Data transmission mode: GPRS Modems can be set to different operating modes to meet the requirements of different user applications. Under different operating modes, GPRS ModemsÂ position in GSM / GPRS communication system platform is not the same.
Transparent transmission mode: The device does not resolve any data received from the serial port directly to the data as TCP or UDP data package sent, and specific analytical data are collected by the back-end data terminal equipment or by the relevant server data center deal with.
Transparent mode of transmission is the most widely applicable range, the most versatile mode of operation. In transparent transmission mode, the device does not resolve any data received from the serial port directly to the data as TCP or UDP data package sent, and specific analytical data were collected relevant data terminal equipment and the front end of the back-end data center server for processing. The appliance operates in transparent mode, data transmission equipment and monitoring center using TCP Socket connection to the data format to be transmitted is stipulated by the backend of various industrial instrumentation and monitoring center application services good, the equipment does not concern. Therefore, for different applications, the device has a plug and play feature, other devices if the system has no special agreement, the operating mode is recommended.
In order to meet the requirements of SCADA system, under Modbus TCP mode also provides a range of communications security measures: configuration command string reverse control terminal acquisition equipment, according to user needs to change the way of working terminal acquisition equipment; defined data framing a manner that the device directly The data in the format required by the provisions of the package into a frame, and then transferred to the host computer via TCP / UDP. Set all aspects of the baud rate, IP address registration, timed restart, set the buffer size, hardware-based flow control.
In transparent mode, established by the TCP protocol data link can also be connected as long as the short connection. When the long connection, data transmission terminal will remain connected to the data center, once the link is broken and the central data transmission terminal automatically re-establish the connection, the device remains online; when the short connection, data transmission terminal in a time period (eg: 5 minutes) Automatic data flow monitoring data communications within, when there is no data traffic within this time frame, the number of transmission equipment to disconnect the connection and exit the GPRS network, in order to enable data transmission equipment activated again, through SMS, telephone dialing (when SIM card must support digital transmission equipment voice call function), the next crew took the initiative to write the serial data of these two methods, the equipment on the line again, with the center to establish a connection for data communications.
The formation of a transparent transfer mode network is very simple, you need to set the basic parameters for GSM Modems with local / distal manner, while the data acquisition device with RS232 / 485 interface can be; Once in transparent mode, the terminal equipment and the central data server to establish C / socket mode S structure TCP / IP link, the user terminal device is now already have a function in the two-way transmission of data on the Internet network, making the data acquisition device converts serial devices over Ethernet.
Command mode: If the user’s terminal can output AT command set, you can put Modem GPRS DTU as a TCP / IP protocol stack to use with. Users can output terminal device AT commands, through its serial port, dial-up PPP to send as GPRS DTU, to establish a TCP socket connection to send and receive data in the AT command.
In all instruction set standard MODEM AT commands are prefixed, referred to AT commands. There are many industrial, financial sector data terminal products directly output AT command, control external devices, or user-developed single-chip system, the application software supports the AT command set. In this case, the user can extend MODEM GPRS Modems seen with a TCP / IP functionality, GPRS DTU from the serial port to receive data from the user terminal sent by the AT command set, and perform the appropriate action. GPRS Modems supports all standard AT commands, mainly used to control GPRS module; GPRS Modems while also depending on the application, enabling advanced applications GPRS function command: For example: Set GSM Modems communication parameters, activation / disconnect GPRS connection, send / receive short message, activate / terminate the TCP connection, send / receive TCP packets, send / receive UDP packets. The AT command set of advanced applications, users can refer to the corresponding GPRS module AT command set provided by the supplier documentation, in order to achieve the second development of user data terminal equipment.
SMS mode: GSM Modems central server in the user side, the serial port directly connected to SMS server. Receive and send messages using GSM network equipment, complete the short message codec, and the SMS server serial transmission via short message content.
To enter text mode, the first premise is command mode, switch to text mode by mode conversion command, this time as GPRS Modems as Modem can receive all the AT commands, execute the corresponding function.
In this mode, GPRS Modems in user on the server side, the serial port directly connected to SMS server. Receive and send messages using GSM network equipment, complete the short message codec, and the SMS server serial transmission via short message content.
There are two short messaging encoding, are text mode and PDU encoding, in a short message to the PC as a hardware platform for server if received directly from the GPRS Modems module, you need to complete their work codec short message.