SwiftLibModbus is a modern Swift wrapper around the libmodbus C library, providing a convenient, type-safe interface for communicating with Modbus devices using Swift Concurrency features.
SwiftLibModbus leverages Swift Concurrency (async/await) to provide a clean, efficient API for Modbus RTU and TCP communication. The library is designed for ease of use while maintaining the full power of the underlying libmodbus implementation.
Key features:
- Swift Concurrency support (async/await)
- Support for Modbus RTU (serial) and Modbus TCP connections
- Type-safe register/coil reading and writing
- Automatic connection management
- Swift actor model for thread safety
- Easy handling of endianness
- Swift 6.1+
- iOS 18+ or macOS 15+
Add SwiftLibModbus as a dependency to your Package.swift file:
dependencies: [
.package(url: "https://github.com/jollyjinx/SwiftLibModbus.git", from: "2.0.0")
]Then add the dependency to your target:
.target(
name: "YourTarget",
dependencies: ["SwiftLibModbus"]
)import SwiftLibModbus
// Connect to a Modbus TCP device
let device = try ModbusDevice(
networkAddress: "192.168.1.100",
port: 502,
deviceAddress: 1
)
// Read holding registers
let holdingRegisters: [UInt16] = try await device.readHoldingRegisters(
from: 0x1000,
count: 16
)
// Write to holding registers
try await device.writeRegisters(
to: 0x1000,
arrayToWrite: [UInt16(1), UInt16(2), UInt16(3)]
)import SwiftLibModbus
// Connect to a Modbus RTU (serial) device
let device = try ModbusDevice(
device: "/dev/tty.usbserial-42340",
slaveid: 1,
baudRate: 9600,
dataBits: 8,
parity: .none,
stopBits: 1
)
// Read coils
let coils = try await device.readInputCoilsFrom(
startAddress: 0x00,
count: 10
)
// Read input registers
let inputRegisters: [UInt16] = try await device.readInputRegisters(
from: 0x00,
count: 10
)The library supports reading various fixed-width integer types as well as floating point values:
// Read as 16-bit unsigned integers
let uint16Values: [UInt16] = try await device.readRegisters(
from: 0x1000,
count: 10,
type: .holding
)
// Read as 32-bit unsigned integers
let uint32Values: [UInt32] = try await device.readRegisters(
from: 0x1000,
count: 5,
type: .holding
)
// Read as IEEE-754 floating point
let floatValues: [Float] = try await device.readRegisters(
from: 0x1000,
count: 5,
type: .holding
)
// Read as ASCII string
let asciiString = try await device.readASCIIString(
from: 0x1000,
count: 10,
type: .holding
)You can specify endianness when reading or writing registers:
// Read registers with little endian byte order
let values: [UInt32] = try await device.readRegisters(
from: 0x1000,
count: 10,
type: .holding,
endianness: .littleEndian
)The library has built-in management for connections:
// Connect with auto-reconnect after 1 hour and disconnect when idle for 30 seconds
let device = try ModbusDevice(
networkAddress: "example.com",
port: 502,
deviceAddress: 1,
autoReconnectAfter: 3600.0, // 1 hour in seconds
disconnectWhenIdleAfter: 30.0 // 30 seconds
)For more complete examples, see:
- swift-modbus-2-mqtt-bridge - A bridge converting Modbus to MQTT
SwiftLibModbus Version 2 has been developed by @jollyjinx for Swift Concurrency Support and is available under the MIT license. The underlying libmodbus C library is licensed under LGPL.