[etherlab-dev] "Failed to read number of assigned PDOs for SM2" error occurs.

Christoph Schroeder christoph.schroeder at helmholtz-berlin.de
Wed May 31 11:44:26 CEST 2017


I am not 100% sure but I will write down some conjectures what could cause the problem. I think the critical part is this:

        <Mailbox DataLinkLayer="true">
          <CoE CompleteAccess="false" PdoUpload="true" SdoInfo="true"/>

This is the description of PdoUpload:
Device has dynamic process data, i.e. PDO configuration
and PDO assignment is uploaded from the device and
SyncManager lengths are set according to the calculated
PDO length.
0: PDO description taken from ESI and SyncManager
length calculated based on the same
1: PDO description uploaded from the slave’s object
dictionary and SyncManager length calculated based on the

>From what I understand there is a static and a dynamic way to manage process data. The static way means the PDO informations resp. the SyncManager length are stored in the EEPROM which is retrieved by the EtherCAT master during initialization. The PDO informations are not mandatory but the SyncManager length is.

Complex slaves, resp. slaves with attached microcontroller / FPGA etc. that support mailbox communication, support a dynamic way where the PDO informations are retrieved via the mailbox CoE protocol. The SyncManager length is then calculated based on these informations. This of course has to be supported by the microcontroller / FPGA or in your case the OMRON-NJ501 PLC or rather by it's software / configuration. Unfortunately I can't tell you how to exactly do this as we never used CoE. We also use the LAN9252 as complex slave with a FPGA but with a custom configuration and only VoE mailbox protocoll.

One other guess: the ESI file tells me that CoE is not completely supported but some features that use CoE are. Maybe this confuses the EtherCAT master? This would also explain why "EtherCAT ERROR 0-0: Received mailbox protocol 0x08 as response." occurs which means only FoE is set as supported mailbox protocol. Setting the bit in the EEPROM might be of help here, but could lead to other errors.

Best regards,

On 05/31/2017 10:09 AM, 권태영 wrote:

I am testing the EtherLab with the MicroChip EVB-LAN9252-ADD-ON board.
The EVB-LAN9252-ADD-ON board is connected to ODROID-C1 and is used as an EtherCAT slave as SOES(SPI communication).
Kernel version is using version 3.10.

I tested the ported SOES with OMRON-NJ501-1500 PLC and Sysmac Studio. (Attached file: 1.png)

I have compiled EtherLab to do the same EtherCAT Master operation.(etherlab-bundle-2.1)

I tried to control it with the ethercat command.
However, the following error message appears.

EtherCAT WARNING 0-0: Received mailbox protocol 0x08 as response.
EtherCAT ERROR 0-0: Failed to read number of assigned PDOs for SM2.
EtherCAT WARNING 0-0: Received mailbox protocol 0x08 as response.
EtherCAT ERROR 0-0: Failed to read number of assigned PDOs for SM3.
EtherCAT 0: Bus scanning completed in 90 ms.
EtherCAT 0: Using slave 0 as DC reference clock.
EtherCAT 0: Slave states on main device: PREOP.
EtherCAT ERROR 0-0: Received mailbox protocol 0x08 as response.

On the EVB-LAN9252-ADD-ON board, only the Run LED is blinking.(PEROP)

How can I tell if I can solve this problem?
Why does this error occur?
I am EtherCAT Newbi.... :(

The attached log.txt is all the commands and logs I have run.
The attached kty.xml file is the ESI file currently being used by the EtherCAT Slave.
The attached 2.jpg is the current status of my board.


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