User's Manual

HF-A21-SMT Embedded WiFi Module User Manual
Shanghai High-Flying Electronics Technology Co., Ltd
www.hi-flying.com
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When module enables AP+STA function, Module‟s STA interface can connect with router and
connect to TCP server in the network. At the same time, module‟s AP interface is also active and
permit phone/PAD to connect through TCPB, then phone/PAD can control user device and and
setting the module parameters,
The advantage of AP+STA mode is:
 Users can easily setting and track user device through Phone/PAD and not change the
orginal network setting.
 Users can easily setting module‟s parameters through WiFi when module works as STA
mode.
AP+STA Mode Setting:
AP+STA mode need serial AT command to enable as follows:
 AT+FAPSTA=on, Enable AP+STA mode;
 Then, when you configure module works as STA mode, it‟s AP interface still active;
AP+STA Mode Notes:
When user enable AP+STA function, the STA port need to keep connected with other router (AP),
or STA port will have to scan the AP frequently, which will affect AP port function and may cause
some data loss.
So,if user confirm STA port can‟t connect with AP at some time, user can disable the STA scan
through the following command:
 AT+STTC=on/off，on: Scan AP; off: No scan AP.
After re-start module, this command not saved;
 AT+FSTTC=on/off;
This command is saved after re-starting the module;
2.2. Auto- Frequency Function
When module works as STA, HF-A21-SMT will adjust its wireless channel to keep the same
channel with associated AP and connect in.
When module works as AP and HF-A21-SMT enable Auto-frequency function, then when module
boot up, it will select the best wireless channel based on surrounding environment.
2.3. Security
HF-A21-SMT module supports multiple wireless encryption mechanisms, and enables to protect
the security of user‟s data transmission, the mechanisms include:
 WEP
 WPA-PSK/TKIP
 WPA-PSK/AES
 WPA2-PSK/TKIP
 WPA2-PSK/AES
2.4. UART Frame Scheme
2.4.1. UART Free-Frame
HF-A21-SMT support UART free-frame function. If user select open this function, module will
check the intervals between any two bytes when reciving UART data. If this interval time exceeds
defined value (50ms default), HF-A21-SMT will think it as the end of one frame and transfer this
free-frame to WiFi port, or HF-A21-SMT will receive UART data untill 4K bytes, then transfer 4KB
frame to WiFi port.