Tunnel – An advanced example for reading 2 serial devices using a single modem/SIM and simultaneously using GPRS connection and GSM calls. There is additional serial tunnelling when there are no GSM/GPRS connections

Scenario details:

• In this scenario you have a modem with 2 serial ports. One serial port is connected to an energy meter; the other is connected to a PLC
• When there is no GPRS connection with the modem and a GSM call has not been established by the operator, the modem acts as a serial tunnel. This means that all data that arrives at the modem from the PLC must be redirected to the energy meter and vice versa – all serial data that the energy meter sends should be redirected to the PLC
• You should be able to establish 2 GPRS-serial gateways that function at the same time. Through one you will have access to the electric meter to take readings periodically; through the other you should be able to have access to modbus records from the PLC
• Additionally, the energy operator (Iberdrola, Endesa, etc.) will make a daily GSM call in order to read the meter’s data. This GSM call must be a priority, freezing GPRS connections until the call is finished

Config.txt configuration file:

Configuration

Observations

COMM_baudrate: 9600 COMM_bitsperchar: 8 COMM_autorts: off COMM_autorts: off COMM_stopbits: 1 COMM_parity: none COMM2_baudrate: 9600 COMM2_bitsperchar: 8 COMM2_autorts: off COMM2_autocts: off COMM2_stopbits: 1 COMM2_parity: none GPRS_apn: movistar.es GPRS_login: MOVISTAR GPRS_password: MOVISTAR GPRS_timeout: 0 GPRS_mode: 2G MTX_mode: server MTX_model: MTX65i MTX_ping: 35 MTX_pingIP: 8.8.8.8 MTX_radioBand: europe MTX_portAux: gateway MTX_port: 20010 Firewall_enabled: off CSD_enabled: on Telnet_enabled: on Telnet_port: 20011 Telnet_bypass: on

Serial port baud rate Number of bits No flow control No flow control 1 stop bit No parity Serial port baud rate Number of bits No flow control No flow control 1 stop bit No parity APN GPRS from your network operator GPRS Login GPRS Password Modem is always GPRS connected IMPORTANT. For GSM call, 2G is needed MTX-Tunnel mode MTX terminal modem Ping every 35 minutes without comms IP address to ping If modem is installed in Europe Tunnelling between ports Establish GPRS Gateway, read the energy meter Accepts incoming connections from any IP Accepts GSM calls from energy operator Enabled as a secondary Gateway for PLC access TCP port receiving connections to access PLC Set to “on” to use Telnet as a second Gateway

Details:

• This example uses Telnet as a secondary gateway. If the secondary gateway does not need to be established, you could use Telnet for remote configuration and monitoring
• If you use Telnet as a secondary Gateway (as shown throughout the example) you can still have remote access to the modem with the embedded commands between the tags  or simply via SMS commands. For example, via SMS you can check the modem’s coverage and change or read a configuration