Jinan USR IOT Technology USR-WIFI232-A2 User manual

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USR-WIFI232-A2
Embedded WiFi Module User Manual
Version：V6.0
Note: this article is based on the firmware version for V5.01.01 and above version of the module,
if the version is lower than this version, some function is not supported.

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Table Of Contents
1 Quick Start.................................................................................................................................................... 6
1.1 Hardware connect............................................................................................................................ 6
1.2 Network connection......................................................................................................................... 7
1.3 communication test.......................................................................................................................... 8
2 Product Overview........................................................................................................................................ 9
2.1 General Description......................................................................................................................... 9
2.2 Device Features............................................................................................................................... 9
2.3 Device Paremeters........................................................................................................................ 10
2.4 Key Application............................................................................................................................... 11
2.5 Package Information......................................................................................................................11
2.5.1 Recommended Reflow Profile.......................................................................................... 11
2.5.2 Device Handling Instruction (Module IC SMT Preparation).........................................11
3 Hardware Introduction.............................................................................................................................. 12
3.1 Pins Definition.................................................................................................................................12
3.1.1 USR-WIFI232-A2 Pins Definition.....................................................................................12
3.2 Mechanical Size............................................................................................................................. 13
3.2.1 USR-WIFI232-A2................................................................................................................13
3.3 Antenna............................................................................................................................................14
3.3.1 External Antenna................................................................................................................ 14
3.4 Evaluation Kit..................................................................................................................................14
3.5 Hardware Reference Design........................................................................................................16
3.5.1 Hardware Typical Application........................................................................................... 16
3.5.2 10/100M Ethernet Interface.............................................................................................. 17
3.5.2.1 Ethernet Connection with Transformer................................................................17
3.5.2.2 Ethernet Connection without Transformer.......................................................... 17
3.5.3 UART Interface....................................................................................................................18
3.5.4 Power Interface...................................................................................................................19
4 Modules Function Description.................................................................................................................19
4.1 User configuration process...........................................................................................................19
4.2 Working mode.................................................................................................................................20
4.2.1 Transparent Mode.............................................................................................................. 20
4.2.2 Serial command mode.......................................................................................................21
4.2.3 GPIO mode..........................................................................................................................22
4.2.4 HTTPD Client mode........................................................................................................... 22
4.3 Wireless Networking......................................................................................................................23
4.3.1 STA........................................................................................................................................24
4.3.2 AP..........................................................................................................................................24
4.3.3 AP+STA................................................................................................................................ 25
4.4 Ethernet Interface Communication............................................................................................. 26
4.4.1 USR-WIFI232-A2 Ethernet Interface Networking (As AP).......................................... 26
4.4.2 USR-WIFI232-A2 Ethernet Interface Networking (As STA, N-Ver)........................... 27
4.4.3 USR-WIFI232-A2 Ethernet Interface Networking (As STA, Z-Ver)............................27
4.5 WI-FI parameter setting................................................................................................................ 28

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4.5.1 Auto- Frequency Function.................................................................................................28
4.5.2 Security.................................................................................................................................28
4.5.3 Search Function for STA................................................................................................... 28
4.5.4 Address Binding..................................................................................................................28
4.6 UART Frame Scheme................................................................................................................... 29
4.6.1 UART Free-Frame..............................................................................................................29
4.6.2 UART Auto-Frame.............................................................................................................. 29
4.7 Network Setting.............................................................................................................................. 30
4.7.1 Socket A............................................................................................................................... 30
4.7.2 Socket B............................................................................................................................... 30
4.8 New function................................................................................................................................... 31
TCP password authentication.....................................................................................................31
4.8.1 Registered Package ID/MAC............................................................................................31
4.8.2 Self-adaption Baudrate......................................................................................................31
4.8.3 WEB IO.................................................................................................................................32
4.8.4 Keepalive............................................................................................................................. 32
4.8.5 Multiple STA parameters................................................................................................... 32
4.8.6 Websocket........................................................................................................................... 32
4.8.7 Fast access Wi-Fi(usr-link)............................................................................................... 33
4.9 Palmodic Signal..............................................................................................................................34
4.10 Parameters Configuration.......................................................................................................... 35
4.11 Firmware Upgrade....................................................................................................................... 35
Web Accessing and AT command set....................................................................................................... 36
4.12 Configuration via Web Accessing............................................................................................. 36
4.12.1 Open Web Management Interface................................................................................ 36
4.12.2 Quick Configure................................................................................................................37
4.12.3 Mode Selection Page.......................................................................................................37
4.12.4 AP Interface Setting Page...............................................................................................38
4.12.5 STA Interface Setting Page.............................................................................................38
4.12.6 Application Setting Page................................................................................................. 39
4.12.7 Ethernet Setting................................................................................................................40
4.12.8 HTTPD Client Mode.........................................................................................................41
4.12.9 WEB IO.............................................................................................................................. 41
4.12.10 Advanced Page.............................................................................................................. 42
4.12.11 Device Management Page........................................................................................... 42
4.13 AT command Introduction...........................................................................................................43
4.13.1 Configuration Mode..........................................................................................................43
4.13.1.1 Switch to Configuration Mode.............................................................................44
4.13.2 AT+ Instruction Set Overview......................................................................................... 44
4.13.2.1 Instruction Syntax Format................................................................................... 46
4.13.2.2 AT+ command Set................................................................................................ 47
4.13.2.2.1 AT+E............................................................................................................ 49
4.13.2.2.2 AT+ENTM....................................................................................................49
4.13.2.2.3 AT+NETP.................................................................................................... 49

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4.13.2.2.4 AT+UART.................................................................................................... 50
4.13.2.2.5 AT+UARTF..................................................................................................50
4.13.2.2.6 AT+UARTFT............................................................................................... 50
4.13.2.2.7 AT+UARTFL............................................................................................... 51
4.13.2.2.8 AT+TMODE................................................................................................ 51
4.13.2.2.9 AT+WMODE............................................................................................... 51
4.13.2.2.10 AT+WSKEY.............................................................................................. 52
4.13.2.2.11 AT+WSSSID............................................................................................. 52
4.13.2.2.12 AT+ WSLK................................................................................................ 52
4.13.2.2.13 AT+WEBU.................................................................................................53
4.13.2.2.14 AT+WAP....................................................................................................53
4.13.2.2.15 AT+WAKEY.............................................................................................. 54
4.13.2.2.16 AT+HIDESSID..........................................................................................54
4.13.2.2.17 AT+MSLP..................................................................................................55
4.13.2.2.18 AT+WSCAN..............................................................................................55
4.13.2.2.19 AT+ TCPLK...............................................................................................55
4.13.2.2.20 AT + TCPDIS............................................................................................55
4.13.2.2.21 AT+ WANN................................................................................................56
4.13.2.2.22 AT+ LANN.................................................................................................56
4.13.2.2.23 AT+DHCPDEN.........................................................................................57
4.13.2.2.24 AT+ DHCPGW......................................................................................... 57
4.13.2.2.25 AT+ TCPTO.............................................................................................. 57
4.13.2.2.26 AT+ MAXSK..............................................................................................58
4.13.2.2.27 AT+TCPB.................................................................................................. 58
4.13.2.2.28 AT+TCPPTB.............................................................................................58
4.13.2.2.29 AT+TCPADDB..........................................................................................59
4.13.2.2.30 AT+TCPTOB.............................................................................................59
4.13.2.2.31 AT+TCPLKB............................................................................................. 59
4.13.2.2.32 AT+EPHY..................................................................................................59
4.13.2.2.33 AT+STTC.................................................................................................. 60
4.13.2.2.34 AT+DOMAIN.............................................................................................60
4.13.2.2.35 AT+FUDLX................................................................................................60
4.13.2.2.36 AT+MMID.................................................................................................. 61
4.13.2.2.37 AT+IDFIR.................................................................................................. 61
4.13.2.2.38 AT+IDEVE.................................................................................................61
4.13.2.2.39 AT+AABR..................................................................................................62
4.13.2.2.40 AT+RELD.................................................................................................. 62
4.13.2.2.41 AT+Z.......................................................................................................... 62
4.13.2.2.42 AT+MID..................................................................................................... 62
4.13.2.2.43 AT+VER.....................................................................................................62
4.13.2.2.44 AT+H..........................................................................................................62
4.13.2.2.45 AT+ HTTPURL......................................................................................... 63
4.13.2.2.46 AT+ HTTPTP............................................................................................63
4.13.2.2.47 AT+ HTTPPH............................................................................................63

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4.13.2.2.48 AT+ HTTPCN........................................................................................... 63
4.13.2.2.49 AT+ HTTPUA............................................................................................64
4.13.2.2.50 AT+WSSSIDA.......................................................................................... 64
4.13.2.2.51 AT+WSSSIDB.......................................................................................... 64
4.13.2.2.52 AT+WSSSIDC..........................................................................................65
4.13.2.2.53 AT+WSKEYA............................................................................................65
4.13.2.2.54 AT+WSKEYB............................................................................................65
4.13.2.2.55 AT+WSKEYC........................................................................................... 66
4.13.2.2.56 AT+ WSQY............................................................................................... 67
4.13.2.2.57 AT+ HTPMODE....................................................................................... 67
4.13.2.2.58 AT+ HTPSV.............................................................................................. 67
4.13.2.2.59 AT+ HTPTP.............................................................................................. 67
4.13.2.2.60 AT+ HTPURL............................................................................................68
4.13.2.2.61 AT+ HTPHEAD........................................................................................ 68
4.13.2.2.62 AT+ REGEN............................................................................................. 68
4.13.2.2.63 AT+ REGTCP...........................................................................................69
4.13.2.2.64 AT+ REGID...............................................................................................69
5 USR-WIFI232-A2 Usage Introduction....................................................................................................69
5.1 Module Debug................................................................................................................................ 69
5.1.1 Software Debug Tools........................................................................................................69
5.1.2 Network Connection...........................................................................................................70
5.1.3 Debug................................................................................................................................... 70
5.2 Use Cases.......................................................................................................................................72
5.2.1 Wireless Control Application.............................................................................................72
5.2.2 Remote Management Application....................................................................................73
5.2.3 Transparent Serial Port Application................................................................................. 73
5.2.4 Wireless Data Acquisition Card Application................................................................... 74
Appendix B: Disclaimer................................................................................................................................75
Appendix C: History......................................................................................................................................75

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1 Quick Start
USR-WIFI232 series product is used to transmit data between RS232 and WIFI TCPIP
transparently, user can update the product to WIFI control without knowing the WIFI and TCPIP
detail. All the convert work is done by the module. For users, the RS232 side is only as a serial
device,the WIFI side is TCPIP Socket data. User can setup the work detail by sample settings
which can setup via inside web pages or RS232 port. The setup work only need do once, then it
will save the setting forever.
This chapter is a user guide for USR-WIFI232 series products. We suggest users follow the guide
to test module at first, and will have a good understanding of the modules. Users can also choose
the chapter which you are interested in to read. For specific details and instructions, please refer
to the following chapters.
If there are problems in using the process, you can refer to the official website of our application
case:
http://www.usriot.com/Faq/cat-47.html
We can also submit the issue to our customer support center:
http://h.usriot.com
1.1 Hardware connect
In order to test WIFI module, we need connect module RS232 to PC and also WIFI to PC.
In order to test the communication between serial and WIFI network, we need to connect the
serial port to PC, and also connect WIFI networks to PC. Due to the special need both WIFI and
serial, we use PC which add USB WIFI network Card such as the following picture.
Figure 1 hardware connection diagram
About the serial connection, because the module RS232 is 3.3V TTL level, the computer can not
connect to module directly, the user needs to have a TTL to RS232 adapter cable and then
connect to the computer. in order to facilitate the test, we provide USR-WIFI232-A2 evaluation
board for users to choose.

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1.2 Network connection
The following is the USR-WIFI232-A2 module example,Other modules are the same.Open Wi-Fi,
search network, as shown in below, USR-WIFI232-A2_3378(B determined according to the
specific type of module, XXXX is the MAC address after the four) is the default network name
(SSID) of the module.
Figure 2 WIFI Search
Join the network, choose to automatically obtain IP, WIFI module supports DHCP Server feature
and is enabled by default.

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Figure 3 WIFI connection
Now, nlink led of USR-WIFI232-A2 Evaluation Board is lighting.
1.3 communication test
Module’s default setting:
SSID:USR-WIFI232-A2;
Encryption mode:open，none;
UART:57600,8,1,None;
Network parameters：TCP,Server,8899,10.10.100.254;
IP:10.10.100.254;
We just need to follow the parameters of the corresponding set of network communication
parameters, you can make serial <--> WIFI communication, the steps are as follows:
1. Open test software USR-TCP232-Test;
2. COM Settings area (left):
Choose COM port witch has connect the module, there is COM3, choose band rate to 57600, this
is the default band rate of WIFI module, Click Open COM port.
3. Net Settings area (right):
Choose TCP client mode, Server IP write 10.10.100.254, it is the WIFI default IP address, Server
port to 8899, It is the default Port the WIFI module listen, Click Connect to link to the module.
Now, you can test send data between RS232 and WIFI.
COM port to WIFI: PC RS232 -> Module RS232 -> Module WIFI -> PC WIFI.
WIFI to COM port: PC WIFI -> Module WIFI -> Module RS232 -> PC RS232.

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Figure 4 serial / network transmission test
2 Product Overview
2.1 General Description
USR-WIFI232-A2 module is an integration of 802.11 b/g/n wi-fi module,which provide a wireless
interface to any equipment with a Serial interface for data transfer.
The module used to MAC, baseband chip, RF transceiver unit, as well as the power
amplifier;Embedded firmware support wi-fi protocols and configuration, as well as the network
TCP/IP protocol stack.
USR-WIFI232-A2 uses the industry's highest performance embedded industrial structure, and for
the application of smart furniture, smart grid, handheld devices, personal medical, industrial
control, etc. These data fields, do a professional optimization.
USR-WIFI232-A2 as a hot spot can accommodate 32 clients simultaneously wi-fi access, but also
can accommodate 32 TCP client.
2.2 Device Features
Support IEEE802.11b/g/n Wireless Standards
Support TCP/IP/UDP Network Protocols
Support UART/GPIO/Ethernet Data Interface
Support Work As STA/AP/AP+STA Mode

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Support Router/Bridge Mode Networking
Support External Antenna(max 280m)
Support Transparent Transmission Mode
Support AT+ Instruction Set for Configuration
Support Friendly Web Configuration Page
Support Palmodic Signal
Support UART Auto-Frame Function
Single +3.3V Power Supply
FCC/CE Certificated
Support customization
2.3 Device Paremeters
Table 1 USR-WIFI232-A2 Module Technical Specifications
Class
Item
Parameters
Wireless
Parameters
Certification
FCC/CE
Wireless standard
802.11 b/g/n
Frequency range
2.412GHz-2.484GHz
Transmit Power
802.11b: +20 dBm (Max.)
802.11g: +18 dBm (Max.)
802.11n: +15 dBm (Max.)
Configurable
Receiver Sensitivity
802.11b: -89 dBm
802.11g: -81dBm
802.11n: -71dBm
Antenna Option
External:I-PEX Connector
Hardware
Parameters
Data Interface
UART: 300bps - 460800bps
GPIOs
Ethernet: 100Mpbs
Operating Voltage
3.3V (+/-5%)
Operating Current
170mA~300mA
Operating
Temperature
-40℃- 85℃
Storage Temperature
-40℃- 125℃
Dimensions and Size
25×40×8mm
Software
Parameters
Network Type
Station /AP mode/STA+AP
Security Mechanisms
WEP/WAP-PSK/WAP2-PSK
Encryption
WEP64/WEP128/TKIP/AES
Work Mode
Transparent Mode/Serial command

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AT command
AT+instruction set
Network Protocol
TCP/UDP/ARP/ICMP/DHCP/DNS/HT
TP
Max. TCP Connection
32
User Configuration
Web Server＋AT command config.
2.4 Key Application
Remote equipment monitoring
Industrial sensors and controls
Asset tracking and telemetry
Home automation
Medical devices
2.5 Package Information
2.5.1 Recommended Reflow Profile
Figure 5 Reflow Soldering Profile
Table 2 Reflow Soldering Parameter
Note:
1. Recommend to supply N2 for reflow oven.
2. N2 atmosphere during reflow (O2<300ppm).
2.5.2 Device Handling Instruction (Module IC SMT Preparation)
Shelf life in sealed bag: 12 months, at <30℃and <60% relative humidity (RH)
After bag is opened, devices that will be re-baked required after last baked with window time
168 hours.
Recommend to oven bake with N2 supplied.
NO.
Item
Temperature (Degree)
Time(Sec)
1
Reflow Time
Time of above 220
35~55 sec
2
Peak-Temp
260 max

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Baked required with 24 hours at 125 ±5℃before rework process for two modules, one is
new module and two is board with module.
Recommend to store at ≦10% RH with vacuum packing.
If SMT process needs twice reflow:
(1) Top side SMT and reflow (2) Bottom side SMT and reflow
Case 1: Wifi module mounted on top side. Need to bake when bottom side process over 168
hours window time, no need to bake within 168 hours.
Case 2: Wifi module mounted on bottom side, follow normal bake rule before process.
Note:
Window time means from last bake end to next reflow start that has 168 hours space.
3 Hardware Introduction
3.1 Pins Definition
3.1.1 USR-WIFI232-A2 Pins Definition
Figure 6 USR-WIFI232-A2
Figure 7 USR-WIFI232-A2 Pins Map
Table 3 USR-WIFI232-A2 Pins Definition
Pin
Description
Name
Directio
n
Note
1
Ground--GND
GND
Power
Ground
2
VCC 3.3V@350mA
3.3V
Power
3.3V @ 350mA power input
3
UART Data Transmit
UART_TXD
O
If not use UART function,

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this 4 pins can be configured
as GPIO pins, and can
change GPIO pin status
through AT command
GPIO
GPIO3
I/O
4
UART Data Receive
UART_RXD
I
GPIO
GPIO4
I/O
5
UART sends request
of data transmission
UART_RTS
O
GPIO
GPIO5
I/O
6
UART receives data
transmission
permission
UART_CTS
I
GPIO
GPIO6
I/O
7
Module reset signal
RESET
I
“Low ( 0 )” effective reset
input.
The reset duration should be
kept more than 300ms
8
WiFi status Indication
nLink
O
“0”- WIFI connection
available
“1”- No WIFI connection
Can be configured as GPIO.
GPIO
GPIO8
I/O
9
Indicate the module
status of power on
process
nReady
O
“0” or “Palmodic Signal” -
Finish module boot up
process;
“1” - Module boot up not
finish.
Can be configured as GPIO.
GPIO
GPIO9
I/O
10
Restore configuration
nReload
I
Module will Restore factory
default configuration after set
this pin “0” more than 1s,
then set “1”.
GPIO
GPIO10
I/O
11
Ethernet Input+
PHY_RX+
I
+1.8V Ethernet Data
Interface
Support transformer and
direct connection (AC
couple) mode.
12
Ethernet Input-
PHY_RX-
I
13
Ethernet Output+
PHY_TX+
O
14
Ethernet Output-
PHY_TX-
O
3.2 Mechanical Size
USR-WIFI232-A2 modules physical size (25x40mm) as follows:
3.2.1 USR-WIFI232-A2
USR-WIFI232-A2 module Mechanical Size(mm):

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Figure 8 USR-WIFI232-A2 Mechanical Size
3.3 Antenna
3.3.1 External Antenna
USR-WIFI232-A2 modules support external antenna,USR-WIFI232-A2 modules must be
connected to the 2.4G antenna according to IEEE 802.11b/g/n standards.
The antenna parameters required as follows:
Table 4 USR-WIFI232-A2 External Antenna Parameters
3.4 Evaluation Kit
USR provides the evaluation kit to promote user to familiar the product and develop the detailed
application. The evaluation kit shown as below, user can connect to USR-WIFI232-A2 module
with the RS-232 UART port, 100M Eth port or Wireless port to configure the parameters, manage
the module or do the some functional tests.
Item
Parameters
Frequency range
2.4~2.5GHz
Impedance
50 Ohm
VSWR
2 (Max)
Return Loss
-10dB (Max)
Connector Type
I-PEX or populate directly

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Figure 9 USR-WIFI232-A/B module Evaluation Kit
Table 5 USR-WIFI232-A/B Evaluation Kit Interface Description
Function
Name
Description
External
Interface
DC jack
5V power input connector
DB9
Male serial jack of 9-pin,and used to connect to
PC
RJ-45
100M Eth Interface
Module
2x7 2mm DIP connector, connect WIFI module
LED
Power
(Red)
3.3V Power Indicator
TXD
TXD Indicator
RXD
RXD Indicator
Ready
nReady/GPIO Indicator
Link
nLink/GPIO Indicator
Button
Reset
Used to reset the module.
Reload
Module restore to factory default configuration.

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3.5 Hardware Reference Design
3.5.1 Hardware Typical Application
Figure 10 USR-WIFI232-A2 Hardware Typical Application
Notes：
nRST- Module hardware reset signal. Input. Logics “0” effective.
There is 100K Ohm pull-up resister internal up to 3.3V. When module power up or some issue
happened, MCU need assert nRST signal “0” at least 300ms, then set” 1” to keep module fully
reset.
nReady- Module boot up ready signal. Output. Logics “0” effective.
There is 4.7K Ohm pull-up resister internal up to 3.3V. The module will output “0” “or “Palmodic
Signal” after normal boot up. This signal used to judge if module finish boot up and ready for
application or working at normal mode.
nLink- Module WIFI connection indication. Output.
There is 4.7K Ohm pull-up resister internal up to 3.3V. When module connect to AP (STA mode)
or some WiFi STA connect to module (AP mode), the module will output “0”. This signal used to
judge if module already at WiFi connection status.
nReload-Module restore to factory default configuration.Input. Logics “0” effective.
User can assert nReload signal “0” more than 3’s through button or MCU pin, then release,
module will restore to factory default configuration and re-start boot up process. User need add
4.7K~10K Ohm pull-up resister external the module.
UART_TXD/RXD- UART port data transmit and receive signal.
There is 1K Ohm pull-down resister internal. User can’t add pull-up resister at these pins.

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3.5.2 10/100M Ethernet Interface
USR-WIFI232-A/B/C modules provide one 10/100M Ethernet PHY layer interface for data
transition or user configuration. This Ethernet support with transformer and without transformer
(PHY-to-PHY) 2 kinds of connection.
3.5.2.1 Ethernet Connection with Transformer
User board put Ethernet transformer and RJ-45 connector. This is a general 10/100M Ethernet
phy layer connection. The reference design as following:
(Above is for USR-WIFI232-A2 pin type module)
Figure 11 Ethernet Reference Design with Transformer
3.5.2.2 Ethernet Connection without Transformer
For this application, Ethernet will work as internal data transmition interface and save one
transformer and RJ45 connector. Ethernet PHY-to-PHY connection will use AC coupled
connection. This is a space and cost optimized solution. Hardware reference design as following:
Note: VCC signal at reference design shall base on user board PHY chipset voltage level, such
as 2.5V power supply for general Ethernet PHY chipset.
(Above is for USR-WIFI232-A2 pin type module)
Figure 12 Ethernet Reference Design without Transformer

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This module Ethernet interface default is for the application with transformer connection. If you
need PHY-PHY directly connection, please change the hardware as follows:
1. Weld 0 ohm resistance in red position
2. Remove the component in yellow position
BOT side component TOP side component
Figure 13 Schematic resistance changes
Specific PHY-PHY direct connection reference to user manual chapter 1.3.2.2 application of
Ethernet without transformer and AT+FEPTP command
The command:
AT+FVEW=enable<CR> to open ethernet WAN port function
Remark:
1. Only when ethernet as WAN, this command is needed. Module default LAN port.
2. After this command, make sure module WAN IP and LAN IP in different segment. (Modify the
ALN IP in AP Settings, modify the WAN IP in STA Settings)
AT+FEPTP=on<CR> Quey/set default ethernet PHY-PHY on/off
AT+FEPHY=on<CR> Open ethernet function permanently
AT+RELD<CR> Command with “F” need to be affective after AT+RELD
After module reset, command effect, then will not impact by Reload
For user’s design, pls note:
1. Cable connection should be AC coupling, your cable need be pulled up to VCC (fit with PHY
chip level)
2. Cable TX connected to RX. In PHY-PHY direct connection, PHY chip dose not support
direct/ cross self-adaption
3.Your PHY chip on board should better to be forced into 100M work mode
3.5.3 UART Interface
UART interface is the serial data transmition interface mainly used for USR-WIFI232-A2 modules.

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User can add RS-232 chipset on user board and convert the signal to RS-232 voltage to
communicate with outside equipment or sensors. USR-WIFI232-A2 modules UART interface
include 4 general signals: TXD/RXD/RTS/CTS. The hardware reference design with RS-232
chipset as following:
Figure 14 Figure 10 UART Interface Reference Design
Notes: TXD pin is also hardware configuration pin internal module. So this pin MUST pull-down
during module power up. USR-WIFI232-A2 modules provide internal pull-down resister, user can’t
add pull-up/pull-down resister on user board, which may cause module can’t work.
3.5.4 Power Interface
USR-WIFI232-A2 module support single +3.3V power supply. The peak current shall about
350mA and normal WiFi working current shall about 200mA. The power save (WiFi OFF) mode
will about 100mA
Decoupling at power pin suggested, At least one 100uF and one 10uF capacitor required at user
board and put near module power input pin will increase the reliability and performance.
4 Modules Function Description
4.1 User configuration process
After USR-WIFI232-A2 module electric starter, based on user pre-set parameters, automatically
connect to wireless networks and servers, and enter the working mode is set to open in
accordance with the default serial port parameters.
The parameters which need to configure include:

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Wireless Network Parameters
Wireless Network Name（SSID）
Security Mode
Encryption Key
TCP/UDP Linking Parameters
Protocol Type
Link Type（Server or Client）
Target Port ID Number
Target Port IP Address
Serial Port Parameters
Baud Rate
Data Bit
Parity (Check) Bit
Stop Bit
Hardware Flow Control
Work Mode Selection
Transparent mode/Serial command mode/GPIO mode
The following sections will introduce specific to each part in detail.
4.2 Working mode
4.2.1 Transparent Mode
USR-WIFI232-A2 modules support serial interface transparent transmission mode. The benefit of
this mode is achieves a plug and play serial data port, and reduces user complexity furthest. In
this mode, user should only configure the necessary parameters. After power on, module can
automatically connect to the default wireless network and server.
As in this mode, the module's serial port always work in the transparent transmission mode, so
users only need to think of it as a virtual serial cable, and send and receive data as using a
simple serial. In other words, the serial cable of users’ original serial devices is directly replaced
with the module; user devices can be easy for wireless data transmission without any changes.
The transparent transmission mode can fully compatible with user’s original software platform
and reduce the software development effort for integrate wireless data transmission.
Notes: Users also open the serial port hardware flow control (CTS/RTS) function, so that we can
make the bit error rate to a minimum.If the user doesn't need hardware flow control function of the
serial port, only need to the corresponding pin foot (CTS/RTS) hung up.