Signal....................................................................................................................... 21
3.4 SIM Card .................................................................................................................................... 22
3.5 LIGHT......................................................................................................................................... 23
3.6 RF Interface................................................................................................................................ 24
3.6.1 RF Design and PCB Layout .............................................................................................. 24
3.6.2 Antenna Assembling.......................................................................................................... 26
4 Electric Features and Reliability ..............................................................28
4.1 Electric Feature .......................................................................................................................... 28
4.2 Temperature ............................................................................................................................... 28
4.3 Current ....................................................................................................................................... 29
4.4 ESD Protection........................................................................................................................... 30
5 RF Features.............................................................................................31
5.1 Operating Band .......................................................................................................................... 31
5.2 Transmitting Power and Receiving Sensitivity ........................................................................... 31
5.2.1 Transmitting Power............................................................................................................ 31
5.2.2 Receiving Sensitivity.......................................................................................................... 33
6 Mechanical Features ...............................................................................34
6.1 Dimensions................................................................................................................................. 34
6.2 Label........................................................................................................................................... 35
6.3 Package ..................................................................................................................................... 35
6.3.1 Tape & Reel Packaging ..................................................................................................... 36
6.3.2 Humidity-Sensitive............................................................................................................. 37
6.4 Storage....................................................................................................................................... 37
7 Mounting N11 onto Application Board......................................................38

N11
Hardware User Guide
Copyright © Neoway Technology Co., Ltd
iii
7.1 Bottom Dimensions .................................................................................................................... 38
7.2 Application Foot Print ................................................................................................................. 39
7.3 Stencil......................................................................................................................................... 39
7.4 Solder Paste............................................................................................................................... 39
7.5 SMT Profile................................................................................................................................. 40
8 Safety Recommendations .......................................................................42
9 Abbreviations ...........................................................................................43

N11
Hardware User Guide
Copyright © Neoway Technology Co., Ltd
iv
Table of Figures
Figure 1-1 N11 Block Diagram ........................................................................................................... 3
Figure 2-1 Top view of N11 module.................................................................................................... 5
Figure 3-1 Recommended design 1................................................................................................... 9
Figure 3-2 Recommended design 2................................................................................................... 9
Figure 3-3 Recommended design 3................................................................................................. 10
Figure 3-4 Recommended design 4..................................................................................................11
Figure 3-5 Power-on timing.............................................................................................................. 13
Figure 3-6 Power-off procedure ....................................................................................................... 13
Figure 3-7 Reference circuit for power-on/off control....................................................................... 14
Figure 3-8 Reference circuit for power-on/off controlled by high level............................................. 14
Figure 3-9 Signal connection between DCE and DTE..................................................................... 15
Figure 3-10 Level shifting circuit 1 ................................................................................................... 16
Figure 3-11 Level shifting circuit 1.................................................................................................... 17
Figure 3-12 Recommended level shifting circuit 2........................................................................... 18
Figure 3-13 Process of entering sleep mode ................................................................................... 19
Figure 3-14 Incoming call service process....................................................................................... 20
Figure 3-15 Outgoing call service process....................................................................................... 20
Figure 3-16 Process of exiting from sleep mode ............................................................................. 21
Figure 3-17 RING indicator for incoming call ................................................................................... 21
Figure 3-18 RING indicator for SMS ................................................................................................ 22
Figure 3-19 Reference design of SIM card interface ....................................................................... 22
Figure 3-20 LED indicator ................................................................................................................ 23
Figure 3-21 L network ...................................................................................................................... 24
Figure 3-22 T network ...................................................................................................................... 24
Figure 3-23 Pi network ..................................................................................................................... 25
Figure 3-24 RF layout reference ...................................................................................................... 26
Figure 3-25 Specifications of MM9329-2700RA1 ............................................................................ 26

N11
Hardware User Guide
Copyright © Neoway Technology Co., Ltd
v
Figure 3-26 RF connections............................................................................................................. 27
Figure 6-1 N11 dimensions (Unit: mm) ............................................................................................ 34
Figure 6-2 N11 label......................................................................................................................... 35
Figure 6-3 N11 V2 label.................................................................................................................... 35
Figure 7-1 N11 bottom dimensions (Unit: mm) ................................................................................ 38
Figure 7-2 Recommended PCB foot print (Unit: mm)...................................................................... 39
Figure 7-3 SMT furnace temperature curve..................................................................................... 40

N11
Hardware User Guide
Copyright © Neoway Technology Co., Ltd
vi
Table of Tables
Table 1-1 N11 Specifications.............................................................................................................. 3
Table 2-1 N11 Pin definition ............................................................................................................... 6
Table 3-1 Power supply and switch interface..................................................................................... 8
Table 3-2 UART................................................................................................................................ 15
Table 3-3 DTR and RING pins ......................................................................................................... 19
Table 3-4 SIM card interfaces .......................................................................................................... 22
Table 3-5 LED indicator.................................................................................................................... 23
Table 4-1 Electric feature of the module .......................................................................................... 28
Table 4-2 Temperature Feature........................................................................................................ 28
Table 4-3 Current feature ................................................................................................................. 29
Table 4-4 ESD feature of the module............................................................................................... 30
Table 5-1 Operating band................................................................................................................. 31
Table 5-2 Transmitting power (GSM850&EGSM900) ...................................................................... 31
Table 5-3 Transmitting power (DCS1800&PCS1900) ...................................................................... 32

N11
Hardware User Guide
Copyright © Neoway Technology Co., Ltd
vii
About This Document
Scope
This document is applicable to N11 series.
It defines the features, indicators, and test standards of the N11 module and provides reference for
the hardware design of each interface.
Audience
This document is intended for system engineers (SEs), development engineers, and test engineers.
Change History
Issue
Date
Change
Changed By
1.0
2018-03
Initial draft
Wang Qiang
1.1
2018-03
Modified the signal
Zhuo JianZheng
1.2
2018-09
Added N11 V2
Zhuo JianZheng
1.3
2018-11
⚫Corrected SIM design
⚫Added guidelines to reference designs
⚫Added antenna matching
Zhuo JianZheng
1.4
2019-06
Modified supply voltage
Gong Hualiang
Conventions
Symbol
Indication
This warning symbol means danger. You are in a situation that could cause fatal
device damage or even bodily damage.

N11
Hardware User Guide
Copyright © Neoway Technology Co., Ltd
viii
Means reader be careful. In this situation, you might perform an action that
could result in module or product damages.
Means note or tips for readers to use the module
Related Documents
Neoway_N11_Datasheet
Neoway_N11_Product_Specifications
Neoway_N11_AT_Command_Mannual
Neoway_N11_EVK_User_Guide

N11
Hardware User Guide
Copyright © Neoway Technology Co., Ltd
2
1 About N11
N11 is a compact wireless GSM/GPRS module. It provides high-quality SMS and data services. N11
is widely used in industrial and consumer applications.
N11 series include two variants: N11 and N11 V2. These two variants are completely compatible with
each other in pin definition, packaging, and electric features. In this document, N11 refers to both
variants if not specified.
1.1 Overview
The N11 module adopts 20-pin LGA package and its dimensions are 15.8 mm x 13.8 mm x 2.5 mm,
which can meet most customer requirements for space reduction. It has the following hardware
resources and features:
⚫UART interface, used for data communications, software upgrades and debugging
⚫Support SIM card 1.8/3.0V self-adaption
⚫Support RING (incoming call and SMS reminder)/NET_LIGHT (network indicator)/DTR (sleep
mode) function
1.2 Block Diagram
The N11 module consists of baseband controller, Flash ROM, RF section, application interfaces, etc.
All sections coordinate with each other to provide such communication functions as GPRS data. Its
design block diagram is shown in Figure 1-1.

N11
Hardware User Guide
Copyright © Neoway Technology Co., Ltd
3
Figure 1-1 N11 Block Diagram
ON/OFF
Power
Manager
Flash Analog
Baseband Digital Baseband
RF Front-end-module 26MHz
Crystal
Digital
Iterface
SIM UART
SIM
VBAT
RF transceiver
1.3 Specifications
Table 1-1 N11 Specifications
Specifications
Description
Dimensions
(15.8±0.1) mm x (13.8±0.1) mm x (2.5±0.2) mm (H x W x D)
Weight
1.3 g
Package
20-pin LGA
Operating Temperature
-40 ºC to +85 ºC
Operating Voltage
3.4 V to 4.3 V (3.9 V is recommended)
Peak Current
Max 2.0 A
Operating Current (Idle)
11 mA
Current in Sleep Mode
⚫< 2.5 mA (on live network)

N11
Hardware User Guide
Copyright © Neoway Technology Co., Ltd
4
⚫< 1.1 mA (through instrument, DRX=9)
Frequency band
GSM850/EGSM900/DCS1800/PCS1900
Sensitivity
< -108 dBm
Transmit power
⚫GSM850/EGSM900 Class4(2W)
⚫DCS1800/PCS1900 Class1(1W)
Protocol
Support GSM/GPRS Phase2/2+
AT commands
⚫GSM07.07
⚫Extended AT commands
SMS
⚫Support PDU and TEXT mode
⚫Support SMS message receiving and sending and alert for new
SMS messages
⚫Support SMS message management: reading/deleting/storage/list
GPRS Features
⚫Support GPRS CLASS 12
⚫Theoretical maximum uplink transmission rate: 85.6 Kbit/s
⚫Theoretical maximum downlink transmission rate: 85.6 Kbit/s
⚫Embedded TCP/IP protocol, support multi-link
⚫Support server and client mode
UART
⚫Support AT command sending, data transmission and firmware
download
⚫Support baud rate from 9600 bit/s to 115200 bit/s
Antenna Feature
50 Ω characteristic impedance

N11
Hardware User Guide
Copyright © Neoway Technology Co., Ltd
5
2 Pin Description
There are 20 pins on N11 and their pads are introduced in LGA package. This chapter describes its
pin definition and features.
2.1 Pin Allocation
Figure 2-1 Top view of N11 module
GND
GND
GND
VBAT
VBAT
ON/OFF
SIM_DATA
SIM_CLK
SIM_RESET
VSIM
UART_RXD
UART_TXD
DEBUG_RXD
DEBUG_TXD
VDDIO_2P8
DTR
NET_LIGHT
RING
GND
ANT
1
2
3
4
5
6
7
8
9
10
20
19
18
17
16
15
14
13
12
11
N11
Top View
POWER GND ON/OFF SIM ANT OTHERS UART

N11
Hardware User Guide
Copyright © Neoway Technology Co., Ltd
6
2.2 Pin Definition
P: indicates power supply pins
NC: indicates pins that are not supported and must not be connected
DI: indicates digital signal input pins
DO: indicates digital signal output pins
AI: indicates analog signal input pins
AO: indicates analog signal output pins
Table 2-1 N11 Pin definition
Pin
Pin Name
I/O
Function
Electrical Level
Characteristics (V)
Remarks
Power supply and Switch Interfaces
2, 3
VBAT
P
Power supply
input
3.4 V to 4.3 V (3.9
V is
recommended)
1, 4,
10,
19
GND
P
Ground
5
ON/OFF
DI
ON/OFF input
0<VIL<0.6;
2.1<VIH<VBAT
Low-level pulse
triggers ON/OFF
state.
15
VDDIO_2P8
P
2.8V power
supply output
Used only for level
shifting and to
supply power for
IO. Load capacity
< 50 mA
UART Interface
12
UART_TXD
DO
UART data
transmit
0<VIL<0.6;
2.1<VIH<3.1;
0<VOL<0.42;
2.38<VOH<2.8
Used for
command sending
and receiving
11
UART_RXD
DI
UART data
receive
SIM Card
6
SIM_DATA
DI/O
SIM card data
0<VIL<0.25*VSIM;
0.75*VSIM<VIH<VSIM;
Compatible with
1.8/3.0 V SIM card
7
SIM_CLK
DO
SIM card clock

N11
Hardware User Guide
Copyright © Neoway Technology Co., Ltd
7
8
SIM_RESET
DO
SIM card reset
0<VOL<0.15*VSIM;
0.85*VSIM<VOH<VSIM
9
VSIM
P
SIM card
power output
Network indicator
17
NET_LIGHT
DO
Network status
LED
2.8 V/4 mA output
Used with AT
commands
SMS and Call Reminder
18
RING
DO
Ring output
0<VIL<0.6;
2.1<VIH<3.1;
0<VOL<0.42;
2.38<VOH<2.8
Detect incoming
voice calls or SMS
messages
Sleep Mode Control
16
DTR
DI
Sleep mode
control
0<VIL<0.6;
2.1<VIH<3.1;
0<VOL<0.42;
2.38<VOH<2.8
Used together with
AT commands
GPRS Antenna
20
ANT
AI/O
GPRS antenna
interface
50 Ωimpedance
Reserved Pins
13
DEBUG_TXD
DO
Reserve a test
point. Do not
connect these pins
to power supply or
ground.
14
DEBUG_RXD
DI
Reserve a test
point. Do not
connect these pins
to power supply or
ground.
The maximum input voltage at all IO ports (including peak signal current) cannot exceed 3.1 V
because the module uses a 2.8 V IO power system. In the application of the module, the IO output
voltage from the 3.3 V power supply system of the external circuit might greatly overshoot 3.1 V due to
the signal integrity design. In this situation, the IO pins of the module might be damaged if the IO signals
are connected to the IO port on the 2.8 V systems. To rectify this issue, take measures to match the
level. For details, see the 3.2 UART.

N11
Hardware User Guide
Copyright © Neoway Technology Co., Ltd
8
3 Application Interfaces
N11 provides power supply and control, communications, RF, and other interfaces to meet customers
requirements in different application scenarios.
This chapter describes how to design each interface and provides reference designs and guidelines.
3.1 Power Supply
Schematic design and PCB layout of power supply are the most critical process in application design
and determine the performance of customers' applications. Please read the design guidelines of
power supply and comply with the correct design principles to obtain the optimal circuit performance.
Table 3-1 Power supply and switch interface
Pin
Signal
I/O
Function
Remarks
2, 3, 4
VBAT
P
Main power supply input
3.4 V to 4.3 V (3.9 V is recommended)
1, 4, 10, 19
GND
P
Ground
5
ON/OFF
DI
ON/OFF input
Low-level triggers ON/OFF state.
3.1.2 VBAT
The power supply design consists of two parts: schematic design and PCB layout.
Schematic Design
Design the circuit of the power supply for N11 based on the input voltage you choose. Generally
there are three types of input voltages:
⚫3.4 V to 4.3 V (3.9 V typically, output by cellphone battery)
⚫4.3 V to 5.5 V (5.0 V typically, output by computer through USB)
⚫5.5 V to 24 V (12 V typically, output by automotive battery)
Figure 3-1 shows schematic design recommended for 3.4 V to 4.3 V input.

N11
Hardware User Guide
Copyright © Neoway Technology Co., Ltd
9
Figure 3-1 Recommended design 1
Power Supply N11 Module
D1 C1 C2 C3 C4
Close to the pin of the module
VBAT
Test point
I_max
C5
⚫The maximum input voltage for the module is 4.3 V and the typical value is 3.9 V.
⚫SMF5.0AG (Vrwm=5V&Pppm=200W) is recommended at D1. The protection voltage across D1
should not exceed the maximum input voltage the module can bear.
Place TVS close to the input interface of the power supply to clamp the surge voltage before it
enters back-end circuits. Therefore, the back-end components and the module are protected.
⚫A large bypass tantalum capacitor (220 μF or 100 μF) or aluminum capacitor (470 μF or 1000
μF) is expected at C1 to reduce voltage drops during bursts. Its maximum safe operating voltage
should be larger than 1.5 times the voltage across the power supply.
⚫Place low-ESR bypass capacitors close to the module to filter out high-frequency noise from the
power supply.
A controllable power supply is preferable if the module is used in harsh conditions. Figure 3-2 shows
the recommended schematic design.
Figure 3-2 Recommended design 2
S
G
D
R4
100 kΩ
C4
10 μF
Q2
Q1
TVS2
5V C3
470 μFC5
0.1 μFC6 100pF C7
33 pF
R1
2 kΩ
R2
10 kΩ
C1
10 μFC2 0.1 μF
BC
E
VIN (3.8V) VBAT
PWR_EN

N11
Hardware User Guide
Copyright © Neoway Technology Co., Ltd
10
⚫Select an enhanced p-MOSFET at Q1, of which the maximum safe operating voltage and drain
current is high and Rds is low.
⚫Select a common NPN bipolar transistor or a digital NPN bipolar transistor at Q2. If selecting
common NPN bipolar transistor, reserve enough tolerances of resistors at R1 and R2 in design,
especially for the situation in which operating voltage of the bipolar transistor might increase in
low temperature.
⚫Place TVS2 close to the input interface of the power supply to clamp the surge voltage before it
enters back-end circuits. Therefore, the back-end components and the module are protected.
⚫Place C3 close to the module. A large bypass tantalum capacitor (220 μF or 100 μF) or
aluminum capacitor (470 μF or 1000 μF) is expected at C1 to reduce voltage drops during
bursts. Its maximum safe operating voltage should be larger than 1.5 times the voltage across
the power supply.
⚫Place low-ESR bypass capacitors close to the module to filter out high-frequency noise from the
power supply.
The following design is recommended for 4.3 V to 5.5 V input.
Figure 3-3 Recommended design 3
U1
C1
100 μF
TAN
R1
100 kΩ
C2
0.1 μF
R2
47.5 kΩ
C3
470 μF
TAN
C5
0.1 μF
TVS2
5V
EN
VIN
VOUT
ADJ C4
10 μFC6 100 pF C6
33 pF
GND
GND
PWR_EN
VIN (5V)
VBAT
⚫Design with LDO is more simple and efficient when the output of power supply is close to the
permissible voltage across VBAT.
⚫Select an LDO that can output a current larger than 2 A at U1 to ensure the performance of the
module. MIC29302WU is recommended.
⚫Place TVS2 close to the input interface of the power supply to clamp the surge voltage before it
enters back-end circuits. Therefore, the back-end components and the module are protected.
⚫Place C3 close to the module. A large bypass tantalum capacitor (220 μF or 100 μF) or
aluminum capacitor (470 μF or 1000 μF) is expected to reduce voltage drops during bursts. Its
maximum safe operating voltage should be larger than 1.5 times the voltage across the power
supply.

N11
Hardware User Guide
Copyright © Neoway Technology Co., Ltd
11
⚫Place low-ESR bypass capacitors close to the module to filter out high-frequency noise from the
power supply.
The following design is recommended for 5.5 V to 24 V input.
Figure 3-4 Recommended design 4
VIN
EN
RT/CLK
P-PAD
GND
BOOST
SW
FB
COMP
R1
47.5KΩ
12KΩ
100pF 0.01uF
L1
3.3uH
0.1uF
VBAT
470uF 100uF 22uF 0.1uF 100pF 33pF 1kΩ
47.5kΩ
12kΩ
SS36
VIN
(4.5V-42V)
C1
100uF C2 22uF C3 0.1uF
TPS54340
D1
C4 C5
C6
C7 C8 C9 C10 C11C12
R2
R3
R4
R5
PWR_EN
⚫Select DC-DC that outputs a maximum current larger than 2 A when the output of power supply
is much larger than the permissible voltage across VBAT.
⚫500 kHz or higher switching frequency is recommended for DC-DC.
⚫The switching frequency of DC-DC might produce EMC noise and it determines the performance
of end products.
⚫Add surge protection to the front end of the power supply circuit if automotive battery supplies
power. The maximum safe operating voltage of the component should be larger than 42 V.
⚫Place TVS2 close to the input interface of the power supply to clamp the surge voltage before it
enters back-end circuits. Therefore, the back-end components and the module are protected.
⚫Place C7 close to the module. A large bypass tantalum capacitor (220 μF or 100 μF) or
aluminum capacitor (470 μF or 1000 μF) is expected to reduce voltage drops during bursts. Its
maximum safe operating voltage should be larger than 1.5 times the voltage across the power
supply.
⚫Place low-ESR bypass capacitors close to the module to filter out high-frequency noise from the
power supply.
PCB Layout Guidelines
⚫TVS diodes dissipate the transient pulse power during a surge and have a short response time.
Place the TVS as close to the interface as possible to ensure that the surge voltage can be
clamped before the pulse is coupled to the neighbor traces.
⚫Place filer capacitors close to the power pin of the module to filter out the high-frequency noise
from the power supply.

N11
Hardware User Guide
Copyright © Neoway Technology Co., Ltd
12
⚫Ensure that the width of PCB traces for VBAT circuits allows 2 A current and ensure no obvious
decrease of loop voltages. Trace width of VBAT should be at least 2 mm and the ground plane
should be as complete as possible. The traces of power supply circuit should be as short and
wide as possible.
⚫Noise-sensitive circuits such as audio and RF, should be placed far away from power supply
circuits, especially when the DC-DC is adopted in the design.
⚫Ensure that the loop is minimum in design with DC-DC since the frequency is high at SW pin.
Place sensitive components far away from SW pin in case of noise coupling. Place feeding
components as close to FB pin and COMP pin as possible.
⚫Connect GND pins and bottom pads to ground to optimize heat sink and separate noise.
In GSM/GPRS mode, RF data is transmitted in burst mode that generates voltage drops on power
supply. Furthermore, this results in a 216 Hz noise through power and the transient peak current is up to
2A. Ensure low resistance of power supply trace in design to avoid voltage drop.
Never use a diode to make the drop voltage between a higher input and module power. Otherwise,
Neoway will not provide warranty for product issues caused by this. In this situation, the diode will
obviously decrease the module performances, or result in unexpected restarts, due to the forward
voltage of diode will vary greatly in different temperature and current. The module might not work
properly with a diode power supply.
3.1.3 VDDIO_2P8
N11 provides one VDDIO_2P8 pin that outputs 2.8 V@50 mA.
It is recommended that VDDIO_2P8 is used only for level shifting and IO power supply.
3.1.4 On/Off Control and Procedure
Prior to turning on the module, power on the host MCU and finish the UART initialization. Otherwise
conflictions may occur during initialization, due to unstable conditions. ON/OFF is a pin triggered by
low level pulse and used to turn on or off the module.
Power-On Procedure
While the module is off, pull the ON/OFF pin to ground for at least 1.2 second and then release it,
the module will start.
If the module uses a fixed baudrate, UART port prints an unsolicited message
(\r\nMODEM:STARTUP\r\n), indicating that the module is initialized and the UART is ready to respond
to AT commands.