lua-libmodbus

Contents

• Functions
• Context Methods
• Constants provided for use

Modules

• libmodbus

Examples

• demo.lua

Source

• lua-libmodbus.c
• demo.lua

Module libmodbus

lua bindings to libmodbus.

Generally, this provides a very thin layer over libmodbus. Instead of passing the context around to all your modbus_xxx functions, you simply call them as member functions on the context returned by the new() functions.

Info:

• License: Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

  The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

  THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

• Author: Karl Palsson 2016-2020

Functions

Context Methods

Constants provided for use

Functions

version () line 80

Returns the runtime linked version of libmodbus as a string. The compile time version is available as a constant VERSION.

Returns:

eg "3.0.6"

See also:

other_constants

new_rtu (device, baud, parity, databits, stopbits) line 100

Create a Modbus/RTU context

Parameters:

• device (required)
• baud rate, defaults to 19200
• parity defaults to EVEN
• databits defaults to 8
• stopbits defaults to 1

Returns:

a modbus context ready for use

new_tcp_pi (host, service) line 164

Create a Modbus/TCP context

Parameters:

• host eg "192.168.1.100" or "modbus.example.org"
• service eg "502" or "mbap"

Returns:

a modbus context ready for use

set_s32 (num) line 199

Write a 32bit (u)int to 2x16bit registers

Parameters:

• num 32bit number

Returns:

1. reg1 upper 16bits
2. reg2 lower 16bits

set_f32 (num) line 214

Write a bit float to 2x16bit registers

Parameters:

• num floating point number

Returns:

1. reg1 upper 16bits of a 32bit float
2. reg2 lower 16bits of a 32bit float

get_s16 (1) line 232

16bit register as number to signed 16bit

Parameters:

• 1 16bit register

Returns:

signed 16bit number

get_s32 (1, 2) line 246

2x16bit registers as number to signed 32 bit

Parameters:

• 1 16bit register
• 2 16bit register

Returns:

32bit number

get_s32le (1, 2) line 262

2x16bit registers as number to signed 32 bit (reverse order)

Parameters:

• 1 16bit register
• 2 16bit register

Returns:

32bit number

get_u32 (1, 2) line 279

2x16bit registers as number to unsigned 32 bit

Parameters:

• 1 16bit register
• 2 16bit register

Returns:

32bit number

get_u32le (1, 2) line 295

2x16bit registers as number to unsigned 32 bit (reversed order)

Parameters:

• 1 16bit register
• 2 16bit register

Returns:

32bit number

get_f32 (1, 2) line 311

2x16bit registers as number to 32 bit float

Parameters:

• 1 16bit register
• 2 16bit register

Returns:

32bit float

get_f32le (1, 2) line 331

2x16bit registers as number to 32 bit float (Reversed order)

Parameters:

• 1 16bit register
• 2 16bit register

Returns:

32bit float

get_s64 (1, 2, 3, 4) line 353

4x16bit registers as number to signed 64 bit

Parameters:

• 1 16bit register
• 2 16bit register
• 3 16bit register
• 4 16bit register

Returns:

64bit number

get_u64 (1, 2, 3, 4) line 376

4x16bit registers as number to unsigned 64 bit

Parameters:

• 1 16bit register
• 2 16bit register
• 3 16bit register
• 4 16bit register

Returns:

64bit number

Context Methods

ctx:connect () line 434

Connect, see modbus_connect()

ctx:close () line 447

Close, see modbus_close()

ctx:set_debug (enable) line 461

Set debug

Parameters:

• enable optional bool, defaults to true

ctx:set_error_recovery (a, b) line 481

Set error recovery, see modbus_set_error_recovery. The arguments will be or'd together.

Parameters:

• a one of error_recovery_constants
• b one of error_recovery_constants

ctx:set_byte_timeout (seconds, microseconds) line 498

See also modbus_set_byte_timeout

Parameters:

• seconds (required)
• microseconds (optional, defaults to 0)

ctx:get_byte_timeout () line 516

Returns:

1. seconds
2. microseconds

ctx:set_response_timeout (seconds, microseconds) line 537

Parameters:

• seconds (required)
• microseconds (optional, defaults to 0)

ctx:get_response_timeout () line 555

Returns:

1. seconds
2. microseconds

ctx:get_socket () line 575

Returns:

the socket number

ctx:set_socket (sock) line 588

Parameters:

• sock integer socket number to set

ctx:rtu_get_serial_mode () line 602

Returns:

rtu_constants the serial mode, either RTU_RS232 or RTU_RS485

ctx:rtu_set_serial_mode (mode) line 618

Sets the mode of a serial port. Remember, this is only required if your kernel is handling rs485 natively. If you are using a USB adapter, you do NOT need this.

Parameters:

• mode The selected serial mode from rtu_constants, either RTU_RS232 or RTU_RS485.

ctx:set_slave (unitid) line 641

Parameters:

• unitid the unit address / slave id to use

ctx:read_input_bits (address, count) line 695

Parameters:

• address
• count

Returns:

an array of results

ctx:read_bits (address, count) line 706

Parameters:

• address
• count

Returns:

an array of results

ctx:read_input_registers (address, count) line 754

Parameters:

• address
• count

Returns:

an array of results

ctx:read_registers (address, count) line 765

Parameters:

• address
• count

Returns:

an array of results

ctx:report_slave_id () line 774

Returns:

a luastring with the raw result (lua strings can contain nulls)

ctx:write_bit (address, value) line 795

Parameters:

• address
• value either a number or a boolean

ctx:write_register (address, value) line 819

Parameters:

• address
• value

ctx:write_bits (address, value) line 836

Parameters:

• address
• value as a lua array table

ctx:write_registers (address, value) line 898

Parameters:

• address
• value as a lua array table, or a sequence of values.

Usage:

either
 ctx:write_registers(0x2000, {1,2,3})
 ctx:write_registers(0x2000, 1, 2, 3)

Constants provided for use

rtu_constants line 1112

RTU Mode Constants

Fields:

• RTU_RS232
• RTU_RS485

See also:

• rtu_get_serial_mode
• rtu_set_serial_mode

error_recovery_constants line 1127

Error Recovery Constants

Fields:

• ERROR_RECOVERY_NONE
• ERROR_RECOVERY_LINK
• ERROR_RECOVERY_PROTOCOL

See also:

set_error_recovery

exception_codes line 1128

Exception codes These are all MODBUS_xxxx upstream in libmodbus.

Fields:

• EXCEPTION_ILLEGAL_FUNCTION
• EXCEPTION_ILLEGAL_DATA_ADDRESS
• EXCEPTION_ILLEGAL_DATA_VALUE
• EXCEPTION_SLAVE_OR_SERVER_FAILURE
• EXCEPTION_ACKNOWLEDGE
• EXCEPTION_SLAVE_OR_SERVER_BUSY
• EXCEPTION_NEGATIVE_ACKNOWLEDGE
• EXCEPTION_MEMORY_PARITY
• EXCEPTION_NOT_DEFINED
• EXCEPTION_GATEWAY_PATH

other_constants line 1156

Other constants

Fields:

• VERSION_STRING the compile time version, see also version
• BROADCAST_ADDRESS used in set_slave
• TCP_SLAVE used in set_slave