Sending a message to the CANbus with a Schneider M241 PLC

Hello everyone!

I have a Schneider M241 as master of a CAN network with several encoders and whatnot, everything is working fairly well. Now, recently I had to add a new device to the network, an IMET M880 Zeus2 waist belt transmitter, which I did and is working OK. Except for one thing: I cannot write to its display (it's an optional feature to include a display, but my client requested one).

See, IMET provided me with an EDS file, so all I did in my SoMachine project was install the device using said file through the Device Repository, add it to my CANOpen bus, and voilÃ*, I had all my variables automatically mapped. All I did was put a name on them and add them to my logic.

This worked wonders for all the Tx-PDO's, i.e. reading which joystick I am moving and which way, etc. But apparently, for the Rx-PDO's (a.k.a writing to the display) it does not. I follow the manual's instructions (see image no. 1) and nothing happens.

Now, I used a CAN Interface for PC and the Maintenance Tool software by IFM to connect my laptop to the CANbus. I started monitoring it, and came to realize that not one message was sent to the COB-ID 264H, which explained why nothing was showing up in the display. Then, I used said software to manually write the HELLO word, and it worked! (See image no. 2)

Obviously, then, I am doing something wrong in the PLC part. From what I understand, all I have to do is move HEX values to the corresponding USINT mapped variables, nothing fancy, but I must be missing something. In particular, I'm doing:


I also tried changing the Transmission Type in the PDO configuration from SoMachine, but none of the available options worked and I really don't know what else to try.

I apologize if this is too dumb, and I hope anyone of you know the answer. Thank you!

Have not used SoMachine but in some other systems, I have had to adjust the inhibit time of PDOs if they defaulted to something that would try to send data continuously. This keeps the PDO from being sent (or attempting to be sent) more frequently than the inhibit time.

ndzied1 said:

Have not used SoMachine but in some other systems, I have had to adjust the inhibit time of PDOs if they defaulted to something that would try to send data continuously. This keeps the PDO from being sent (or attempting to be sent) more frequently than the inhibit time.

Click to expand...

Hello Norman, thanks for replying. Unfortunately, SoMachine does not let me adjust the inhibit time of this particular PDO (see image no. 3), or any RxPDOs for that matter. I can, however, adjust for TxPDOs. I can only assume that it was disabled by the manufacturer via the EDS file, but that's only my guess.

Hello again, I continued my investigation and discovered that, while connected online to the PLC, you can read and write SDOs from SoMachine using the Status tab under a CANOpen device.

Now, I set some values into the corresponding variables and then read the appropriate Object Dictionary using the functionality mentioned above. This way, I was able to see that the variables 1 and 2 (Start_Pos and Valid_Chars), had in fact taken the value I assigned to them. However, variables 3 to 8 (i.e. Char_1 to Char_6) remained with the value of 32: the ASCII value for the space character, which is why nothing appears on the display. (See images no. 5 and 6 to check what I am describing)

Another thing I tried is to write manually into this objects, bypassing the PDO, but that didn't work as the CANbus returned an error code of 0x6010002, which apparently stands for "attempting to write to a read-only object". I checked the EDS, and these show as write-only, not read-only, so this is also very odd.

Conclusion: I am more or less at the same place I was yesterday.