NOVUS myPCProbe - Manual (Page 10)

myPCProbe
NOVUS PRODUTOS ELETRONICOS LTDA www.novusautomation.com 10/11
APPENDIX 1 – SERIAL COMMUNICATION PROTOCOLS
Each myPCProbe module installed in a PC is accessible as a distinct serial COM port. A module can communicate in
one of two protocols: ASCII (delimited text) or Modbus RTU. Any program with serial communication capability using one
of these protocols may be used to gather measurement data from the modules.
The used communication protocol depends on the “auto-send” module configuration. See the software help for
information on how the change the “auto-send” configuration.
•
Auto-send disabled: Communicates using Modbus RTU protocol. The module is a slave that responds to read
requests issued by a Modbus master (for example a SCADA software).
•
Auto-send enabled: Communicates using ASCII (delimited text) protocol. The module transmits continuously the
values measured in its channels, in text format.
The module can only be configured using the myPCLab software.
The serial COM port assigned to a device will only be available a few seconds after connection of the
myPCProbe module to a USB port, since Windows operating systems needs to load the appropriate
drivers. To check the COM port assigned to each module, use the myPCLab software or go to the
Windows Control Panel in:
Control Panel/System/Hardware/Device Manager/Ports (COM & LPT)
MODBUS RTU (AUTO-SEND MODE DISABLED)
myPCProbe is a Modbus RTU slave that can answer to “Read Holding Register” requisitions, Modbus command number
3. The module doesn’t have a specific Modbus address, since it’s the only device in its serial port. It will answer to read
request to any valid slave address.
When configuring the serial communication parameters of the Modbus master, set the COM port number assigned to the
device. The USB port ignores all other serial communication parameters.
•
Communication Port: Select the COM port number assigned to the myPCProbe.
•
Baud rate: any
•
Number of data bits: any
•
Stop bits: any
•
Parity: any
The following table shows the Modbus registers available for reading. Three different address formats are presented.
Use the address format according to your Modbus master.
Modbus Address (in 3 different formats)
Protocol, 0 based Protocol, 1 based PLC Content
4 5 40005 Channel 1 value
5 6 40006 Channel 2 value (RHT model)
6 7 40007 Ambient temperature value (TEMP model)
Holding Registers Table (reference 4X)
•
Channel 1 and 2 values
Current value of the input channel, in engineering units. For values with decimal places, the decimal point
separator will be omitted. Example: A channel with value 13.9 will be read as 139.
Measured values above or below its specified limits will be replaced by the corresponding overflow or underflow
values, according to the module configuration.
A disabled channel will return 0 (zero) as its measured value.
•
Ambient Temperature Value
Current measurement from the internal ambient temperature sensor, in degrees Celsius or Fahrenheit, according
to module configuration. The decimal point separator is omitted. Example: 23.8°C is read as 238.
Never send a Modbus write command to a module. Configuration or calibration registers may get corrupted
and the module may get unusable.
ASCII – DELIMITED TEXT (AUTO-SEND MODE ENABLED)
When configured to the auto-send mode, the myPCProbe module transmits to its USB port a line of text containing the
current value of all measurement channels. A new line of text is transmitted after each measurement interval, according
to the module configuration.
Any software with serial communication capabilities can receive these data. When configuring the serial communication
parameters of the software, set the COM port number assigned to the device. The USB port ignores all other serial
communication parameters.
•
Communication Port: Select the COM port number assigned to the myPCProbe.
•
Baud rate: any
•
Number of data bits: any
•
Stop bits: any
•
Parity: any