Tunnel – Periodically obtaining readings from 5 electronic meters and sending them to a webserver using the ModBus RTU protocol

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Scenario details:

  • We have 5 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 5 meters to read the records via a serial port. The records to be read are for the cumulative consumption (record nº20) and for average consumption (record nº 21)
  • After every reading 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 there is a communication failure with the 2G/3G/4G so that it can send 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 MTX-Tunnel at any moment to be able to read PLC records in real time as well as being able to write them and modify the PLC configuration records

Solution: MTX-Tunnel firmware + MTX-Java-IoT/MTX-Java-T/MTX-Java-T2

Config.txt configuration file:

Configuration Observations
COMM2_baudrate: 9600
COMM2_bitsperchar: 8
COMM2_autorts: off
COMM2_autorts: off
COMM2_stopbits: 1
COMM2_parity: none
GPRS_apn: movistar.es
GPRS_login: MOVISTAR
GPRS_password: MOVISTAR
GPRS_timeout: 0
MTX_PIN: 0000
MTX_mode: none
MTX_model: MTX-4G-JAVA-IOT-STD-N
MTX_portAux: modbusmaster
MTX_TPProtocol: ntp
MTX_TPServer: ntp.roa.es
MTX_TPServer2: es.pool.ntp.org
MTX_ping: 35
MTX_pingIP: 8.8.8.8
SMS_allPhones: on
SMS_sendIP: on
SMS_ATEnabled: on
SMS_ATResponse: on
FIREWALL_enabled: off
TELNET_enabled: on
TELNET_login: user
TELNET_password: 1234
TELNET_firewall: off
LOGGER_enabled: on
LOGGER_password: ID00001
LOGGER_server: www.miservidorWeb.com/json.asp?data=
LOGGER_registerSize: 300
LOGGER_numRegistersFlash: 1500
LOGGER_httpMode: getjson
MODBUS_address: 1;2;3;4;5
MODBUS_start: 20
MODBUS_numwords: 4
MODBUS_readCommand: 3
MODBUS_period: 900		 Serial port (where internal GPS is connected) 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
SIM Card PIN
MTX-Tunnel mode
MTX modem model
AUXILIAR COM port used as master modbus
Time synch. protocol
Time server
Backup time server
Ping every 35 minutes without comms
IP address to ping
All phone numbers are authorized
IP sent to phone which called or “on” SM
Remote AT commands by SMS enabled
Modem response to AT command with SMS
Any IP will be able to connect to the modem
Telnet is activated
Telnet login
Telnet password
Telnet port 20023
We enable the MTX Logger, to store the records
Password field can be used as ID device
Server URL, will receive JSON data
Register size
Maximum number of records in MTX
HTTP GET (JSON) mode
ModBus equipment address
ModBus register address to be read
Number of registers read
Reading command
Timing -seconds- read is repeated

Details:

  • 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 the record cannot be sent (if there is no GPRS coverage or the server fails), it will store the data to memory in order to send it later on. With Telnet you can connect to the equipment directly 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)
  • A JSON object sent to a specified URL in LOGGER_server is encoded in the following manner for example:
{“IMEI”:353234028103206,”P”:”ID00001”,”TYPE”:”MODB”,”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.