The MTX-65i and MTX-3G-JAVA modems are used in infinite applications. Java avoids the use of external processor boards, which saves space and money. The MTX-65i and MTX-3G-JAVA modem terminals have been used in plenty of telemetry applications/scenarios. Java programmability avoids the use of external processor boards, saving space and costs. MTX-TUNNEL software is ready to use in ModBUS application scenarios as an example.


Telemetry solution MTX M2MPeriodically obtaining readings from five electronic meters and sending them to a Web Server using the ModBUS RTU protocol.

Scenario details

  • We have five electric meters with ModBUS RTU protocol. These meters have a series of readings in their internal memory (e.g. cumulative consumption and average consumption) which should be read and sent to a Web server periodically.
  • Therefore every 15 minutes the MTX-Tunnel has to question the five meters to read the records via a serial port. The records to be read are those of the cumulative consumption (record nº20) and the average consumption (record nº 21).
  • After every reading, the MTX tunnel has to send the records to a web server via HTTP GET using a JSON object. However, it must be able to store up to 1500 readings in flash memory in case of a communication failure with the GPRS, sending them when the connection is restored. For each meter, it will send a JSON frame where it indicates the ModBUS address/ identifier of the meter that has been read.
  • You need to be able to access the MTX-Tunnel at any moment to be able to read as well as write PLC records in real time, and modify the PLC configuration records.


  1. The summary of this example is as follows: The modem will periodically read, every 15 minutes, two ModBUS records from each counter and they will be sent to a web server via a JSON object (to the URL specified in the LOGGER_server parameter). In the event that you are not able to send the record (if there is no GPRS coverage or the server fails), it will store the data to memory and send it later on. With Telnet you can directly connect to the equipment in order to check/change the PLC records in real time (for this, search for the AT^MTXTunnel=getmodbus and AT^MTXTUNNEL=setmodbus commands in this manual).
  2. The JSON object sent to a specified URL in LOGGER_server is encoded in the following manner (as an example): {“IMEI”:353234028103206,”P”:”ID00001″,”A”:1,”TS”:”20/04/13 08:31:44″,”V1″:23,”V2″:275} This means that the web Server receives a JSON object with the modem’s IMEI (IMEI), the password field (P), which can be used to identify the computer if you do not want to use the IMEI, the counter’s ModBUS address (A) which distinguishes the counter that relates to the readings, the time stamp (TS) which indicates when the ModBUS data has been read by each counter, and “V1”/”V2” which indicates the readings that have been taken.

Telemetry MTX Tunnel solution