Modbus master or slave, RTU or TCP, without writing a driver.
Poll meters, PLCs, and sensors, or make your device readable by SCADA systems. Modbus in AppBlocks is a set of ready-made blocks, so reading a register takes a block, not a protocol stack.
The Modbus you actually use in the field.
Master and slave
Poll other devices as a master, or answer requests as a slave.
RTU and TCP
Modbus RTU over RS-485 or RS-232, and Modbus TCP on port 502.
Standard function codes
Read and write coils and registers with function codes 01–06, 15, and 16.
Registers linked to variables
In slave mode, registers are linked to your app’s variables automatically.
Event blocks
React to responses, timeouts, and incoming requests with dedicated event blocks.
Bridge to IT systems
Forward readings over MQTT, HTTP, or to AppBlocks Cloud in the same flow.
Three flows that cover most Modbus projects.
Poll meters and PLCs as a master
Send a Modbus Request on a timer, then handle the answer in On Modbus Response. If a device stops answering, On Modbus Timeout tells you so you can log it or raise an alarm.
- Modbus Request, On Modbus Response, On Modbus Timeout
- Scale raw register values with math blocks
- RTU over serial, or TCP over the network
Expose your device to SCADA as a slave
Turn your device into a Modbus slave and its variables become registers that PLCs and SCADA systems can read and write. On Modbus Received fires whenever a master writes, so your flow can react.
- temperature, humidity, and pump_on linked to registers
- RTU on RS-485, or TCP on port 502
Bridge Modbus to the cloud
Legacy equipment speaks Modbus; your dashboards and back end don’t. Read the registers, convert the values, and forward them over MQTT, HTTP, or AppBlocks Cloud, all in one flow.
AppBlocks CloudQuestions, answered.
Does AppBlocks support Modbus RTU and Modbus TCP?
Yes, both. Modbus RTU runs over RS-485 or RS-232, and Modbus TCP runs over the network on port 502.
Can a device be a Modbus master and a slave?
AppBlocks supports both roles. As a master it polls other devices; as a slave it exposes its variables as registers.
Which function codes are supported?
Function codes 01 to 06, 15, and 16, which cover reading and writing coils, discrete inputs, and holding and input registers.
Can I convert Modbus to MQTT?
Yes. Read registers with Modbus blocks and publish the values with the MQTT Publish block in the same flow. MQTT in AppBlocks.
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