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BeamOS – Modbus

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Summary

Modbus is a serial communications protocol. Simple and robust, it has become a de facto standard communication protocol and is now a commonly available means of connecting industrial electronic devices. This chapter is an overview of the Modbus TCP functionality for BEAM devices.

Modbus TCP

Modbus TCP provides users with the possibility to set or get system parameters. The Modbus daemon acts as slave device. That means it accepts connections from a master (client) and sends out a response or sets some system related parameter in accordance with the given query.

The figure below is an example of the Modbus TCP window section and the table below provides information on the fields contained in that window:

BeamOS services modbus modbus tcp screen
Field Name
Value
Description
Enable
yes | no; default: no
Turns Modbus TCP on or off.
Port
integer [0..65535]; default: none
TCP port used for Modbus communications.
Allow Remote Access
yes | no; default: no
Allows remote Modbus connections by adding an exception to the device’s firewall on the port specified in the field above.
Mobile Traffic Usage Logging
yes | no; default: no
Enables Mobile Traffic Usage Logging (can also be enabled from Status → Mobile Traffic → Configuration). This is required in order to read mobile data usage information from Modbus registers.

Get Parameters

Modbus parameters are held within registers. Each register contains 2 bytes of information. For simplification, the number of registers for storing numbers is 2 (4 bytes), while the number of registers for storing text information is 16 (32 bytes). The register numbers and corresponding system values are described in the table below:

required value
register number
number of registers
representation
System uptime
1
2
32 bit unsigned integer
Mobile signal strength (RSSI in dBm)
3
2
32 bit integer
System temperature (in 0.1 °C)
5
2
32 bit integer
System hostname
7
16
Text
GSM operator name
23
16
Text
Router serial number
39
16
Text
LAN MAC address
55
16
Text
Router name
71
16
Text
Currently active SIM card slot
87
16
Text
Network registration info
103
16
Text
Network type
119
16
Text
Current WAN IP address
139
16
32 bit unsigned integer
data usage values*
Mobile data received today
135
2
32 bit integer
Mobile data sent today
137
2
32 bit integer
Mobile data received this week
141
2
32 bit integer
Mobile data sent this week
143
2
32 bit integer
Mobile data received this month
145
2
32 bit integer
Mobile data sent this month
147
2
32 bit integer
Mobile data received in the last 24 hours
149
2
32 bit integer
Mobile data sent in the last 24 hours
151
2
32 bit integer
Mobile data received in the last 7 days
153
2
32 bit integer
Mobile data sent in the last 7 days
155
2
32 bit integer
Mobile data received in the last 30 days
157
2
32 bit integer
Mobile data sent in the last 30 days
159
2
32 bit integer
 
* All received/sent data usage values are returned in kibibytes (KiB), which is an ISQ standard accepted by most major standard organizations.
1 kibibyte (KiB) = 210 bytes = 1024 bytes
1 mebibyte (MiB) = 210 kibibytes (KiB) = 220 bytes = 1 048 576 bytes

Get Parameters

The Modbus daemon can also set some device parameters. These parameters and explanations on how to use them are described in the table below:

value to set
register number
register value
description
Switch WiFi (ON/OFF*)
210
1 | 0
Turns WiFi ON or OFF
Switch mobile data connection (ON/OFF*)
211
1 | 0
Turns mobile data connection ON or OFF
Change APN
213
APN code
Changes APN. The number of input registers may vary depending on the length of the APN, but the very first byte of the set APN command has to be specified as 1
Reboot
220
1
Reboots the router

* All ON/OFF commands only accept 0 and 1 values, which represent the following:

  • 1 – ON
  • 0 – OFF
Previous BeamOS – Auto Reboot
Next BeamOS – UPNP
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