Absolute Encoder Questions / SSI via 5i25
- juwi
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23 Oct 2012 20:32 #25705
by juwi
Replied by juwi on topic Re:Absolute Encoder Questions / SSI via 5i25
PCW wrote:
Hereby asking - Lascar says 3 weeks delivery time for the 7i74
Thank you!
Regarding the rest of your mail, that makes more sense than a grey pin and a binary pin per SSI. Thanks for your suggestions!
best regards,
julian
compiling emc......
[...]
If you want me to make a config with the free SSERIAL port on a 7I77 used for SSI just ask
Hereby asking - Lascar says 3 weeks delivery time for the 7i74
Thank you!
Regarding the rest of your mail, that makes more sense than a grey pin and a binary pin per SSI. Thanks for your suggestions!
best regards,
julian
compiling emc......
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23 Oct 2012 21:02 #25707
by PCW
Replied by PCW on topic Re:Absolute Encoder Questions / SSI via 5i25
freeby.mesanet.com/7i77_ssi_7i74.bit
Has just one SSI interface on the 7I77s RS422/485 expansion port
Note that this expansion port is a RS-485 capable interface so has a /XMIT
enable on GPIO-0 you will need to set low by making GPIO-0 an output and setp-ing it low
in your hal file
Has just one SSI interface on the 7I77s RS422/485 expansion port
Note that this expansion port is a RS-485 capable interface so has a /XMIT
enable on GPIO-0 you will need to set low by making GPIO-0 an output and setp-ing it low
in your hal file
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23 Oct 2012 21:26 #25711
by andypugh
Replied by andypugh on topic Re:Absolute Encoder Questions / SSI via 5i25
PCW wrote:
Why would you use Gray code on a serial protocol?
GrayCode (bit) binary if false, graycode if true
Why would you use Gray code on a serial protocol?
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23 Oct 2012 21:29 #25712
by juwi
Replied by juwi on topic Re:Absolute Encoder Questions / SSI via 5i25
andypugh wrote:
SSI is either grey or binary coded...
Ist SSI specific.
Best regards,
Julian
PCW wrote:
GrayCode (bit) binary if false, graycode if true
Why would you use Gray code on a serial protocol?
SSI is either grey or binary coded...
Ist SSI specific.
Best regards,
Julian
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23 Oct 2012 21:32 #25713
by andypugh
Replied by andypugh on topic Re:Absolute Encoder Questions / SSI via 5i25
juwi wrote:
Yes, I understand that. I am wondering why.[SSI is either grey or binary coded...
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23 Oct 2012 21:36 #25714
by juwi
Replied by juwi on topic Re:Absolute Encoder Questions / SSI via 5i25
Probably historical reasons... Grey Code has been used on rotary encoders...
SSI is just a shift register, easy to integrate. So you stay where you are with what you have and extend it?
Beste regards,
Julian
SSI is just a shift register, easy to integrate. So you stay where you are with what you have and extend it?
Beste regards,
Julian
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23 Oct 2012 21:38 #25715
by PCW
Replied by PCW on topic Re:Absolute Encoder Questions / SSI via 5i25
Historically absolute encoders (brushed or optical) were parallel interfaced
so always used gray codes to prevent large errors at transitions
probably most early SSI encoders used simple logic circuits to
serialize the parallel gray code data. Converting to binary at the
encoder is a newer innovation.
so always used gray codes to prevent large errors at transitions
probably most early SSI encoders used simple logic circuits to
serialize the parallel gray code data. Converting to binary at the
encoder is a newer innovation.
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23 Oct 2012 21:42 #25716
by juwi
Replied by juwi on topic Re:Absolute Encoder Questions / SSI via 5i25
I am typing on my mobile and have been faster 
Good night
Good night
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08 Nov 2012 00:18 #26347
by juwi
Replied by juwi on topic Absolute Encoder Questions / SSI via 5i25
Ok, after looking a bit deeper into this, I have some additional Things to do...
Questions:
- What Signals are really needed? velocity, position, ?
- Velocity can be calculated as in encoder.c?
best regards,
Julian
Questions:
- What Signals are really needed? velocity, position, ?
- Velocity can be calculated as in encoder.c?
best regards,
Julian
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08 Nov 2012 01:04 #26348
by PCW
Replied by PCW on topic Absolute Encoder Questions / SSI via 5i25
With SSI you are stuck with calculating velocity as delta-position/delta-time
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