Does the 7i92-7i76-7i74 firmware support SSI ?

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18 Dec 2017 06:01 - 18 Dec 2017 06:17 #103270 by Cornflakes
Hi

Does the 7i92-7i76-7i74 firmware support SSI ?
I need to connect 6 absolute encoders.

Or I need special version?

How many ports support SSI in this configuration ?

Thanks!
Dmitry
Last edit: 18 Dec 2017 06:17 by Cornflakes.

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18 Dec 2017 15:10 #103289 by PCW
There's no standard firmware for this but it should be easy to cobble together.
As far as SSI channels go, I'll have to see how many fit.
I'll try to get to this today or tomorrow sometime.

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18 Dec 2017 17:17 #103298 by PCW
freeby.mesanet.com/7i92_7i76_7i74_ssid.bit

8 SSI channels fit without a problem
( I was probably thinking about BISS which is substantially larger than SSI )
The following user(s) said Thank You: Cornflakes

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19 Dec 2017 04:44 #103330 by Cornflakes
Replied by Cornflakes on topic Does the 7i92-7i76-7i74 firmware support SSI ?
PCW,

Thank you for support!

Dmitry

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10 Jan 2018 21:07 - 10 Jan 2018 21:10 #104252 by Nick
Hi, PCW

It's hard to find firmwares with ssi support. They are not included into Support software packs and can be only found at some rare posts at the forum (with secret links to freeby.mesanet.com/something_ssi.bit :) ).
Are there any for 5i25+7i77 (+7i74) and 7i92+7i77 (+7i74)?
Most of times I'll need 3-6 ssi encoders but sometimesonly 1 will be enough.
Last edit: 10 Jan 2018 21:10 by Nick.

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11 Jan 2018 02:04 - 11 Jan 2018 02:04 #104269 by PCW
Its not a common config but I can make them, I'll try and get to this sometime this week.
Last edit: 11 Jan 2018 02:04 by PCW.

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20 Jan 2018 22:27 #104755 by PCW

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22 Jan 2018 06:01 #104830 by Nick
Thank you very much! I'll gona try it this week.

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31 Jan 2018 15:50 #105233 by Cornflakes
Replied by Cornflakes on topic Does the 7i92-7i76-7i74 firmware support SSI ?
Hi, PCW!

Can SSI channels work in Slave mode, acting as a „listener“ to the existing data communication between encoder and servo amplifier?
It's a big problem to connect absolute encoder of servo to amplifier and to 7i74 simultaneously

Maybe it needs change only two bytes of code :)

Thanks!

Sorry for my English :)

With hope
Dmitry

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31 Jan 2018 16:11 #105235 by PCW
It should be possible to do this but its awkward for a number of reasons:

1. isolation/noise: The drives encoder interface is often a much noisier environment than the drives host interface
its not really intended that these signals be tapped at this place

2. You would need 2 differential receiver interfaces without termination (not a problem but awkward wiring wise with a 7I44/7I74)

3. The servo drives encoder interface is asynchronous to LinuxCNC's sampling leading to beats and problems with
velocity estimation ( without added hardware to timestamp the servos reads )

4. Drives with absolute encoders usually have a way to read this absolute position

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