Ebyte E840-DTU User Manual page 12

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AT mode：under this mode all UART data is considered as AT command.
c)
d) Mode switch ，In the transparent transmission mode, after the serial port receives the "+++" frame data, the
RX pin receives any AT command within 3 seconds, and the mode switches to the AT mode. In AT mode,
send AT+EXAT<CR><LF> to switch to transparent transmission mode.
2、Network function
a) Short connection: In TCP Client mode, the short connection function is enabled. If there is no data reception in the
serial port or network port within the set time, the network connection will be automatically disconnected. The short
connection function is turned off by default. The connection time can be set from 2 to 255 seconds. When set to 0, the
short connection function is disabled.
b) Registration package: The registration package is closed by default. The user can configure 4 types of registration
packages. You can choose to send the physical address (IMEI code) when connecting, send custom data when connecting,
add the physics before the connection and each packet of data. Custom data is added to the address, connection time, and
data before each packet. The maximum length of the custom registration packet is 40 bytes (when set to HEX format, the
maximum length is 20 bytes).
c) Heartbeat packet: In the idle state of network communication, the heartbeat packet is used for network state
maintenance. The heartbeat period can be set from 0 to 65535 seconds, and the maximum length of the heartbeat packet
is 40 bytes (when set to HEX format, the maximum length is 20 bytes). Supports two heartbeat types: network heartbeat
and serial heartbeat. When the network heartbeat is selected, the communication idle time starts, and the heartbeat data
packet is sent to the server according to the configured heartbeat period. Select the serial port heartbeat, start timing
with communication idle, and send heartbeat packets to the serial port according to the configured heartbeat period.
d) Clear the cache: Before the connection to the server is established, the data received by the serial port will be
cached. When the connection with the server is established, you can choose whether to clear the cached data. By default,
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E840-DTU(4G-02E) User Manual
12