So I have made significant progress on the sigma5abs encoder front. I have
designed a manchester transiever in vhdl and integrated it into hostmot2
firmware as well as linuxcnc. I am close to having a fully functioning
driver. However there are a few mysteries remaining. This is the first
absolute encoder that I have had my hands on so I'm hoping others will know
more.
The encoders are 24 bit with 21 bits per turn so they track 8 turns worth
of counts. Part of the protocol has a 3 bit value that is a sort of turn
counter. It seems to only change if a complete turn is made. For example if
you rotate the encoder until the turn count changes, then reverse, the turn
value will not change until at least an entire rotation occurs. So
depending on the direction and partial reversing, each turn counter value
can occur at 3 different transition points.
This chart shows a mapping between the 24 bit count and possible "turn"
values.
2097152 7 0 1
4194304 0 1 2
6291456 1 2 3
8388608 2 3 4
10485760 3 4 5
12582912 4 5 6
14680064 5 6 7
16777216 (0) 6 7 0
What is the technical term for this style of counter? I can see how it
could be used to determine the rollover point of the counter. What possible
ways should this be used?
Thanks,
Curt
On Mon, Mar 30, 2020, 5:13 PM Curtis Dutton <curtd...@gmail.com> wrote:
> Ok thanks. Once I get things working and know the register layout of the
> finished module I will get some advice as to a final proper address
> location.
>
> On Mon, Mar 30, 2020 at 5:01 PM Peter C. Wallace <p...@mesanet.com> wrote:
>
>> On Mon, 30 Mar 2020, Curtis Dutton wrote:
>>
>> > Date: Mon, 30 Mar 2020 16:33:13 -0400
>> > From: Curtis Dutton <curtd...@gmail.com>
>> > Reply-To: EMC developers <emc-developers@lists.sourceforge.net>
>> > To: EMC developers <emc-developers@lists.sourceforge.net>
>> > Subject: [Emc-developers] Mesa Sigma5ABS module
>> >
>> > Hi all,
>> >
>> > I'm working out the design for the Yaskawa Sigma V absolute encoders.
>> >
>> > Within hostmot2-firmware,
>> >
>> > I've been studying the code and I'm not sure of the exact interface
>> between
>> > the mesa pci cards and linuxcnc.
>> >
>> > It seems that the pci card is mapping registers into memory and that
>> each
>> > module is reserving a register address so that the hostmot2 driver knows
>> > where to look for them to control them.
>> >
>> >
>> > In IDROMConst.vhd, I'm looking for register address space to use. But
>> I'm
>> > getting the feeling that it is all used up. Perhaps that is the reason
>> that
>> > pkuart chose to use the same address's as the uart module.
>> >
>> > The DPLLFreqLowAddr comments "note overlaps translate RAM" and "will
>> fix in
>> > the greate re-alignment"....
>> >
>> > Does anyone know what the great re-alignment will be?
>> >
>> > Can anyone shed some light on the addressing scheme used with the mesa
>> > cards. Any other overview of how it works would be useful too.
>>
>> At one time there was only 32K of useable address space because the EPP
>> interfaced cards used the MSB of the address as an address autoinc flag.
>> Since
>> EPP interfaced cards are basically legacy devices at this point, newer
>> hm2
>> modules use addresses > 0x7FFF and currently B000,C000,D000,E000,F000 are
>> all
>> free.
>>
>> At some point, complile time allocation of module addresses might make
>> sense,
>> but that's a fairly large change so I think I'll wait until I run out of
>> address
>> space until I do that.
>>
>> Note, there's no harm in overlap as long as you dont expect to use the
>> overlapping modules in the same configuration
>>
>>
>> >
>> >
>> > Thanks,
>> > Curt
>> >
>> > _______________________________________________
>> > Emc-developers mailing list
>> > Emc-developers@lists.sourceforge.net
>> > https://lists.sourceforge.net/lists/listinfo/emc-developers
>> >
>>
>> Peter Wallace
>> Mesa Electronics
>>
>>
>>
>> _______________________________________________
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>> Emc-developers@lists.sourceforge.net
>> https://lists.sourceforge.net/lists/listinfo/emc-developers
>>
>
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