Mesa Encoder packages defining in the PIN_xx.vhd

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23 Jan 2021 22:37 #196367 by Isleape
Hello, trying to get started with CNC and all the bits and bobs arround it...
I go stuck with the manual encoders for moving the spindes manualy...
Can some one explain the difference between these MESA package encoder types:
(QcountTag),
(MuxedQcountTag),
(MuxedQCountSelTag,

Or at least a recomendation(link) were I can find some more descriptions about Pakages" in general but especialy for these differences ... I did look quite a bit but up to now failed...

I want to use a selectable manual encoder "one for all" - and/or preferable at least two (x and y) axis with two encoders.
From what I found it would be the QcountTag in mode "FALSE" using A & B - but this information was scrached together by me but not found in the manals directley that I had read to far.

I also jumpt through the IDROMconst and found:
--- (QcountTag, x"03", ClockLowTag, x"0n", QcounterAddr&PadT, QCounterNumRegs, x"00", QCounterMPBitMask),
--- IOPortTag & x"01" & QCountTag & x"02", -- I/O 00
--- IOPortTag & x"01" & QCountTag & x"01", -- I/O 01
--- IOPortTag & x"01" & QCountTag & x"03", -- I/O 04

--- (MuxedQcountTag, MQCRev, ClockLowTag, x"0n", MuxedQcounterAddr&PadT, MuxedQCounterNumRegs, X"00", MuxedQCounterMPBitMask),
--- IOPortTag & x"00" & MuxedQCountTag & MuxedQCountQAPin, -- I/O 01
--- IOPortTag & x"00" & MuxedQCountTag & MuxedQCountQBPin, -- I/O 02
--- IOPortTag & x"00" & MuxedQCountTag & MuxedQCountIDXPin, -- I/O 03

--- (MuxedQCountSelTag, x"00", ClockLowTag, x"01", NullAddr&PadT, x"00", x"00", x"00000000"),
--- IOPortTag & x"00" & MuxedQCountSelTag & MuxedQCountSel0Pin, -- I/O 10

- it looks like I would need both for what I want to do - but - as mentiones - I'm not sure.

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23 Jan 2021 23:33 #196372 by PCW
Note that you should only use muxed encoders on specific breakout boards that do encoder multiplexing (7I52,7I52S,7I77,7I85,7I85S,7I89) otherwise just use the standard qcount

For MPGs the INM module may be better depending on the breakout used
(the INM supports 1X mode which is usually preferred for MPGs as you get
exactly one increment per detent
The following user(s) said Thank You: Isleape

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24 Jan 2021 19:32 #196459 by Isleape
Ok - thanks. I have a 7i80HD (and for next project a 7i90HD) with no break out at all. So I would belive I will rebuild, using the INM version.
I also belive to understand that LinuxCNC does the "quasi multiplexing" e.g. tels the SW were to put the encoder - having nothing to do with the FPGA multiplexing...

Were do I find such information? Is the source a place to look first or is there a more elegant place?

As I only have TTL signals so far - and would use opto couples were needed I belive I will not need a break out for my I/O.

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24 Jan 2021 19:47 #196462 by PCW
My multiplex comment was just meant to suggest you should not use muxed encoders
with non-mesa breakouts

Using bare FPGA pins is possible, but beware of ground noise issues
(Step/servo drives and VFDs can generate more than 1V of high frequency voltage
difference between different points in the ground system)

If this noise is present, simple connecting a a bare FPGA pin to frame ground can
destroy an I/O pin by shorting out the lower ESD protection/clamp diode in the FPGA

You can protect against this type failure with a series 220 Ohm or so resistor.

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26 Jan 2021 15:23 #196622 by andypugh

Isleape wrote: Hello, trying to get started with CNC and all the bits and bobs arround it...
...
Can some one explain the difference between these MESA package encoder types:


Maybe you have dived in a bit too deep for just getting started?
Almost no-one needs to compile their own Mesa firmware.

To use one encoder for multiple purposes you would typically do the multiplexing in the LinuxCNC HAL layer. All the jogs and overrides are configured to latch the current encoder counts when they are enabled, and respond only to delta counts.

If you only have one physical encoder you only need one encoder counter.

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04 Feb 2021 12:18 #197645 by Isleape
Yes I agree to have been deepdiving. The lack of understanding my problems dug me even deeper..
Regarding encoders I want a quasi permanent xy encoder... some day.
Until then i will figgure out with one until i get more understanding.
I had difficulties with the large amount of bit files and what they can and do and also in combination with selecting/configuiring it all with the config tool with my level of understanding...... so getting up to speed. and enough other things to so ....thanks

Btw - what referes to the INM module? is this the real name? Is this simply the module that needs to be loaded at start handling the encoders?

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