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 83

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 103

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 168

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 204

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 221

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 239

16bit register as number to signed 16bit

Parameters:

• 1 16bit register

Returns:

signed 16bit number

get_s32 (1, 2) line 253

2x16bit registers as number to signed 32 bit

Parameters:

• 1 16bit register
• 2 16bit register

Returns:

32bit number

get_s32le (1, 2) line 269

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 286

2x16bit registers as number to unsigned 32 bit

Parameters:

• 1 16bit register
• 2 16bit register

Returns:

32bit number

get_u32le (1, 2) line 302

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 318

2x16bit registers as number to 32 bit float

Parameters:

• 1 16bit register
• 2 16bit register

Returns:

32bit float

get_f32le (1, 2) line 338

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 360

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 383

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 441

Connect, see modbus_connect()

ctx:close () line 454

Close, see modbus_close()

ctx:set_debug (enable) line 468

Set debug

Parameters:

• enable optional bool, defaults to true

ctx:set_error_recovery (a, b) line 488

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 505

See also modbus_set_byte_timeout

Parameters:

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

ctx:get_byte_timeout () line 523

Returns:

1. seconds
2. microseconds

ctx:set_response_timeout (seconds, microseconds) line 544

Parameters:

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

ctx:get_response_timeout () line 562

Returns:

1. seconds
2. microseconds

ctx:get_socket () line 582

Returns:

the socket number

ctx:set_socket (sock) line 595

Parameters:

• sock integer socket number to set

ctx:rtu_get_serial_mode () line 609

Returns:

rtu_constants the serial mode, either RTU_RS232 or RTU_RS485

ctx:rtu_set_serial_mode (mode) line 628

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:rtu_get_rts () line 645

Returns:

rtu_rts_constants the RTS handling mode, up/down/none

ctx:rtu_set_rts (mode) line 662

Sets the RTS handling of a serial port.

Parameters:

• mode The selected RTS handling mode from rtu_rts_constants, up/down/none.

ctx:rtu_get_rts_delay () line 679

Returns:

usecs

ctx:rtu_set_rts_delay (usecs) line 696

Sets the RTS delay of a serial port.

Parameters:

• usecs

ctx:get_header_length () line 714

Returns the header length of the transport

Returns:

the length in bytes

ctx:set_slave (unitid) line 727

Parameters:

• unitid the unit address / slave id to use

ctx:read_input_bits (address, count) line 781

Parameters:

• address
• count

Returns:

an array of results

ctx:read_bits (address, count) line 792

Parameters:

• address
• count

Returns:

an array of results

ctx:read_input_registers (address, count) line 840

Parameters:

• address
• count

Returns:

an array of results

ctx:read_registers (address, count) line 851

Parameters:

• address
• count

Returns:

an array of results

ctx:report_slave_id () line 860

Returns:

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

ctx:write_bit (address, value) line 881

Parameters:

• address
• value either a number or a boolean

ctx:write_register (address, value) line 905

Parameters:

• address
• value

ctx:write_bits (address, value) line 922

Parameters:

• address
• value as a lua array table

ctx:write_registers (address, value) line 984

Parameters:

• address base address to write to
• 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)

ctx:tcp_pi_listen (conns) line 1095

Parameters:

• conns max connections to listen to, defaults to 1

Returns:

the new socket number or normal error

ctx:tcp_pi_accept (sock) line 1117

Parameters:

• sock the socket we're accepting on

Returns:

the new socket we've accepted or normal error

ctx:receive () line 1141

Receives a request from a remote. WARNING this might not be complete, documented that it exists

Returns:

1. the length of the data
2. the data received

ctx:reply_exception (initial, exc) line 1183

Reply to a request with an Exception.

Parameters:

• initial the initial request to build into an exception
• exc the exception code to use from exception_codes

Returns:

the new socket number or normal error

Constants provided for use

rtu_constants line 1230

RTU Mode Constants

Fields:

• RTU_RS232
• RTU_RS485

See also:

• rtu_get_serial_mode
• rtu_set_serial_mode

rtu_rts_constants line 1238

RTU RTS Consants

Fields:

• RTU_RTS_NONE
• RTU_RTS_UP
• RTU_RTS_DOWN

See also:

• rtu_set_rts
• rtu_get_rts

error_recovery_constants line 1253

Error Recovery Constants

Fields:

• ERROR_RECOVERY_NONE
• ERROR_RECOVERY_LINK
• ERROR_RECOVERY_PROTOCOL

See also:

set_error_recovery

exception_codes line 1254

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 1285

Other constants

Fields:

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