Modbus RTU master with RS485 on PPC30 Error 20292

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1

Hi,
I would like to open Modbus Master by C30 with onboard RS485 interface (IF5).
I’ve got an error 20292 and no communication at all.
Is there any limitation to use RS485 port or 4PPC30.043F-23B to communicate by modbus RTU protocol?
Thank you

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2

Hello,

You can check de error numbers for the DRV_Mbus library here: DRV_Mbus - General Information - Error Numbers

It seems that you have a problem with the available buffer:

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You can that the suggestion for this error is to reduce the workload on your task.

3

Hi,
Thank you for sharring.
DRVmbus has noting to do with DVframe.
And there’s no other task running serial interface.

By the way I’ve run the same code with AS4.12 instead of A6.0 and got no error.
I think it’s something wrong with the AR6.xx

Best Regards

4

Hi,

as I know, DRV_mbus internally uses DVFrame.
So at least it’s plausible and valid, that a DVFrame status error is thrown by DRV_mbus function blocks.

The error code means, that no new send buffer can be allocated.
The frame driver allocates a number of send and receive buffers, and if all send buffers already in use and the next send request is called (which is done automatically inside DRV_mbus), the returned status is 20292.

Sometimes, getting this status could have the cause that the data cannot be sent out to the bus because of physical reasons (wrong / defective connection wiring, missing termination resistors, collisions on the bus because other RS485 devices are sending at the same time, and similar).

5

Yes, I think so.
I confirm no physical issue because the same code is working properly on AS4.12 but this problem is occurred only with AS6.0
I’m not sure is there addition setting on AS6 or there’s something changes on AR6.xx

6

Okay, I’m not aware of any special settings around RS485 configuration or restrictions of using modbus with PPC30.

As I understood, the identical hardware and the same timing + task class settings are used, the only difference is the AR/AS version.
In that case, I only can propose to check if you’re using the latest AS + AR + Firmware versions available, and if yes please contact your local B&R support for further investigation.

Best regards!