Chengdu ebyte electronic Technology Co.,Ltd.
E840-TTL-GPRS03 User Manual
Copyright ©2012–2017
，
Chengdu ebyte electronic Technology Co.,Ltd.
15
AT+CREG
Function
：
Check if it is registered to the carrier.
Format
：
Set
TX AT+CREG<CR><LF>
Return <CR><LF>+OK=<creg><CR><LF>
Parameter
：
creg
1
Network registered
2
Network not registered
Description
：
None
AT+CPIN
Function
：
Query SIM status
Format
：
Set
TX AT+CPIN<CR><LF>
return <CR><LF>+OK=<cpin><CR><LF>
Parameter
：
cpin
1 SIM card detected
0 SIM card not detected
Description
：
None
7. Notes
The Socket link of this module will always be opened. After the initialization is successful, it will automatically
establish a connection with the configured network server.
After the module is powered on, it cannot be initialized successfully. That is, the State indicator has no indication
for more than 30 seconds. In this case, check whether the module is installed properly, whether the SIM card is
properly inserted, and whether the SIM has failed.
Short connection can be used to reduce the connection pressure of multiple devices to the server. When the short
connection function is enabled (AT+SHORTM>2), the module will actively disconnect the connection when the
network or serial port has no data duration exceeding the short connection setting period. After the
disconnection, the network cannot send data, and the local serial port sends valid data, the module will
immediately establish a connection with the server. If the local clear cache function is turned off, the packet will
be cached (maximum 10K bytes). After the connection is successful, the data will be sent to the server. The
local cache function is cleared and the packet will be discarded.
The heartbeat function is used to maintain the connection after the module and the server are successfully
connected. In the network, if the client and the network server successfully establish a connection and there is
no data transmission for a long time, the Socket link may appear “dead”, that is, the chain exists but cannot
send and receive data. Therefore, in actual use, it is recommended to enable the heartbeat packet function to
ensure the reliability of the network link.
In actual use, it is normal for the data delay of the two communications to be different.
When the device serial port outputs the words “pdp error, device will be reset!”, it indicates that the PDP context is
disabled by the network. The SIM card may be loose or the current network channel is occupied abnormally.