Modbus is communication protocol developped in 1979. It is still very used.
The official specifications are here : www.modbus.org/specs.php
This article is also very usefull to understand the protocol : http://www.simplymodbus.ca/
Prior to configure Modbus, you have to connect a gateway to Pilot Things.
Depending of the gateway you may use Modbus on serial port or TCP. Pilot Things driver supports the 2 modes.
To configure Modbus, goes into Pilot Things network menu, select your gateway and drill down configuration.
Modbus on TCP
Pilot Things driver acts as a Modbus Master. In order to connect a slave to Pilot Things you must determine an IP address. This IP will be configured on the Ethernet port of the gateway.
The available parameters are:
| Mandatory | Parameter | Example | Description |
| Yes | name | "name":"Controller1" | Name of the controller in Pilot Things |
| Yes | serial | "serial":false | Must be false for Modbus on TCP |
| Yes | host | "host":"192.168.10.10" | IP address of the controller |
| Yes | port | "port":502 | must be 502 |
| Yes | endianess | "endianess":"little_endian" | "little_endian" (exemple M2M1) or "big_endian" (exemple M1M2) |
| Yes | pollingFrequency | "pollingFrequency":120 | ? in millisecond |
| Optional | controlWordAddress | "controlWordAddress":42100 | |
| Optional | controlWordPollingFrequency | "controlWordPollingFrequency":60 | |
| Yes | defaultThingName | "defaultThingName":"Thing test" | Default thing name if not specified in the register configuration |
Modbus RTU on serial
Base on the configuration, Pilot Things will configure the serial port.
The available parameters are:
| Mandatory | Parameter | Exemple | Description |
| Yes | name | "name":"Controller1" | Name of the controller in Pilot Things |
| Yes | serial | "serial":true | Must be true for Modbus RTU |
| Yes | portName | "portName":"/dev/ttyHSL0" | Example for Sierra FX30S |
| Yes | baudRate | "baudRate":"9600" | Serial baud rate |
| Yes | flowControlIn |
"flowControlIn":"0" |
Used for flowControl In |
| Yes | flowControlOut |
"flowControlOut":"0" |
Used for flowcontrol out |
| Yes | databits |
"databits":"8" |
Serial databits |
| Yes | stopbits |
"stopbits":"2" |
Serial stopbits |
| Yes | parity |
"parity":"0" |
0 for no parity 1 for parity |
| Yes | encoding |
"encoding":"rtu" |
Must be rtu |
| Yes | endianess | "endianess":"little_endian" | "little_endian" (exemple M2M1) or "big_endian" (exemple M1M2) |
| Yes | pollingFrequency | "pollingFrequency":120 | Modbus server polling frequency in millisecondes |
| Optional | controlWordAddress | "controlWordAddress":42100 | |
| Optional | controlWordPollingFrequency | "controlWordPollingFrequency":60 | |
| Yes | defaultThingName | "defaultThingName":"Thing test" | Default thing name if not specified in the register configuration |
Modbus registers configuration
After TCP or RTU configuration, you must map each used register to a Thing.
The available parameters are:
| Mandatory | Parameter | Exemple | Description |
| Yes | thingName |
"thingName": "Thing A" |
Thing's name created in Pilot Things |
| Yes | slaveId |
"slaveId": 1 |
The id of slave who contains register |
| Yes | name |
"name": "registerA" |
Register name. Used for information only |
| Yes | registerAddress |
"registerAddress": 42040 |
Modbus register address |
| Yes | readable |
"readable": true |
Register readable |
| Yes | writable |
"writable": false |
Register writable |
| Yes | format |
"format" : "unsigned short" |
Modbus register format, possible values are:
|
| Yes | length |
"length": 2 |
Possible values are:
|
| Optional | pollingFrequency |
"pollingFrequency": 10000 |
if not specified Modbus server polling frequency is used (in millisecondes) |
| Optional | responseTimeout |
"responseTimeout": 4000 |
Modbus server try 3 times for each timeout |
What's next ?
Have a look of this article for a configuration example : Modbus configuration example
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