README
¶
go-modbus
About
This Go package provides Modbus access for client (master) applications to communicate with server (slave) devices, over both TCP/IP and Serial Line/RTU frame protocols.
Note that in modbus terminology, client refers to the master application or device, and the server is the slave waiting to respond to instructions, as shown in this transaction diagram:
This code was originally forked from lubia/modbus and repositioned as a pure client (master) library for use by controller applications.
Enabling the USB Serial Port adapter (RS-232) for RTU Access
Slave devices which have USB ports for RTU access will not work immediately upon hot-plugging into a master computer.
For master devices running linux, the USB serial port adapter must be explicitly activated using the usbserial linux kernel module, as follows:
-
Immediately after plugging in the serial port USB, use dmesg to find the vendor and product ID numbers:
$ sudo dmesg | tail
There should be a line which looks like this:
````
[ 556.572417] usb 3-1: New USB device found, idVendor=04d8, idProduct=000c
-
Use the usbserial linux kernel module to enable it, using the same vendor and product ID numbers from the dmesg output:
$ sudo modprobe usbserial vendor=0x04d8 product=0x000c
3. Confirm that the serial port is attached to a specific tty device file:
```
$ sudo dmesg | tail
There should now be a line like this:
```
[ 2134.866724] usb 3-1: generic converter now attached to ttyUSB0
which means that the serial port is now programmatically accessible via <tt>/dev/ttyUSB0</tt>
## References
- [Modbus Technical Specifications](http://www.modbus.org/specs.php)
- [Modbus Interface Tutorial](http://www.lammertbies.nl/comm/info/modbus.html)
- [Modbus TCP/IP Overview](http://www.rtaautomation.com/modbustcp/)
- [Modbus RTU Protocol Overview](http://www.rtaautomation.com/modbusrtu/)
## Acknowledgements
- [Lubia Yang](http://www.lubia.me) for the [original modbus code](https://github.com/lubia/modbus) in Go
- [l.lefebvre](http://source.perl.free.fr/) for his excellent [modbus client](https://github.com/sourceperl/MBclient) and [server (slave device simulator)](https://github.com/sourceperl/mbserverd) code repositories
- [modbusdriver.com](http://www.modbusdriver.com/) for their free [Diagslave Modbus Slave Simulator](http://www.modbusdriver.com/diagslave.html) tool
- [Mohammad Hafiz (mypapit)](https://plus.google.com/113437861006502895279?rel=author) for his well-written [How to enable USB-Serial Port adapter (RS-232) in Ubuntu Linux](http://blog.mypapit.net/2008/05/how-to-use-usb-serial-port-converter-in-ubuntu.html) blog post
Documentation
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Index ¶
- Constants
- Variables
- func RTURead(serialDevice string, slaveAddress, functionCode byte, ...) ([]byte, error)
- func RTUWrite(serialDevice string, slaveAddress, functionCode byte, ...) ([]byte, error)
- func TCPRead(h string, p, timeOut, transactionID int, functionCode byte, serialBridge bool, ...) ([]byte, error)
- func TCPWrite(h string, p, timeOut, transactionID int, functionCode byte, serialBridge bool, ...) ([]byte, error)
- func ValidFunction(fnCode byte) bool
- func ValidReadFunction(fnCode byte) bool
- func ValidWriteFunction(fnCode byte) bool
- type RTUFrame
- type TCPFrame
Constants ¶
const ( MODBUS_PORT = 502 RTU_FRAME_MAXSIZE = 512 TCP_FRAME_MAXSIZE = 260 FUNCTION_READ_COILS = 0x01 FUNCTION_READ_DISCRETE_INPUTS = 0x02 FUNCTION_READ_HOLDING_REGISTERS = 0x03 FUNCTION_READ_INPUT_REGISTERS = 0x04 FUNCTION_WRITE_SINGLE_COIL = 0x05 FUNCTION_WRITE_SINGLE_REGISTER = 0x06 FUNCTION_WRITE_MULTIPLE_REGISTERS = 0x10 FUNCTION_MODBUS_ENCAPSULATED_INTERFACE = 0x2B EXCEPTION_UNSPECIFIED = 0x00 // catch-all for unspecified modbus errors EXCEPTION_ILLEGAL_FUNCTION = 0x01 EXCEPTION_DATA_ADDRESS = 0x02 EXCEPTION_DATA_VALUE = 0x03 EXCEPTION_SLAVE_DEVICE_FAILURE = 0x04 EXCEPTION_ACKNOWLEDGE = 0x05 EXCEPTION_SLAVE_DEVICE_BUSY = 0x06 EXCEPTION_MEMORY_PARITY_ERROR = 0x08 EXCEPTION_GATEWAY_PATH_UNAVAILABLE = 0x0A EXCEPTION_GATEWAY_TARGET_DEVICE_FAILED_TO_RESPOND = 0x0B )
Variables ¶
var MODBUS_EXCEPTIONS = map[uint16]error{ EXCEPTION_UNSPECIFIED: errors.New("Modbus Error"), EXCEPTION_ILLEGAL_FUNCTION: errors.New("Modbus Error: Illegal Function (0x01)"), EXCEPTION_DATA_ADDRESS: errors.New("Modbus Error: Data Address (0x02)"), EXCEPTION_DATA_VALUE: errors.New("Modbus Error: Data Value (0x03)"), EXCEPTION_SLAVE_DEVICE_FAILURE: errors.New("Modbus Error: Slave Device Failure (0x04)"), EXCEPTION_ACKNOWLEDGE: errors.New("Modbus Error: Acknowledge (0x05)"), EXCEPTION_SLAVE_DEVICE_BUSY: errors.New("Modbus Error: Slave Device Busy (0x06)"), EXCEPTION_MEMORY_PARITY_ERROR: errors.New("Modbus Error: Memory Parity Error (0x08)"), EXCEPTION_GATEWAY_PATH_UNAVAILABLE: errors.New("Modbus Error: Gateway Path Unavailable (0x0A)"), EXCEPTION_GATEWAY_TARGET_DEVICE_FAILED_TO_RESPOND: errors.New("Modbus Error: Gateway Target Device Failed to Respond (0x0B)"), }
Functions ¶
func RTURead ¶
func RTURead(serialDevice string, slaveAddress, functionCode byte, startRegister, numRegisters uint16, debug bool) ([]byte, error)
RTURead performs the given modbus Read function over RTU to the given serialDevice, using the given frame data
func RTUWrite ¶
func RTUWrite(serialDevice string, slaveAddress, functionCode byte, startRegister, numRegisters uint16, data []byte, debug bool) ([]byte, error)
RTUWrite performs the given modbus Write function over RTU to the given serialDevice, using the given frame data
func TCPRead ¶
func TCPRead(h string, p, timeOut, transactionID int, functionCode byte, serialBridge bool, slaveAddress byte, data []byte, debug bool) ([]byte, error)
TCPRead performs the given modbus Read function over TCP to the given host/port combination, using the given frame data
func TCPWrite ¶
func TCPWrite(h string, p, timeOut, transactionID int, functionCode byte, serialBridge bool, slaveAddress byte, data []byte, debug bool) ([]byte, error)
TCPWrite performs the given modbus Write function over TCP to the given host/port combination, using the given frame data
func ValidFunction ¶
ValidFunction returns a boolean, depending on whether or not the given code corresponds to a valid modbus function code, read, write, or interface
func ValidReadFunction ¶
ValidReadFunction returns a boolean, depending on whether or not the given code corresponds to a valid modbus read function code
func ValidWriteFunction ¶
ValidWriteFunction returns a boolean, depending on whether or not the given code corresponds to a valid modbus write function code
Types ¶
type RTUFrame ¶
type RTUFrame struct {
DebugTrace bool
SlaveAddress byte
FunctionCode byte
StartRegister uint16
NumberOfRegisters uint16
Data []byte
}
func (*RTUFrame) GenerateRTUFrame ¶
GenerateRTUFrame is a method corresponding to a RTUFrame object which returns a byte array representing the associated serial line/RTU application data unit (ADU)
func (*RTUFrame) TransmitAndReceive ¶
func (frame *RTUFrame) TransmitAndReceive(fd io.ReadWriteCloser) ([]byte, error)
TransmitAndReceive is a method corresponding to an RTUFrame object which generates the corresponding ADU, transmits it to the modbus server (slave device) specified by the given file pointer (serial port), and returns a byte array of th e slave device's reply, and error (if any)
type TCPFrame ¶
type TCPFrame struct {
TimeoutInMilliseconds int
DebugTrace bool
TransactionID int
FunctionCode byte
EthernetToSerialBridge bool
SlaveAddress byte
Data []byte
}
func (*TCPFrame) GenerateTCPFrame ¶
GenerateTCPFrame is a method corresponding to a TCPFrame object which returns a byte array representing the associated TCP/IP application data unit (ADU)
func (*TCPFrame) TransmitAndReceive ¶
TransmitAndReceive is a method corresponding to a TCPFrame object which generates the corresponding ADU, transmits it to the modbus server (slave device) specified by the TCP address+port, and returns a byte array of the slave device's reply, and error (if any)
Source Files
Directories