That is really good news, thanks to both of you Lukasz and Chris.
Not only that we got a technical solution but that we manage it time after time
to come to joint solutions in the project (which is way more important than
finding technical solutions IMHO).
Hope to be able to contribute more, soon : )
Julian
Am 06.05.20, 01:33 schrieb "Łukasz Dywicki" <l...@code-house.org>:
Last Saturday I promised to Chris I will confirm the case and I just did.
As suggested - I rearranged field order in State type and made a test to
proof myself, that it works:
https://github.com/apache/plc4x/commit/3010fdd15524410dfd55746562ed44bcee0fe80f
I've closed related issue (PLC4X-193) and created pull requests. Changes
in mspec are not needed for that case.
It took quite long, but we managed to find solution.
Cheers,
Łukasz
On 01.05.2020 10:53, Christofer Dutz wrote:
> Hi folks,
>
> so Lukasz just sent me a little pcap file with some AMS packets in there
and my assumption was correct:
>
> for example in the byte-stream I can see the "flags" being 0x0400 ...
However wireshark read this as unsigned short LE and therefore re-aranged the
bytes:
> StateFlags: 0x0004
> .... .... .... ...0 = RESPONSE: Not set
> .... .... .... ..0. = NO RETURN: Not set
> .... .... .... .1.. = ADS COMMAND: Set
> .... .... .... 0... = SYSTEM COMMAND: Not set
> .... .... ...0 .... = HIGH PRIORITY COMMAND: Not set
> .... .... ..0. .... = TIMESTAMP ADDED: Not set
> .... .... .0.. .... = UDP COMMAND: Not set
> .... .... 0... .... = INIT COMMAND: Not set
> 0... .... .... .... = BROADCAST: Not set
>
> So in above example only one field is true: "ADS COMMAND" ... so if I
decode 0x0400 to binary that’s: 00000100 00000000
>
> So this exactly fits my proposed mspec definition of:
>
> [type 'State'
> [simple bit 'initCommand' ]
> [simple bit 'updCommand' ]
> [simple bit 'timestampAdded' ]
> [simple bit 'highPriorityCommand' ]
> [simple bit 'systemCommand' ]
> [simple bit 'adsCommand' ]
> [simple bit 'noReturn' ]
> [simple bit 'response' ]
> [simple bit 'broadcast' ]
> [reserved int 7 '0x0' ]
> ]
>
> So I strongly object introducing any special endianness "feature" for
this (in this case) ...
> we might encounter something where we need it, but for this we don't.
>
> Chris
>
>
>
> Am 30.04.20, 23:02 schrieb "Christofer Dutz" <christofer.d...@c-ware.de>:
>
> Hi Lukasz,
>
> I wasn't suggesting to look how WireShark decodes things. Cause I
would assume that they read a short in little endian and then (on the
rearranged bytes) apply some bit checks.
>
> I was more suggesting that you look into the bytes Wireshark shows
you and to check their exact position.
>
> When implementing drivers, I used the Mac's Calculator tool quite
often to see the bits for a given byte value.
>
> In your example I can't see any need for endianness at all ... it's
all just bits and one empty block which forms a full byte together with the
first bit.
> As this block doesn't cross any byte boundaries I can't see any
problems with this.
>
> Assuming I understand what you are implying with
>
> [type little endian 'State'
> [simple bit 'broadcast' ]
> [reserved int 7 '0x0' ]
> [simple bit 'initCommand' ]
> [simple bit 'updCommand' ]
> [simple bit 'timestampAdded' ]
> [simple bit 'highPriorityCommand' ]
> [simple bit 'systemCommand' ]
> [simple bit 'adsCommand' ]
> [simple bit 'noReturn' ]
> [simple bit 'response' ]
> ]
>
> Then it should be equal to:
>
> [type 'State'
> [simple bit 'initCommand' ]
> [simple bit 'updCommand' ]
> [simple bit 'timestampAdded' ]
> [simple bit 'highPriorityCommand' ]
> [simple bit 'systemCommand' ]
> [simple bit 'adsCommand' ]
> [simple bit 'noReturn' ]
> [simple bit 'response' ]
> [simple bit 'broadcast' ]
> [reserved int 7 '0x0' ]
> ]
>
> Which also seems to be the exact order how the bits go over the wire
... I mean ... it doesn't make any sense to put the 7 empty bits in the middle.
>
> Chris
>
>
> Am 30.04.20, 22:42 schrieb "Łukasz Dywicki" <l...@code-house.org>:
>
> Hey Chris and others,
> I let this topic to dust and freeze a bit, however I would like
to lift
> it up again. Since the 0.7 release is now in discussion and ADS
is not
> ported yet I believe it is reasonable to validate this problem.
>
> As you suggested I've checked wireshark sources to see how they
parse
> state fragment of AMS header. While I can not read C properly and
was
> unable to locate actual reading logic, I do see they care about
endianness:
>
https://github.com/wireshark/wireshark/blob/5cf3fd03f1538b37704d83b6c38b8223f9036108/plugins/epan/ethercat/packet-ams.c#L429
>
> Their frame traversal goes in following order:
> - response
> - no return
> - ads cmd
> - system cmd
> - high priority
> - timestamp add
> - udp
> - init cmd
> - broadcast
>
> When I've tried to model mspec with respect to little endian
order, I
> end up with following field order:
> - init cmd
> - udp
> - timestamp add
> - high priority
> - system cmd
> - ads cmd
> - no return
> - response
> - [reserved]
> - broadcast
>
> I haven't seen ADS protocol book, my main source of information is
> infosys which is rather short in this area. I doubt if they would
> describe fields in above order.
>
> My initial attempts were similar to what you said - to read the
value
> and then shift bytes. With your feedback I started to look for
better
> ways to solve it. With my last attempt I solved the problem by
> re-adjusting fields during code generation, so they appear in a
valid
> byte order. Beside additional flag at the mspec there is a need
for this
> helper:
>
build-utils/protocol-base-mspec/src/main/java/org/apache/plc4x/plugins/codegenerator/language/mspec/model/definitions/DefaultComplexTypeDefinition.java
>
> In above commit the State declaration in the mspec looks like
this:
> [type little endian 'State'
> [simple bit 'broadcast' ]
> [reserved int 7 '0x0' ]
> [simple bit 'initCommand' ]
> [simple bit 'updCommand' ]
> [simple bit 'timestampAdded' ]
> [simple bit 'highPriorityCommand' ]
> [simple bit 'systemCommand' ]
> [simple bit 'adsCommand' ]
> [simple bit 'noReturn' ]
> [simple bit 'response' ]
> ]
>
> Maybe it is not in line with wireshark, but it is consistent and:
> 1) requires minor change in code generator
> 2) does not involve additional processing of data
> 3) mspec is still easy to write
> 4) type declaration is in line with wireshark output when reading
from
> the left and not from the top. ;-)
> 5) it can be adjusted to be 100% consistent with wireshark by
changing
> helper logic. ;-)
>
> Best regards,
> Łukasz
>
>
> On 14.04.2020 21:25, Christofer Dutz wrote:
> > Hi Lukasz,
> >
> > I see it differently.
> >
> > If you say something is LE/BE then it should be consistent.
> >
> > I for my part like it if the mspec is consistent with what I
see in WireShark. Otherwise you would always have to do a sort of 2 step
parsing:
> >
> > "Read 4 bytes in BE and then on the rearranged byte sequence
take the first 3 bits and call them X and the next bit after that Y and so on."
> >
> > In this case you would also have to know how large the chunk is
to read in order to know how to decode it's content.
> > Having a historically partitioned set of two 16 bit bit-fields
would look completely different to a 32 bit bit-field.
> >
> > I don't like adding this extra level, even if it's probably the
way protocols were implemented when lacking the ability to write individual
bits.
> > I guess the usual process was to read a BE short (2 bytes) and
to the resulting unsigned short value apply different logical or operations to
get the information.
> > In PLC4X we can simply read any number of bits and don't have
to twist our minds in which chunks I have to read things first.
> >
> > So I think the way you are proposing is probably the wider used
version due to legacy restrictions, but also the more complicated way.
> >
> > So I would like to keep it simple, even if the developer will
have to do a little more brain-work.
> >
> > I mean all we are doing in this project is going the extra mile
so others don't have to ... at least the ones contributing are doing that.
> >
> > What do the others say to this? (Ideally ones that have already
used mspec or ones that understand the problem)
> >
> > Chris
> >
> >
> > Am 14.04.20, 15:46 schrieb "Łukasz Dywicki"
<l...@code-house.org>:
> >
> > Hey Chris,
> > Sorry for wrongly addressed mail, it was intended to go to
mailing list.
> >
> > To the point - I think that what you propose with
reordering fields
> > manually shift the load from the tool to the developer. It
will lead to
> > further implementation errors caused by a need to reorder
fields while
> > creating spec. It will be inconsistent with rest of places
where things
> > are in "natural order" (big endian) except one or two types
which
> > collects bit flags which will have to be declared in
different order.
> > What I did in my naive implementation with "little endian"
flag on the
> > State type is re-arrangement of fields during generation
time.
> > It does not require any byte shifting at the runtime and
keeps natural
> > order of fields without the need for manual reordering of
flags in mspec
> > declaration.
> >
> > I understand that keeping mspec simple is an important
priority, however
> > doing it at the cost of developers who will use it to
implement codecs
> > will not help us in long term.
> > I'm quite sure that sooner or later we will get a protocol
with mix of
> > BE/LE fields.
> >
> > Cheers,
> > Łukasz
> >
> >
> > On 14.04.2020 14:57, Christofer Dutz wrote:
> > > Hi Lukasz (adding dev@ to the recipients again)
> > >
> > >
> > >
> > > you are not quite correct. Enum types do declare a base
type where they
> > > are declared … not where they are used.
> > >
> > >
> > >
> > > If you have bit-fields then why don’t you define them as
sequence of
> > > bits? I really can’t understand why you need to flip
anything.
> > >
> > > I think you’re trying to do something similar to
Sebastian when he
> > > wanted to introduce some bit-mask types.
> > >
> > >
> > >
> > > I could imagine that in the spec it might be written …
these two bytes
> > > are a bit-mask and the bit 1 means X bit 10 means Y, …
> > >
> > > So why not define the bit fields in the sequence they are
sent over the
> > > wire?
> > >
> > >
> > >
> > > Assuming you have a bit field of 16 bits BE uint. If the
spec now says:
> > >
> > >
> > >
> > >
> > >
> > > Bit: 15|14|13|12|11|10|9 |8 |7 |6
|5 |4 |3 |2
> > > |1 |0
> > >
> > > Meaning: A |B |C |D |E | F |G|H |I | J
| K |L | M|N |O |P
> > >
> > >
> > >
> > > Then the order they are sent is:
> > >
> > > 7 |6 |5 |4 |3 |2 |1 |0 | 15|14|13|12|11|10|9 |8
> > >
> > > So you have to declare the bit fields in the order:
> > >
> > > I | J | K |L | M|N |O |P
|A |B |C |D
> > > |E | F |G|H
> > >
> > >
> > >
> > > So I don’t quite understand what you’re trying to flip
here.
> > >
> > >
> > >
> > > Chris
> > >
> > >
> > >
> > > *Von: *Łukasz Dywicki <l...@code-house.org>
> > > *Datum: *Dienstag, 14. April 2020 um 13:26
> > > *An: *Christofer Dutz <christofer.d...@c-ware.de>
> > > *Betreff: *Re: Big and littleendian fields in one mspec
> > >
> > >
> > >
> > > I've added the endianness switch to the types in my
experiments. These
> > > are not needed for enums as these are read as int and
then mapped to
> > > constants. I referred to these as an example - enum does
have a length
> > > indication and type behind it.
> > >
> > >
> > >
> > > Again, I will bring the issue - StateIO currently fails
to do anything
> > > useful due to BE/LE switch. Because this type uses single
bits which
> > > need to be flipped before reading or after writing
otherwise they end up
> > > in improper order. Out of 16 bits 9 are in use so we have
a lot of
> > > possible combinations (2^9), which seems too much to
create an enum.
> > >
> > > Since you didn't like my initial proposal and
modifications (as they
> > > might be redundant to what is available in the buffer
API), how would
> > > you handle State serialization without affecting mspec
and without
> > > further complication to code generation?
> > >
> > >
> > >
> > > Best,
> > >
> > > Łukasz
> > >
> > >
> > >
> > > wt., 14 kwi 2020 o 12:47 Christofer Dutz
<christofer.d...@c-ware.de
> > > <mailto:christofer.d...@c-ware.de>> napisał(a):
> > >
> > > Hi Lukasz,
> > >
> > > but we don't have a:
> > > [enum uint 16 little endian 'CommandId']
> > > But only a:
> > > [enum uint 16 'CommandId']
> > >
> > > And in your case I think perhaps the constants are
not correct. So
> > > having a 16 bit uint will result in a 4 digit hex
string:
> > > So if you are having problems in mapping them to your
constants,
> > > perhaps the constants are in the wrong endianness.
> > >
> > > I have encountered (but can't recall where) that the
Enum constants
> > > in a BE protocol were written down in LE notation.
> > > Of course the thing can't work then.
> > >
> > > So if for example you have the constant "1" in a BE
protocol with a
> > > uint 16 enum type, your constant is not 0x0001, but
0x0100 instead.
> > >
> > > Chris
> > >
> > >
> > >
> > >
> > > Am 14.04.20, 12:37 schrieb "Łukasz Dywicki"
<l...@code-house.org
> > > <mailto:l...@code-house.org>>:
> > >
> > > The legendary "two bytes" (shall we create a band
with this
> > > name?!) are
> > > coming from unfortunate State type. I don't mind
these to be an
> > > int/sint/uint or whathever - this is matter of
interpretation.
> > >
> > > If you could please check again my earlier
messages you will find
> > > struggle I have which is - how much given type
takes.
> > >
> > > We have that for enums
> > > [enum uint 16 little endian 'CommandId']
> > >
> > > but we don't have that for complex types
> > > [type 'State']
> > >
> > > This leads to situation that we don't know how to
read and interpret
> > > incoming byte sequence or how to properly write
it back to stream.
> > >
> > > It would be great if we could limit the issue
just to
> > > // read
> > > state =
StateIO.parseStatic(io.readUnsignedInt(16, true)); //
> > > true->LE
> > > // write
> > > wio = new WriteBuffer(2);
> > > StateIO.staticSerialize(wio, new State(...));
> > > io.writeUnsignedInt(8, wio.read, true); //
true->LE
> > >
> > > However to do that first we need to know that
State is a uint 16
> > > LE and
> > > then do a lot of mambo-jambo in code generators
to cope with
> > > that. :-)
> > >
> > > Best,
> > > Łukasz
> > >
> > >
> > > On 14.04.2020 12:20, Christofer Dutz wrote:
> > > > Oh gee ... I totally remember having exactly
the same
> > > discussion with Sebastian about "bytes" ...
> > > >
> > > > The problem is there is generally no "byte"
"int" and "uint"
> > > because a byte = 8 bits is either signed or unsigned.
That should
> > > the 3rd option be? Perhaps-signed?
> > > > So generally I use "uint 8" for what you refer
to as a "byte 8".
> > > >
> > > > Wo what would be the difference between your "2
byte little
> > > endian" and an "uint 16" with a LE ReadBuffer?
> > > >
> > > > I think what you have to rid yourself of
thinking of int as
> > > number and a byte not being a number.
> > > >
> > > > Chris
> > > >
> > > >
> > > >
> > > > Am 14.04.20, 10:52 schrieb "Łukasz Dywicki"
> > > <l...@code-house.org <mailto:l...@code-house.org>>:
> > > >
> > > > Hey Christian,
> > > > The problem I face is quite simple. State
type in mspec i
> > > declared as a
> > > > bunch of bits. Type length is fixed,
however not available
> > > anywhere in
> > > > mspec or code generator to re-arrange bytes
upfront. All
> > > we have exposed
> > > > at reader/write level is read/write bit.
> > > > To be fair LE/BE support in read/write
buffers is limited
> > > just to
> > > > numbers. There is no such support for raw
bytes or bits,
> > > cause for that
> > > > you need to declare a length of LE/BE
sequence.
> > > >
> > > > I would love if I could just declare State
as '2 byte
> > > little endian' so
> > > > it would be read properly upfront and
parsed with no
> > > changes in
> > > > generated code, however I'm not sure how to
do it and
> > > where. That's why
> > > > I'm playing with different things described
in earlier mail.
> > > > Since all type handling is general I am
just afraid of
> > > more complicated
> > > > scenarios where we have variable length
structures such as
> > > arrays.
> > > >
> > > > Best regards,
> > > > Łukasz
> > > >
> > > >
> > > > On 14.04.2020 09:41, Christofer Dutz wrote:
> > > > > Hi Lukasz,
> > > > >
> > > > > I am not sure I am understanding the
problems you are
> > > facing. We already have LE and BE protocols.
> > > > > For example EIP is LE and the rest is
generally BE. It
> > > seems that ADS/AMS is also LE.
> > > > > mspec doesn't even know about endianness.
> > > > >
> > > > > Up till now the endianness doesn't have
an effect on
> > > bit-fields or single-bit ints.
> > > > > It only starts to affect if a field goes
from one byte
> > > to the next, which is usually for (u)int and floating
point values.
> > > > >
> > > > > That's why we have created the
Read/WriteBuffers to set
> > > their endianness in the constructor.
> > > > >
> > > > > So if you're creating a driver for
ADS/AMS which is LE,
> > > then you write the mspec according to the sequence
the information
> > > is located in the transferred bytes and have the
Read/WriteBuffer
> > > handle the endianness issue.
> > > > >
> > > > > I do see a problem when there are drivers
that use mixed
> > > endianness, but we have still to encounter such a
protocol.
> > > > >
> > > > > So I have to admit that I don't like any
of the mspec
> > > changes you proposed, as I think you are just not
using the tools we
> > > have the right way.
> > > > >
> > > > > Chris
> > > > >
> > > > >
> > > > >
> > > > > Am 14.04.20, 00:32 schrieb "Łukasz
Dywicki"
> > > <l...@code-house.org <mailto:l...@code-house.org>>:
> > > > >
> > > > > Hey Niclas,
> > > > > I realized how old the old things are
when I started
> > > preparing
> > > > > automation training for mere mortals
and got into
> > > history of frames and
> > > > > even cabling. Mr. Modbus and EIA-485
is definitely
> > > older than I. ;-)
> > > > >
> > > > > Getting back to the point - yes. I
been thinking how
> > > to address the byte
> > > > > order in effective way. Here are two
approaches I
> > > have for now:
> > > > >
> > > > > A) My initial attempt is just a
temporary buffer
> > > which is then written
> > > > > in reverse order to caller. For
reading it is
> > > similar - just getting N
> > > > > bytes in reversed order. The hard
part is.. knowing
> > > N. I had to add a
> > > > > static calculation in order to
allocate valid buffer
> > > sizes. I tend to
> > > > > work but I'm not happy with this
approach cause it
> > > involves additional work.
> > > > > B) Second idea I've got is really
simple and relies
> > > on code generation.
> > > > > We know in which order fields are
coming. Here I'm
> > > referring to a State
> > > > > field which is just bunch of bits. If
we would group
> > > fields in bytes and
> > > > > generate code in reverse order then
it has chance to
> > > work. Requirement
> > > > > for that - ability to know basic
field sizes upfront.
> > > > > C) Try to combine above with bit-io or
> > > Read/WriteBuffers as these are
> > > > > places which know actual position and
state of
> > > buffers which are being
> > > > > read/written.
> > > > >
> > > > > Now, getting to two cases which are a
problem.
> > > CommandId and State. So
> > > > > with command id situation is simple
as it is
> > > declared as enum and it is
> > > > > read as uint. We know size upfront
and can generate
> > > valid method call
> > > > > (readIntLE).
> > > > > [enum uint 16 little endian
'CommandId'
> > > > > ['0x00' INVALID]
> > > > > ['0x01' ADS_READ_DEVICE_INFO]
> > > > > ['0x02' ADS_READ]
> > > > > ['0x03' ADS_WRITE]
> > > > > ['0x04' ADS_READ_STATE]
> > > > > ['0x05' ADS_WRITE_CONTROL]
> > > > > ['0x06'
ADS_ADD_DEVICE_NOTIFICATION]
> > > > > ['0x07'
ADS_DELETE_DEVICE_NOTIFICATION]
> > > > > ['0x08' ADS_DEVICE_NOTIFICATION]
> > > > > ['0x09' ADS_READ_WRITE]
> > > > > ]
> > > > >
> > > > > Second candidate is what I'm stuck
right now sniping
> > > next cycles of
> > > > > problems. So in case of State we have
complex type
> > > composed from 2
> > > > > bytes. A note here - instead of two
bytes we might
> > > have a variable
> > > > > length type which includes array or
other variable
> > > section.
> > > > > [type little endian 'State'
> > > > > [simple bit 'broadcast'
]
> > > > > [reserved int 7 '0x0'
]
> > > > > [simple bit 'initCommand'
]
> > > > > [simple bit 'updCommand'
]
> > > > > [simple bit 'timestampAdded'
]
> > > > > [simple bit
'highPriorityCommand' ]
> > > > > [simple bit 'systemCommand'
]
> > > > > [simple bit 'adsCommand'
]
> > > > > [simple bit 'noReturn'
]
> > > > > [simple bit 'response'
]
> > > > > ]
> > > > >
> > > > > The order of reading big endian
encoded data to
> > > impose little endian
> > > > > shift would be (please correct me if
I'm wrong):
> > > > > 1) init
> > > > > 2) udp
> > > > > 3) add timestamp
> > > > > 4) priority
> > > > > 5) system
> > > > > 6) ads
> > > > > 7) noreturn
> > > > > 8) response (end of byte 1)
> > > > > 9) broadcast
> > > > > 10) reserved (end of byte )
> > > > > We can do same trick for writing, by
re-arranging
> > > fields. By this way we
> > > > > avoid any additional byte level
operations.
> > > > >
> > > > > Overall trouble with generated driver
is to declare
> > > "how much" bytes
> > > > > should be read and interpreted. We
have precise size
> > > information at the
> > > > > runtime - due to length fields, we
can leverage it
> > > at generation time,
> > > > > but then we won't be able to cover
all cases.
> > > > >
> > > > > I would love to keep it simple and do
not break
> > > things thus I need your
> > > > > advice on how to approach this
problem in a valid way.
> > > > >
> > > > > Cheers,
> > > > > Łukasz
> > > > >
> > > > >
> > > > > On 13.04.2020 03:26, Niclas Hedhman
wrote:
> > > > > > <anecdotal-rant>
> > > > > > For us who were around and shaping
the protocols
> > > in the 1980s, and people
> > > > > > before us (and before standards
like RS-232), a
> > > lot of the "specifications"
> > > > > > came out of "observation of
implementation we
> > > managed to get to work",
> > > > > > rather than "implement this spec".
A lot was due
> > > to extreme memory
> > > > > > constraints (in my case,
multi-tasking operating
> > > system, serial protocol
> > > > > > 187kbps, interpreted programming
language with
> > > floating point ops and user
> > > > > > applications in 2kB RAM and 8kB
EPROM) and a
> > > general lack of information,
> > > > > > like what other people were doing,
sharing
> > > experiences and so on.
> > > > > >
> > > > > > And there were many "innovative"
ways to squeeze
> > > just a little bit extra
> > > > > > out of the hardware, resulting in
"hard to
> > > understand" consequences. Bit
> > > > > > packing was a typical one, multiple
functions
> > > packed into a single byte.
> > > > > > Look at page 14 in
> > > https://www.nxp.com/docs/en/data-sheet/80C31_80C32.pdf
> > > > > > and read up on "UART Enahanced
Mode", and we used
> > > this, i.e. 9 bits, no
> > > > > > parity and clever use of address
and mask to
> > > create a slave-to-slave direct
> > > > > > protocol, where the master's role
was to signal
> > > which slave "owned" the
> > > > > > cable. Yeah, in that 8kB ROM
limitation (I think
> > > protocol was about 1kB
> > > > > > ROM) and something like 150 bytes
RAM for comm
> > > protocol.
> > > > > >
> > > > > > Could you implement a compatible
device to this
> > > with PLC4X and modern
> > > > > > hardware (i.e. no 8031/32
co-processor)? Possibly
> > > but bit-banging is needed
> > > > > > to support the 9bit data (+start
and stop bits)
> > > and an awful lot of CPU
> > > > > > cycles on something that was
automatic on one of
> > > the slowest long-lived
> > > > > > microcontroller ever.
> > > > > > </anecdotal-rant>
> > > > > >
> > > > > > My point was only to highlight that
some of the
> > > strange things you see in
> > > > > > protocols today, have its roots in
> > > pre-standardization days. Today no one
> > > > > > would go down that route, because
the hardware
> > > cost nothing now (8031 +
> > > > > > 8kB EPROM + 2kB static RAM +
battery backup =>
> > > ~$50 in 1983's currency) and
> > > > > > longevity of software is more
important.
> > > > > >
> > > > > > Cheers
> > > > > > Niclas
> > > > > >
> > > > > >
> > > > > > On Sun, Apr 12, 2020 at 10:10 PM
Christofer Dutz
> > > <christofer.d...@c-ware.de
<mailto:christofer.d...@c-ware.de>>
> > > > > > wrote:
> > > > > >
> > > > > >> Hi Lukasz,
> > > > > >>
> > > > > >> I think it really gets tricky when
using BE and
> > > having some byte-odd-sizes
> > > > > >> ... I remember in the Firmata
protocol there were
> > > some bitmasks and then 10
> > > > > >> bit uint as BE ... not it really
got tricky as
> > > the specs were written from
> > > > > >> a point of view: You read 16 bits
BE and then the
> > > first6 bits mean XYZ
> > > > > >> instead of describing how the bits
actually
> > > travel over the wire.
> > > > > >>
> > > > > >> Chris
> > > > > >>
> > > > > >>
> > > > > >>
> > > > > >> Am 11.04.20, 01:21 schrieb "Łukasz
Dywicki"
> > > <l...@code-house.org <mailto:l...@code-house.org>>:
> > > > > >>
> > > > > >> I've made some progress with
topic by
> > > modyfing mspec and allowing
> > > > > >> 'little endian' flag on
fields. This moved me
> > > further to next issue -
> > > > > >> which is whole type encoded
little endian.
> > > > > >>
> > > > > >> In ADS driver such type is
State, which has 2
> > > bytes and uses 8 bits for
> > > > > >> various flags.
> > > > > >> There are two cases which
require different
> > > approach - reading and
> > > > > >> writing. So for reading we
need to swap N
> > > bytes based on type length.
> > > > > >> For writing we need to alocate
buffer for N
> > > bytes and swap them before
> > > > > >> writing.
> > > > > >>
> > > > > >> I am stuck now with freemaker
templates and
> > > bit-io.
> > > > > >>
> > > > > >> Cheers,
> > > > > >> Łukasz
> > > > > >>
> > > > > >>
> > > > > >>
> > > > > >> On 10.04.2020 17:57, Łukasz
Dywicki wrote:
> > > > > >> > I am doing some tests of ADS
serialization.
> > > > > >> >
> > > > > >> > I've run into some troubles
with payload
> > > which is generated with new
> > > > > >> > driver. I'm not sure if
that's my fault or
> > > generated code.
> > > > > >> >
> > > > > >> > I did a verification of what
Wireshark
> > > shows and how ads structures
> > > > > >> are
> > > > > >> > parsed. There is a gap I
think. For example
> > > ams port number 1000
> > > > > >> > (0x1027) is read as 4135.
> > > > > >> >
> > > > > >> > Obviously I used wrong
structures while
> > > implementing protocol logic
> > > > > >> in
> > > > > >> > first place, but now I am
uncertain of how
> > > fields are encoded. How we
> > > > > >> > mark field as little endian
when rest of
> > > payload is big endian? Do we
> > > > > >> > have `uint_le`?
> > > > > >> >
> > > > > >> > As far I remember route
creation logic I
> > > was tracking last week used
> > > > > >> > combination of LE and BE.
> > > > > >> >
> > > > > >> > Best regards,
> > > > > >> > Łukasz
> > > > > >> >
> > > > > >>
> > > > > >>
> > > > > >>
> > > > > >
> > > > >
> > > > >
> > > >
> > > >
> > >
> >
> >
>
>
