Comms with panasonic drive

[Jamie123]

Hello,

I have been asked if its possible to establish communication with an on site PLC (v1210) and a Panasonic drive. Currently in order to change the drive parameters someone has to connect with a PC to make the changes and this has become a bit of a pain. All I need to do is read and write to two parameters on the drive.

I had assumed that the drive had a comms protocol specific to Panasonic and therefore would be unable to establish a connection.

I would be very grateful if someone could have a quick look at the comms chapter of the attached manual and let me know if its possible to establish comms with the PLC.

Thanks in advance

panasonic(vert xis).pdf

[Ausman]

Hi Jamie,

my quick look at that manual says you should be able to change your parameters using 485, which is likely the connection method already in use.  At present they must be disconnecting this to do the programming with the PC.

I think you could certainly develop code for the 1210 to write to the drive.   (Comms start at page 68.)  So you could remotely connect to the 1210 to do so, or have the program set up to let users do whatever is needed.

However, why does this need to happen?  Drive parameters constantly need altering doesn't seem to make sense?

cheers,

Aus 

[Jamie123]

Hi Aus

Thanks for the reply!

The drive operates in sequential mode and moves between 4 set points. Its a chemical dipping application and the speed between points 3 and 4 changes for different components. We can only change this speed by accessing the drive registers via  a PC.

[Joe Tauser]

I've communicated with servo drives before using the Protocol block.  It is certainly possible, and it sounds like you only need to program one command with the speed embedded. 

I've never used it, but it does look like the Protocol Send block has an XOR-8 Checksum calculator built into the Send Variables that can be used to get your BCC value.  I would have to play with this to see if it lines up with the examples in the Panasonic manual.

Joe T.

[Jamie123]

Thanks Joe, I appreciate the help.

[Jamie123]

I have had a bit of a play with this and have fallen at the first hurdle.  I'm trying to replicate the read request command on the top of page 83. This is my first time using Protocol and I haven't a clue what I'm doing.

Could someone please have a look at the screen shot and suggest the reason for the error message?

 

Thanks

[Joe Tauser]

You don't have an actual character in the STX and ETX areas of the dialog.  Those two parts of the dialog are used to insert and append characters outside of your string definitions.  If you double-click the little white box you'll see a list of characters come up that you can choose from.  You can also specify more than one, for example if you always wanted to add CR+LF to the end of every string you send (ETX):

Uncheck them if you're going to embed the STX and ETX characters in the string definition as you have shown.

Joe T.

[Jamie123]

Thanks Joe. I'll have another play this afternoon.

[Jamie123]

After another morning of getting nowhere with this, I have to as for help again.  Could someone please show me what the protocol send and scan blocks should look like to mirror the lines in the picture.

I don't want to continue trouble shooting until I have these blocks correct.

Thanks in advance

 

[Joe Tauser]

I can't seem to get the BCC value to agree with what Panasonic comes up with (0Ch).  The exact method described on page 73 of the manual is rather vague.

I tried adding all the bytes together from STX to ETX as described (02h + ... + 03h) = 212h.  Inverting this (XOR'ing with FF) results in 2EDh, or a checksum character of EDh.

If you've got a contact in Japan for Panasonic please ask for a detailed example of how they arrived at 0Ch for this particular command.

Joe T.

[Ausman]

Hi Jamie, (and Joe)

I'm wondering whether it might be easiest at this stage to put a serial monitor on the PC you connect direct to the drive with.  And then change the parameters and observe the monitored data.  This might point you in a better direction at present.  And if this turns out to be a little unclear, for now I'd be using the  PC to manipulate said data to test out exactly what the drive reacts correctly to.

I have successfully used this freebie, but no guarantees!

http://www.serial-port-monitor.com/Download/free-serial-port-monitor.exe

cheers,

Aus

[Jamie123]

I do have a contact at Panasonic but he is a salesman and doesn't have much technical knowledge. I have sent him an email to clarify the check sum value as I cant work it out either.

I'll have a go at using the serial port monitor.

[Jamie123]

I haven't had a chance to look at this yet, but here is the reply I received from Panasonic.