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+--- Thread: Modbus function code 23 (#17) (/showthread.php?tid=5949)
Modbus function code 23 (#17) - alb-smith - 27.03.2025
Does LM support the Modbus function code 23 with profiles or with a script (luamodbus)?
Thanks.
RE: Modbus function code 23 (#17) - admin - 27.03.2025
See this: https://forum.logicmachine.net/showthread.php?tid=1225&pid=13244#pid13244
Are you sure that function 23 is needed? Usually you can do writing and reading separately.
RE: Modbus function code 23 (#17) - alb-smith - 27.03.2025
Thanks for the answer.
User manual of this device seems to require FC 23 as you can see in the picture.
It's a Modbus interface for Mastervolt Battery charger (https://www.mastervolt.it/prodotti/masterbus-interfaces/masterbus-modbus-interface/)
RE: Modbus function code 23 (#17) - alb-smith - 28.03.2025
When trying to implement communication with this device I always get the error "Bad file descriptor".
This LM uses both Modbus RTU ports with a different configuration.
Code:
require('luamodbus')
buffer = {}
function logger(c)
table.insert(buffer, c)
end
local mb2 = luamodbus.rtu()
mb2:open('/dev/rs485-2', 19200, 'E', 8, 1, 'H')
mb2:connect()
mb2:setslave(1)
mb2:setdebug(logger)
values,err=mb2:writereadregisters(0,6,12,0x0A,0x1AE0F,0x0,0x1)
log(table.concat(buffer))
mb2:close()This is the RTU port configuration:
RE: Modbus function code 23 (#17) - admin - 28.03.2025
RS must be uppercase in the port name.
RE: Modbus function code 23 (#17) - alb-smith - 29.03.2025
I partially solved it using the send() function sending a string to the device.
In debug I can see the response which is complete and correct but the mb:receive() function returns a timeout error.
Code:
require('luamodbus')
function hexToString(hex)
-- Remove any spaces or invalid characters
hex = hex:gsub("([^0-9a-fA-F])", "")
-- Convert each pair of hex digits into a character
local str = ""
for i = 1, #hex, 2 do
local byte = hex:sub(i, i + 1)
str = str .. string.char(tonumber(byte, 16))
end
return str
end
buffer = {}
function logger(c)
table.insert(buffer, c)
end
local mb2 = luamodbus.rtu()
mb2:open('/dev/RS485-2', 19200, 'E', 8, 1, 'H')
mb2:connect()
mb2:setslave(1)
mb2:setreceivetimeout(1.0)
mb2:setresponsetimeout(1.0)
mb2:setdebug(logger)
local variable_number = '11' -- in hexadecimal
hex_decoded = hexToString("011700000006000000060c0a01ae0f000000" .. variable_number .. "00000000")
-- Sending
variabile,err_s=mb2:send(hex_decoded)
-- Response
local response,err = mb2:receive()
-- Log the sending operation
if variabile then
log("Is send successful?: ")
log(variabile)
else
log("Sending error: "..err_s)
end
-- Log the response
if response then
log("Response from device: " .. table.concat(response, ", "))
else
log("Response error: ".. err_r)
end
log(table.concat(buffer))
mb2:close()Logs report:
Response error: Operation timed out
Debug:
* string: [01][17][00][00][00][06][00][00][00][06][0C][0A][01][AE][0F][00][00][00][11][00][00][00][00][91][AF]
Waiting for a indication...
<01><17><0C><0A><01><AE><0F><00><00><00><11><00><00><00><42><C1><35>ERROR Operation timed out: select
The response captured by debug is complete and correct.
I tried to change setreceivetimeout() and setresponsetimeout() with no effects.
RE: Modbus function code 23 (#17) - admin - 31.03.2025
You can't use receive for master operation. The equivalent of your raw string using writereadregisters is this:
Code:
mb:writereadregisters(0, 0x0A01, 0xAE0F, 0, 0x0011, 0, 0, 0, 6)