AHU MODBUS TCP VALUE

[Elmyran]

Hi, I try to connect to Schneider-electric Homelynx and get the airflow from an IVP AHU ventilation unit with a climactix controller.
I need to compare two values in order to control a mixing valve.
The valve opens and closes until the two values are as equal as possible.
The value is to be retrieved from a Holding register with the address 4x0055 and 4x0056.
But unfortunately I do not get any values, it seems that it does not connect or I have typed the wrong code to get the air value correctly.

Code:

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require('luamodbus') if not mb then    mb = luamodbus.tcp()    mb:open('192.168.201.53')    mb:connect() end mb:setdebug(true) openvalue =  grp.getvalue('6/3/1') tfvalue = mb:readinputregisters(54) ffvalue = mb:readinputregisters(55) mb:close() if tfvalue > ffvalue then  if openvalue < 220 then    openvalue = openvalue + 25  end end if ffvalue < ffvalue then  if openvalue > 25 then    openvalue = openvalue - 25  end end grp.write('6/3/1', openvalue)

I would be very grateful if you can help me with this problem
/Tommy

[Erwin van der Zwart]

Hi,

First of all you have not set a port on the Modbus TCP connection:

Code:

1

mb:open('192.168.201.53', 502)

Try also:

Code:

123

tfvalue, ffvalue = mb:readregisters(55, 2) log(tfvalue,ffvalue)

If that does not work try changing 55 to 54

BR,

Erwin

[CHOUAIBOU]

Hi, I try to connect to Schneider-electric Homelynx and get the airflow from an IVP AHU ventilation unit with a climactix controller.
I need to compare two values in order to control a mixing valve.
The valve opens and closes until the two values are as equal as possible.
The value is to be retrieved from a Holding register with the address 4x0055 and 4x0056.
But unfortunately I do not get any values, it seems that it does not connect or I have typed the wrong code to get the air value correctly.

Code:

123456789101112131415161718192021222324

require('luamodbus') if not mb then    mb = luamodbus.tcp()    mb:open('192.168.201.53')    mb:connect() end mb:setdebug(true) openvalue =  grp.getvalue('6/3/1') tfvalue = mb:readinputregisters(54) ffvalue = mb:readinputregisters(55) mb:close() if tfvalue > ffvalue then  if openvalue < 220 then    openvalue = openvalue + 25  end end if ffvalue < ffvalue then  if openvalue > 25 then    openvalue = openvalue - 25  end end grp.write('6/3/1', openvalue)

I would be very grateful if you can help me with this problem
/Tommy

Hi Tommy,
To establish modbus TCP connection between modbus master and modbus slave, you need to specify the port and the slave Id.


B.R,
Chouaibou.

[Erwin van der Zwart]

Hi,

Not 100% sure but i believe slave id is optional by TCP device (without it the default is used).

BR,

Erwin

[admin]

Is it a resident or a scheduled script? If it's resident then it will only work once because you are closing the connection via mb:close(). Setting slave id for TCP is optional by standard (255 is used when not set) but some devices might require it.

Start by logging each step return results:

Code:

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require('luamodbus') local mb = luamodbus.tcp() local res, err = mb:open('192.168.201.53') log('open', res, err) local res, err = mb:connect() log('connect', res, err) local res, err = mb:readinputregisters(54) log('read', res, err) mb:close()

[Elmyran]

Thanks for your help, I got the script to work today. When I contacted AHU, I realized that it was the wrong values I received. There were inputs 95 and 96 that I needed to compare.
Here is the final working code:

Code:

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require('luamodbus') if not mb then    mb = luamodbus.tcp()    mb:open('192.168.201.53', 502)    mb:connect() end openvalue =  grp.getvalue('6/3/1', dt.uint8) tfvalue = mb:readinputregisters(94, dt.uint16) -- 3x0095 Supply air flow ffvalue = mb:readinputregisters(95, dt.uint16) -- 3x0096 Exhaust air flow if tfvalue and ffvalue == 0 then   openvalue = 0 end if tfvalue < ffvalue then   if openvalue < 220 then     openvalue = openvalue + 25   end end if tfvalue > ffvalue then if openvalue > 25 then openvalue = openvalue - 25 end end grp.write('6/3/1', openvalue, dt.int8)

it was as simple as that.