Intercel eSAM User manual
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Modbus is a standardized and widely used protocol for connecting industrial devices and sensors. Because of its
versatile design, Modbus packets can be sent over many different communication channels.
The eSAM and Ultra eSAM support Modbus packets using either TCP/IP or RS232. The eSAM is capable of linked
Modbus devices across the 4G mobile network, as well as over the local network.
This guide will explain how to connect two serial Modbus devices using two eSAM modems.
The Modbus protocol is somewhat unique in that it can be communicated using multiple different protocols. This
means that you could have a Modbus Master which uses TCP/IP to carry signals, and a slave with uses RS232. The
eSAM is able to bridge these two networks such that TCP/IP Modbus devices and RS232 Modbus devices can
communicate.
For those familiar with the Client / Server model for networking, the Master / Slave system used by Modbus might
seem backwards. In Client/Server, the Client needs to know the IP Address of the Server, so it can send requests to it.
The Server then replies to these requests, so it does not need to know the IP Address of the Client beforehand.
In the Master/Slave system, the Master sends requests to the Slave which the Slave then responds to. This means
that the Master must know the IP of the Slave ahead of time, and that the Slave does not need to know the IP of the
master. As a result, the Slave device must be configured with a public IP address, or an sssIP address accessible to
the Master using a VPN or other networking technology.
If you have any queries regarding the eSAM, please contact Intercel technical support at intercel@intercel.com.au.
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This guide will walk you through configuring your eSAM modem to work with Modbus devices.
1. Use your web browser to connect to the eSAM. By default, this can be done by connecting your computer to
the eSAM’s Ethernet port and entering the IP Address http://192.168.1.1 into your web browser. You should
be presented with the screen below
2. Log into the eSAM. The default login details are:
Username: admin
Password: admin
(You should change these details for security reasons.)
3. Insert the SIM Card, connect the modem’s antenna and then enter the APN as described in the eSAM
QuickStart guide. Please contact Intercel technical support at intercel@intercel.com.au if you encounter any
issues at this stage.
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4. Open the ‘Applications > DTU/Modbus’screen. This screen controls the bridging of TCP/IP packets onto the
Serial RS232 or RS485 line.
Configure this screen as follows:
a. Press ‘Enable’to activate the DTU service.
b. Select ‘Modbus’as connection type.
c. Set the work mode to ‘modbus_rtu_slave’or ‘modbus_ascii_slave’,depending on whether your
Modbus device uses RTU or ASCII encoding.
d. Set the local port to an unused port, or to whichever port is being used by your Modbus master
equipment. In this example, we have chosen port 6000.
e. Set the RS232/RS485 settings to match those used by your serial Modbus slave device.
5. Connect your Serial device to the modem.
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6. Open the Status>Modem menu. Write down the IP address assigned to your modem. We will need to provide
this address to the Modbus Master, so it knows where it has to send packets to contact the Modbus Slave.
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This guide will walk you through configuring your eSAM modem to work with Modbus devices.
1. Use your web browser to connect to the eSAM. By default, this can be done by connecting your computer to
the eSAM’s Ethernet port and entering the IP Address http://192.168.1.1 into your web browser. You should
be presented with the screen below
2. Log into the eSAM. The default login details are:
Username: admin
Password: admin
(You should change these details for security reasons.)
3. Insert the SIM Card, connect the modem’s antenna and then enter the APN as described in the eSAM
QuickStart guide. Please contact Intercel technical support at intercel@intercel.com.au if you encounter any
issues at this stage.
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4. Open the ‘Applications > DTU/Modbus’screen. This screen controls the bridging of TCP/IP packets onto the
Serial RS232 or RS485 line.
Configure this screen as follows:
a. Press ‘Enable’to activate the DTU service.
b. Select ‘modbus’as connection type.
c. Set the work mode to ‘modbus_rtu_master’or ‘modbus_ascii_master’,depending on whether your
Modbus device uses RTU or ASCII encoding.
d. Enter the IP of your modbus slave device. This address will have been noted down from the previous
section of this guide
e. Enter the port to match that of your modbus slave. This must match the port of the device you want to
connect to.
f. Set the RS232/RS485 settings to match those used by your serial Modbus slave device.
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5. You will now have a bridge between the Modbus master on one eSAM, and the Modbus slave on the other
eSAM. Please configure your Modbus devices as required.
Please consult the manufacturer of your Modbus equipment for advice on configuring your Modbus hardware.
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