用lua语言实现modubus协议组装

以下是用Lua语言实现Modbus协议组装的示例代码：

-- Modbus Function Codes
local MB_FUNC_READ_COILS = 0x01
local MB_FUNC_READ_DISCRETE_INPUTS = 0x02
local MB_FUNC_READ_HOLDING_REGISTERS = 0x03
local MB_FUNC_READ_INPUT_REGISTERS = 0x04
local MB_FUNC_WRITE_SINGLE_COIL = 0x05
local MB_FUNC_WRITE_SINGLE_REGISTER = 0x06
local MB_FUNC_WRITE_MULTIPLE_COILS = 0x0F
local MB_FUNC_WRITE_MULTIPLE_REGISTERS = 0x10

-- Modbus Exception Codes
local MB_EX_ILLEGAL_FUNCTION = 0x01
local MB_EX_ILLEGAL_DATA_ADDRESS = 0x02
local MB_EX_ILLEGAL_DATA_VALUE = 0x03
local MB_EX_SLAVE_DEVICE_FAILURE = 0x04

-- Function to pack data into a Modbus frame
local function pack_modbus_frame(slave, func, data)
    local frame = string.pack(">BB", slave, func) .. data
    local crc = 0xFFFF
    for i = 1, #frame do
        crc = bit.bxor(crc, string.byte(frame, i))
        for j = 1, 8 do
            if bit.band(crc, 0x0001) == 0x0001 then
                crc = bit.bxor(bit.rshift(crc, 1), 0xA001)
            else
                crc = bit.rshift(crc, 1)
            end
        end
    end
    frame = frame .. string.pack("<H", crc)
    return frame
end

-- Function to read coils from a Modbus slave
function modbus_read_coils(slave, address, count)
    local data = string.pack(">HH", address, count)
    local frame = pack_modbus_frame(slave, MB_FUNC_READ_COILS, data)
    -- send frame to Modbus slave and get response
    -- ...
    -- parse response and return coil values
    -- ...
end

-- Function to read holding registers from a Modbus slave
function modbus_read_holding_registers(slave, address, count)
    local data = string.pack(">HH", address, count)
    local frame = pack_modbus_frame(slave, MB_FUNC_READ_HOLDING_REGISTERS, data)
    -- send frame to Modbus slave and get response
    -- ...
    -- parse response and return register values
    -- ...
end

-- Function to write a single coil to a Modbus slave
function modbus_write_single_coil(slave, address, value)
    local data = string.pack(">HH", address, value)
    local frame = pack_modbus_frame(slave, MB_FUNC_WRITE_SINGLE_COIL, data)
    -- send frame to Modbus slave and get response
    -- ...
    -- parse response and return status
    -- ...
end

-- Function to write a single holding register to a Modbus slave
function modbus_write_single_register(slave, address, value)
    local data = string.pack(">HH", address, value)
    local frame = pack_modbus_frame(slave, MB_FUNC_WRITE_SINGLE_REGISTER, data)
    -- send frame to Modbus slave and get response
    -- ...
    -- parse response and return status
    -- ...
end

-- Function to write multiple coils to a Modbus slave
function modbus_write_multiple_coils(slave, address, count, values)
    local byte_count = math.ceil(count / 8)
    local data = string.pack(">HHB", address, count, byte_count) .. values
    local frame = pack_modbus_frame(slave, MB_FUNC_WRITE_MULTIPLE_COILS, data)
    -- send frame to Modbus slave and get response
    -- ...
    -- parse response and return status
    -- ...
end

-- Function to write multiple holding registers to a Modbus slave
function modbus_write_multiple_registers(slave, address, count, values)
    local byte_count = count * 2
    local data = string.pack(">HHB", address, count, byte_count) .. values
    local frame = pack_modbus_frame(slave, MB_FUNC_WRITE_MULTIPLE_REGISTERS, data)
    -- send frame to Modbus slave and get response
    -- ...
    -- parse response and return status
    -- ...
end

这些函数可以与串口通信或TCP/IP连接一起使用，以与Modbus从设备进行通信。请注意，此代码示例仅实现了一些常见的Modbus功能码，并且仅提供了基础的错误处理和CRC计算。对于实际应用程序，您可能需要根据您的特定需求进行修改和扩展。