FBL2360T 13Bit SSI Absolute encoder support

4 months 2 days ago #29535303 by geism5
Hi there
In the Controllers Datasheet is written:
The controller issues a differential clock signal and expects a 12-bit differential data signal from the encoder. When two motors are used, these signals must be connected to both sensors. Serial data from each  sensor is captured on separate input pins.

I read the topic SBL2360 13Bit SSI Absolute encoder support so it seems to be that 13bit encoders sould also work with my motor controller FBL2360T its that right?

I'm using a 13Bit RM44SC Encoder from RLS (see attached Datasheet)
I tried to use this encoder to control the motor in Closed Loop Speed but this seems not to work correctly.
So I measured the CLK signal sendt from the controller and Data signal sendt from the encoder (see attached image)


Why the controller sends 16 clk signals, I expected only 13
what i have to do, that only 13bits are read?

Do you have any step by step procedure to put in use a SSI encoder on this controller?

Thanks for your response!
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3 months 2 weeks ago #29535307 by Athanasios
Hi geism5,
many of our clients are using the RLS encoders without problem
make sure that you have wired correctly.
Rotate the motor by hand and see if the SSI counter values are changing. To see this go to run tab and choose the SSI counter 1 or SSI coutner 2

What sensor are you using for the comuutation?
Try to run in open loop. 
If it is the same SSI encoder then the problem is at the closed loop settings. 

 

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3 months 2 weeks ago #29535309 by geism5
Hi Athanasios,

Thanks for your reply.
Meanwhile it seems to work with my encoder.
I'm using a 13Bit RM44SC Encoder from RLS.

But I'm still interestet in why the controller is sending 16 CLK-cycles for a presetted resolution of 13bit.
What exactly changes if I change the "SPI/SSI Sensor Resolution" from 4096 to 8192?

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3 months 2 weeks ago #29535310 by airnamicsZoran
By SSI spec data is sent MSB first. From observation I guess the implementaton is as follows: if you set 4096, the first 12 bits are read, and if you set 8192, the first 13 bits are read, but in either case 16 clocks are generated. This way up to 16 bits can be read without changing clock parameters. I have a 12-bit encoder connected:
 
 
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