Raspberry Pi 4 with Mesa 7c81
- andypugh
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You will only need the quadrature counters if you plan to close the loop in LinuxCNC rather than in the stepper drivers.From what I have seen on the fourms, this is a more unusual setup, and I will need to make and flash a custom bitfile to my board.
My understanding is that I will need PWM + 3StepGens + 3QCounts.
I guess you want the PWM for spindle control?
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- maurice
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Has anyone experimented with closing the loop in the driver, and then also reading the same encoder's position into LinuxCNC? Or is this the usual way of doing it?
Yes, PWM Would be for spindle control.
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- PCW
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converts them to single ended. I would suggest a 7I85S which has 4
single ended or differential encoder inputs and 4 buffered 5V step/dir
outputs.
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- andypugh
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Has anyone experimented with closing the loop in the driver, and then also reading the same encoder's position into LinuxCNC? Or is this the usual way of doing it?
It would be simpler to just trust the driver to send an alarm signal if the position is lost.
Though, I admit, if I was doing it I would want to get the position back to LinuxCNC too.
Mesa make an encoder signal splitter, but you might not need that, especially if the drive has a mirrored encoder output (as some do)
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- maurice
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I think I will just get stuff working by closing the loop through the driver for now. That would only require the Stepgens, which one of the included bitfiles has enough of.
If I wanted to get the encoder signal to both LinuxCNC and the driver (no mirror), what advantages would the signal splitter have over simply splicing the wires?
For the 7I85S, I assume that I would need to flash a special bitfile to my 7C81? I don't see any 7I85S bitfile in the downloads.
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- andypugh
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No advantage if splicing the wires works. But it might not.If I wanted to get the encoder signal to both LinuxCNC and the driver (no mirror), what advantages would the signal splitter have over simply splicing the wires?
That's one for PCW but I found a VHDL file "PIN_7C80_7I85D_54" in the source. I am not sure what the "D" signifies though.For the 7I85S, I assume that I would need to flash a special bitfile to my 7C81? I don't see any 7I85S bitfile in the downloads.
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- tommylight
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I am not sure what the "D" signifies though.
I would venture a guess at DPLL feature ...
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- PCW
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- maurice
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- boyzo
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Thank you for help
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