Fanuc RJ3iB conversion with servo amp

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10 Mar 2021 14:36 #201649 by ExcessiveO
has anyone converted a rj3ib controller? I am looking for a way to reuse the servo amplifier and link it to linux cnc. However it is driven by an optical connection that runs at 25Mhz and I have no idea what protocol it is. Has anyone had any success reusing one of these amplifiers?

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10 Mar 2021 23:41 #201758 by andypugh
I don't know of anyone who has managed to derive the optically-connected drives. I would imagine that the optical connection is less of a problem than the unknown protocol.

Have you searched the web to see if anyone has connected them to anything at all other than the original controller?

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11 Mar 2021 00:02 #201761 by PCW
I wonder if dm17ry who makes the Yaskawa mechatrolink interface has looked at this?

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11 Mar 2021 00:06 #201763 by ExcessiveO
I was able to scope the signal which was how I found it was 25Mhz. I looked but couldn't find much of anything on the protocol. I'm going to hook up a logic analyzer and see if I can make any progress decoding it.

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11 Mar 2021 00:23 - 11 Mar 2021 00:24 #201768 by andypugh
That should work, but there is likely to be a checksum and working out how to generate those can be hard.
Last edit: 11 Mar 2021 00:24 by andypugh.

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11 Mar 2021 00:26 #201769 by PCW
There's a very nice tool called CRC RevEng that can help with CRC's

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11 Mar 2021 12:48 #201808 by dm17ry

I wonder if dm17ry who makes the Yaskawa mechatrolink interface has looked at this?

no, i haven't so far. found a machine with fanuc control, but never managed to get there with a logging hardware.

ArkaumIndustries, if you can record some logs with a logic analyzer - i will jump in to reverse engineering. 25MHz sounds right, i have seen 50Mbps FSSB data rate mentioned in some fanuc paper. mitsubishi uses 8b/10b encoding over the fiber, expect something similar here...

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12 Mar 2021 23:20 #202031 by ExcessiveO
I just hooked up an analyzer and got a first sample of data. I believe ch1 is transmitting from the computer and ch0 is back from the amp. It also looks like ch0 picks up some noise sometimes so I'll have try again sometime to maybe get it a bit better. I honestly have no idea where to start with this, ill probably try to clean up the data into more exact bits but that will probably take a while.

Attached is the raw data of the very beginning of transfer:

File Attachment:

File Name: data1short.zip
File Size:30 KB
Attachments:

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