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SSI encoder

  • nhanpham
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17 Jan 2023 14:37 #262238 by nhanpham
SSI encoder was created by nhanpham
hi all,I have an ABS encoder, CAX60.My config in linuxcnc

loadrt hm2_eth board_ip="10.10.10.10" config=" num_encoders=0  num_stepgens=6  ssi_chan_0=ENC_ZH%24eENC_SIGN_Z%1b 

# set speed
setp hm2_7i80.0.dpll.02.timer-us -300

setp hm2_7i80.0.ssi.00.frequency-khz 125  
setp hm2_7i80.0.ssi.00.timer-number 2
setp hm2_7i80.0.ssi.00.ENC_ZH.counts-per-rev 4096
setp hm2_7i80.0.ssi.00.ENC_ZH.scale -32.25

However, I received a random encode value. 
At home position:
When I open the linuxcnc and turn on power, I get the 0 value of encoder. 
But sometimes i turn on linuxcn at this position and i get 250 value of encoder.

can you hel me check my config is correctly?

thank you so much
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17 Jan 2023 14:46 #262239 by andypugh
Replied by andypugh on topic SSI encoder
Is the problem just the startup value, or does it not give useful output either?
ie, is it _always_ random, or just at startup?

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17 Jan 2023 14:58 #262240 by nhanpham
Replied by nhanpham on topic SSI encoder
It is simply random when starting up. 
thank you so much

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17 Jan 2023 15:12 #262243 by PCW
Replied by PCW on topic SSI encoder
I would first try all 4 combinations of polarity

(all 4 combinations of swapped CLK+ and CLK- and swapped DATA+and DATA-)

Also its hard to tell from the awful data sheet, but it seems to be a Gray
coded encoder so your format string may not be correct.

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17 Jan 2023 16:03 #262245 by nhanpham
Replied by nhanpham on topic SSI encoder
Could you possibly give me a format for this encoder? i will test it tomorrow.

Thank you for your help.

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17 Jan 2023 16:08 #262246 by andypugh
Replied by andypugh on topic SSI encoder
Apart from the startup value, does the position otherwise work, ie increases smoothly without jumps as it is turned?

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17 Jan 2023 16:19 - 17 Jan 2023 16:31 #262249 by PCW
Replied by PCW on topic SSI encoder
Also the documentation mentions a parity bit... Not sure if this is present or not

Replacing the "e" with a "g" in the format string will convert the encoders Gray code to binary
Last edit: 17 Jan 2023 16:31 by PCW.

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17 Jan 2023 16:26 #262251 by nhanpham
Replied by nhanpham on topic SSI encoder
maybe. my encoder is a binary code.

Yes, this error just happens at startup. After it worked perfectly from the start pos, which it read during startup

thank you

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17 Jan 2023 17:33 #262255 by PCW
Replied by PCW on topic SSI encoder
So it only works properly after the encoder position changed?

A SSI encoder should always have a valid output

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18 Jan 2023 01:07 #262295 by annhan
Replied by annhan on topic SSI encoder
Yes, it has an error in that it gets a different encoder value when I turn on the encoder power.After reading this value, the LinuxCNC worked normally and produced no errors. 
thank you

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