Hello hope some one can help me as a newbee in modbus i have (3) heatpumps (for cascade) but i do not get acces to the heat pump data.

I have set up a dell laptop with a usb to RS 485 interface.

I dont know what i do wrong.
I get back two messages:
1-Modbus error exception respons from slave device
2-Checksum erro in responce message

in the return is see: 40321 return value --27076

i have attached several pictures of information i have.

(sorry for bad EN)

In case of anny question, please ask.

Marienk

 

Do you have all 3 heat pumps connected to your USB to RS-485 interface? If so, they must all be configured for different slave addresses, otherwise they will all try to respond at the same time.

Since you are getting valid data sometimes, this could be a timing issue. In ModScan's Protocol Selections options in the Connection Details window, try increasing your Slave Response Timeout (try 1000) and Delay Between Polls (try 500). If the heat pumps have an option for a response delay, try increasing that to something like 50 to 100ms.

 

No only one heatpump

 

Do you have all 3 heat pumps connected to your USB to RS-485 interface? If so, they must all be configured for different slave addresses, otherwise they will all try to respond at the same time.

Since you are getting valid data sometimes, this could be a timing issue. In ModScan's Protocol Selections options in the Connection Details window, try increasing your Slave Response Timeout (try 1000) and Delay Between Polls (try 500). If the heat pumps have an option for a response delay, try increasing that to something like 50 to 100ms.

Does it has any means that the replay is a negative value? -27076 ?

 

The value itself is irrelevant to the communications. The fact that ModScan shows any value besides 0 indicates it received at least one valid response from the heat pump.

The reason ModScan is showing a negative value is because of the display options you've selected. If, for example, you were to select Unsigned Integer instead of Integer, ModScan would show a large, positive number (38,460 to be exact).

Have you tried my previous suggestions regarding the timing?

If you're still having problems, you may need to double-check your wiring and possibly try a different USB to RS-485 adapter.

 

The value itself is irrelevant to the communications. The fact that ModScan shows any value besides 0 indicates it received at least one valid response from the heat pump.

The reason ModScan is showing a negative value is because of the display options you've selected. If, for example, you were to select Unsigned Integer instead of Integer, ModScan would show a large, positive number (38,460 to be exact).

Have you tried my previous suggestions regarding the timing?

If you're still having problems, you may need to double-check your wiring and possibly try a different USB to RS-485 adapter.

First of all I realy appreciate your feed back, its verry help full!!

Regarding your previous suggestion, unfortunately I could not check these settings, because the heat pumps are on a industrial roofbuilding. And the building is closing at 4,30 pm.
Tomorrow morning at first I'll check your suggestions.

Then regarding the USB to RS485 adapter, I don't know the exact type, but I fount here that is seems a reliable model.

I will update this thread with the in use USB to RS485 adapter.

I'll update tomorrow morning

 

Do you have all 3 heat pumps connected to your USB to RS-485 interface? If so, they must all be configured for different slave addresses, otherwise they will all try to respond at the same time.

Since you are getting valid data sometimes, this could be a timing issue. In ModScan's Protocol Selections options in the Connection Details window, try increasing your Slave Response Timeout (try 1000) and Delay Between Polls (try 500). If the heat pumps have an option for a response delay, try increasing that to something like 50 to 100ms.

Hello JSchultze,

i have tested your propsed setting but that, reated a time out error.

in the modscan connetion setting menu the max vaulue is 10. so i could not make thesettings as you propsed 1000and 500.

if i changed to 9 and 5 then i get a time out error

 

Hello JSchultze,

i have tested your propsed setting but that, reated a time out error.

in the modscan connetion setting menu the max vaulue is 10. so i could not make thesettings as you propsed 1000and 500.

if i changed to 9 and 5 then i get a time out error

also what i noticeted that the led txd and rxd blinking very fast. i dont know if that has any meaning

 

Hello JSchultze,

i have tested your propsed setting but that, reated a time out error.

in the modscan connetion setting menu the max vaulue is 10. so i could not make thesettings as you propsed 1000and 500.

if i changed to 9 and 5 then i get a time out error

What settings are you actually changing? The settings I was describing can be found in ModScan by clicking Connection->Connect, then in the Connection Details window, click Protocol Selections. Here is what it looks like:


I'm also concerned that you may have changed other settings in ModScan or in the Advanced settings for your USB to RS-485 adapter that are actually what is causing the issues you're seeing.

also what i noticeted that the led txd and rxd blinking very fast. i dont know if that has any meaning

What LEDs? On your USB to RS-485 adapter?

Rapidly blinking TX and RX LEDs typically mean communications is working. However, this heavily depends on the timing options you have configured (Slave Response Timeout and Delay Between Polls) as well as the timing of the slave as to how quickly it responds to requests.

 

It seems i had a wrong connector on the printing board

What settings are you actually changing? The settings I was describing can be found in ModScan by clicking Connection->Connect, then in the Connection Details window, click Protocol Selections. Here is what it looks like:
View attachment 3420

I'm also concerned that you may have changed other settings in ModScan or in the Advanced settings for your USB to RS-485 adapter that are actually what is causing the issues you're seeing.


What LEDs? On your USB to RS-485 adapter?

Rapidly blinking TX and RX LEDs typically mean communications is working. However, this heavily depends on the timing options you have configured (Slave Response Timeout and Delay Between Polls) as well as the timing of the slave as to how quickly it responds to requests.

>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
This thread is solved!

causing the problem was factor scheme drawing has a mistake, we have used the wrong connector on the printing board.

We have used the correct connector and getting the modbus data on our screen.

Solution was use the right connector on the main board.

Manny thanks to jschulze he has guid me in the right direction.

>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>