SSI ABS Encoder

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06 May 2021 14:27 #208118 by annhandt09
Replied by annhandt09 on topic SSI ABS Encoder

PCW wrote: What does hm2_7i80.0.ssi.00.zencoder.rawcounts
show?


it show from 0-4096
But when I restart linux cnc, the values (3072 to 4096 ) is negative numbers from -1024 ->-1

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06 May 2021 14:32 #208121 by andypugh
Replied by andypugh on topic SSI ABS Encoder

annhandt09 wrote: The values return from 0x0000000->0x0000ffff for 0->4096


This is starting to look like it's my fault, then.

However I am fairly sure that the encoder wrapping logic works properly, as it is used extensively by things like the smart-serial MPG counters.

Is the returned position continuous at least? If it is then the conventional axis home offsets will mask the issue.

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06 May 2021 14:34 #208122 by annhandt09
Replied by annhandt09 on topic SSI ABS Encoder
can you see the video?



thank you very much

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06 May 2021 14:39 #208123 by andypugh
Replied by andypugh on topic SSI ABS Encoder

annhandt09 wrote: But when I restart linux cnc, the values (3072 to 4096 ) is negative numbers from -1024 ->-1


I think what is happening is that the initial change from the initialisation value of zero and the first real data is looking like an encoder wrap. But if the M flag is set then it shouldn't even be running the wrap code.

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06 May 2021 14:46 #208125 by annhandt09
Replied by annhandt09 on topic SSI ABS Encoder

andypugh wrote:

annhandt09 wrote: But when I restart linux cnc, the values (3072 to 4096 ) is negative numbers from -1024 ->-1


I think what is happening is that the initial change from the initialisation value of zero and the first real data is looking like an encoder wrap. But if the M flag is set then it shouldn't even be running the wrap code.


i only reboot my LinuxCNC. The power of the encoder is still ON

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06 May 2021 14:52 #208126 by andypugh
Replied by andypugh on topic SSI ABS Encoder
And I think I see the problem.

github.com/LinuxCNC/linuxcnc/blob/master...2/abs_encoder.c#L258

The check will fail for a "me" as the check list does not contain "m".
Which means that you can't use the "%12me" specifier (that would raise an error) and "%12em" will simply not parse the m.

Are you running LinuxCNC 2.8 or are you running master from buildbot? I can get a fix in to the master .debs pretty quickly.

If you are building from source then that would be even better, as you can test the fix before I make it...

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06 May 2021 15:00 #208128 by andypugh
Replied by andypugh on topic SSI ABS Encoder

annhandt09 wrote: i only reboot my LinuxCNC. The power of the encoder is still ON


Yes, but when you reboot LinuxCNC the internal "last position" is zero, and the wrap-detection kicks in.

This isn't typically wrong as-such, though it really should be returning -2048 for 2048 and 2047 for 2047

I think that you should see the same behaviour if the encoder is also powered down?

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06 May 2021 15:16 #208130 by annhandt09
Replied by annhandt09 on topic SSI ABS Encoder

andypugh wrote:

annhandt09 wrote: i only reboot my LinuxCNC. The power of the encoder is still ON


Yes, but when you reboot LinuxCNC the internal "last position" is zero, and the wrap-detection kicks in.

This isn't typically wrong as-such, though it really should be returning -2048 for 2048 and 2047 for 2047

I think that you should see the same behaviour if the encoder is also powered down?


i tried to turn off the power of encoder when the linuxcnc work. When i turn on the power then the data is correct.

I am using the brand s_kins ( github.com/LinuxCNC/linuxcnc/tree/dgarr/s_kins )

Sorry for my English. I am learning English.

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06 May 2021 16:21 #208132 by andypugh
Replied by andypugh on topic SSI ABS Encoder
If you are building from source, can you try editing abs_encoder.c, so that line 258 is
else if (strchr("bBuUsSeEfFpPgGhHlLmM", *format)){

And then see if "%12me" fixes the problem?

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06 May 2021 16:40 - 06 May 2021 16:42 #208133 by annhandt09
Replied by annhandt09 on topic SSI ABS Encoder

andypugh wrote: If you are building from source, can you try editing abs_encoder.c, so that line 258 is

else if (strchr("bBuUsSeEfFpPgGhHlLmM", *format)){

And then see if "%12me" fixes the problem?


i tried this. The encoder data returned : 0->2047 - 2047 -2046 ...->-1 for 0->4096 datas
Is it correct?
Last edit: 06 May 2021 16:42 by annhandt09.

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