7i97T - Custom bitfile request (High-speed 200MHz Encoder for Linear Motors)

  • Gotrune
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23 Sep 2026 18:03 #349814 by Gotrune
Hi PCW,
I am currently retrofitting a machine with a Mesa 7i97T and JAT Ecovario drives controlling permanent magnet linear motors.
My problem is that my high-resolution optical scales (1µm/step which are passed-through directly from the drives, with no hardware division possible) are dropping pulses during high acceleration, even with "filter 0" set in my HAL file. The minimum edge separation of the raw encoder signals is too tight and violates the standard MuxedQCount clock limit.
Could you please compile a custom bitfile for the 7i97T where the encoder counting module clock is bumped to 200MHz (or the maximum possible frequency for this FPGA) to handle these extremely fast edges?
I only need the standard 7i97T I/O pinout, just with the fastest possible encoder sampling.
Thank you in advance!

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23 Sep 2026 18:29 #349815 by PCW
I would try setting:

hm2_7i97.0.encoder.muxed-sample-frequency

to say 20 MHz

(you can probably go higher by futzing with the muxed- skew parameter)
 

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  • Gotrune
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23 Sep 2026 19:16 #349816 by Gotrune
Hi PCW,

Thank you so much for the incredibly fast reply!

I will add setp hm2_7i97.0.encoder.muxed-sample-frequency 20000000 to my HAL file right away and test the machine.

Just to make sure I fully understand the limits of the hardware: what are the acceptable or maximum values for this parameter with the standard 7i97T bitfile? For example, does it need to be a specific integer divisor of the base clock? Also, at what frequency would I typically need to start adjusting the muxed-skew parameter you mentioned?

Thanks again for your time and excellent support!

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  • tuxcnc
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23 Sep 2026 19:33 #349817 by tuxcnc

[code][code]my high-resolution optical scales (...) are dropping pulses during high acceleration
[/code][/code]

Acceleration has nothing to do with it.
Only maximum speed matters.
From the resolution and speed you will calculate the pulse frequency.

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