Modbus; Operating With The Modules - Libelium Waspmote Technical Manual

19.5. Modbus

The Modbus is a software library that can be operated physically on the RS-485 and RS-232 modules. Thus, Modbus is a software
layer which provides with interesting services.
Technical details:
• Protocol: Modbus
• Data area: Up to 255 bytes per job
• Interface: Layer 7 of the ISO-OSI reference model
• Connector: DB9 (RS-485 / RS-232 modules)
Number of possible connections: up to 32 in multi point systems
•
Frame format: RTU
•
Applications:
• Multiple master-slave applications
• Sensors and Instruments
• Industrial Networking
• Building and infrastructure
• Transportation and energy applications

19.6. Operating with the modules

The functions implemented in the API allow to configure the modules and send information in a simple way, calling functions
such as:
{
W485.send("Data from analog1 input: ");
W485.send(analog1);
}
{
W232.send("Data from analog1 input: ");
W232.send(analog1);
}
{
// Read the last message received
CAN.getMessage(&CAN.messageRx);
// Print in the serial monitor the received message
CAN.printMessage(&CAN.messageRx);
}
Related API libraries:
• Wasp485.h, Wasp485.cpp.
• Wasp232.h, Wasp232.cpp.
• WaspCAN.h, WaspCAN.cpp.
• ModbusMaster485.h, ModbusMaster485.cpp, ModbusSlave485.h, ModbusSlave485.cpp.
• ModbusMaster232.h, ModbusMaster232.cpp, ModbusSlave232.h, ModbusSlave232.cpp.
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Industrial Protocols
Figure: RS-485 module
v6.3