Hi Ben ...
Sorry for my email... I should really finish reading before replying :-(
About your suggestion to add it to the type to the ModbusField ... I agree. But
I would simply extend the Address string the same way the TIA addresses were
extended.
Cause the problem I'm seeing is that for the 61131 datatypes we can provide an
enum, but not for any custom types the driver might be supporting. With a
String we can keep it simple ... check if the type is a 61131 type -> if yes:
do the default handling. If it's not, use some driver specific
encoding/decoding.
In my particular case the Float values were also 4 byte values ... I manually
solved it by requesting 2 element arrays for every float address (The map of
reigsters only used only even register numbers, so that worked). Then I
manually converted the 2 x 2bytes into a 4byte float with this code:
// Decode the first 10 shorts as 32bit floats ...
StringBuilder sb = new StringBuilder();
for(int i = 0; i < 10; i++) {
int short1 = value.getIndex(i * 2).getInteger();
int short2 = value.getIndex((i * 2) + 1).getInteger();
WriteBuffer wb = new WriteBuffer(4);
wb.writeInt(16, short1);
wb.writeInt(16, short2);
final byte[] data = wb.getData();
int intVal = (data[3] & 0xFF) | ((data[2] & 0xFF) << 8) |
((data[1] & 0xFF) << 16) | ((data[0] & 0xFF) << 24);
final float v1 = Float.intBitsToFloat(intVal);
sb.append(v1).append(", ");
}
Ok in this case I read 10 floats by reading an array of 20 registers. Guess it
should be even simpler with 32bit integers
But I guess it does the job ... not pretty, but it works and I would definitely
love to have something similar in the drivers to handle this if I said
"holding-register:1000[10]:REAL"
Chris
Am 08.09.20, 13:59 schrieb "Christofer Dutz" <[email protected]>:
Hi Ben,
if you have followed the latest discussions here ... currently the modbus
protocol supports 16bit integer values for registers and Boolean values for
coils.
The protocol doesn't directly support anything else. However I have seen
that vendors use arrays of registers to support higher level types. In my
special case the PLC vendor used two 16bit integers to provide 32bit float
values.
We will probably start adding support for the basic IEC 61131 datatypes
(https://en.wikipedia.org/wiki/IEC_61131-3) but I think this will only apply
for the Bool, Bit-String, Signed and Unsigned Integers as well as Real values.
Durations, Times, Dates and especially Strings will be problematic as it seems
every vendor uses a different encoding of these.
Chris
Am 08.09.20, 13:52 schrieb "Ben Hutcheson" <[email protected]>:
Hi,
Looking at the example I had with the hello-world-write example trying
to
write a String to the Modbus protocol.
ava -jar plc4j-hello-world-plc4x-write-0.8.0-SNAPSHOT-uber-jar.jar
--connection-string modbus://127.0.0.1:5467 --field-addresses 40010
-field-values 32000
The value 32000 then gets cast as a String and is passed to the
encodeString function in ModbusFieldHandler. (It doesn't have one it
gets
passed to the DefaultFieldHandler). To get this to work properly we
would
need to define a datatype to cast the String to, S7 does this already
and
with the consensus that IEC 61131 data types be used where possible
then I
see no reason we shouldn't add the datatype field to the ModbusField.
If we
are doing this for these protocols, then why don't we add the datatype
field to the PLCField interface, this would allow us to use the same
default encodeString (We may have to map the protocol specific
datatypes to
IEC 61131 here, the same internalEncodeString might be better) functions
for S7 and Modbus by casting the input to a PLCField instead of a
S7Field
or ModbusField.
When encodeString is then called we can use the datatype that is passed
to
it to encode it to a PLCInteger/PLCFloat/etc.., the same way the S7
protocol does it. S7 however only allows Strings to be passed as string
related variables (CHAR, WCHAR, STRING and WSTRING), I don't see any
reason
we can't expand this to be able to pass any PLC datatype from a string.
The next problem I had was to then be able to parse the PLCInteger
class to
a byte array within the fromPLCValue function. For the UINT datatype for
the Modbus protocol, this is a 2 byte array however the PLCInteger class
contains it as a 4 byte array. in the fromPLCValue function there
doesn't
seem to be a way to test to see if it is an UINT or a 4 byte integer
such
as a DINT. If we were to change the classes in
plc4j/api/src/main/java/org/apache/plc4x/java/api/value to match the IEC
61131 datatypes then we should be able to parse them correctly in Modbus
fromPLCValue function.
I have probably missed a few things out, like how the TransportSize
class
for the S7 protocol works, and we may have to settle for mapping
protocol
specific types to IEC61131 types in the encode functions in each
protocol,
what are your thoughts?
Kind Regards
Ben
On Sun, Sep 6, 2020 at 11:25 AM Christofer Dutz
<[email protected]>
wrote:
> Hi all,
>
> well I doubt that we could really centrally handle this.
> If you have an idea how to unify this, I'd be happy for a suggestion.
> I guess most will have to be handled in the individual drivers
themselves.
>
> But I really would like all drivers to support the same base-set of
> datatypes.
>
> Chris
>
>
>
> Am 06.09.20, 17:02 schrieb "Cesar Garcia" <[email protected]>:
>
> Hello,
>
> I think it can be applied from several points of view, the one
> typified as
> you indicate (HREGISTER: REAL) or (HREGISTER [2]), each one has
its
> advantage.
>
> To be able to handle the types indifferently (specifically between
> Modbus
> and S7), I modify the field of the Modbus driver so that it
strictly
> adapts
> to the PLC4X API. This prevents the user's App from having to
implement
> code to interpret the content of the records.
>
> This is implemented in version 0.6.1 of PLC4X, but the new
version is
> something else.
>
> Best regards,
>
> El dom., 6 sept. 2020 a las 10:03, Ben Hutcheson (<
> [email protected]>)
> escribió:
>
> > Hi,
> >
> > I ran into this issue this morning when using the
hello-world-write
> example
> > and trying to write to a Modbus connection. It looks like it
assumed
> the
> > input value is a string whereas the Modbus protocol doesn't have
> support
> > for it yet.
> >
> > I was thinking about expanding
> >
> >
>
github/plc4x/plc4j/spi/src/main/java/org/apache/plc4x/java/spi/connection/DefaultPlcFieldHandler.java
> > to include default handlers for the various IEEE 61131 data
types,
> the
> > specific protocols can then override them as necessary?
> >
> > Kind Regards
> >
> > Ben
> >
> > On Wed, Sep 2, 2020 at 9:36 AM Christofer Dutz <
> [email protected]>
> > wrote:
> >
> > > Hi Julian,
> > >
> > > I agree ... if one driver would define an "INT" as 32bit
integer
> and the
> > > others would treat it as 16bit ... that could be a problem.
> > > Perhaps having a statement of the project that we use the IEC
> 61131 types
> > > as a basis and if you want to use a given protocols different
> types, that
> > > you can prefix them ..
> > >
> > > Assuming a driver for the famous "HURZ" protocol would use
32bit
> INTs,
> > > then an "INT" could reference the 16bit version and a
"HURZ_INT"
> could be
> > > the 32bit version?
> > >
> > > Chris
> > >
> > >
> > >
> > >
> > > Am 02.09.20, 15:26 schrieb "Julian Feinauer" <
> > > [email protected]>:
> > >
> > > Hi,
> > >
> > > agree with your suggestion!
> > > Although we have to be careful to not mix it up with
specific
> > > implementations of datatypes in some drivers.
> > >
> > > Julian
> > >
> > > Am 02.09.20, 15:21 schrieb "Christofer Dutz" <
> > > [email protected]>:
> > >
> > > Hi all,
> > >
> > > today I was at a customer’s site and used the Modbus
> driver to
> > get
> > > data. This generally worked fine.
> > > The thing however I found a little complicated, was
that
> the PLC
> > > seemed to offer all values as 32Bit Floating point values.
> > > So in order to correctly read them, I had to read an
array
> of two
> > > consecutive shorts and then manually convert them into a
float.
> > >
> > > I bet we can do this better.
> > >
> > > So I thought … how about we use the same
> > > https://en.wikipedia.org/wiki/IEC_61131-3 datatypes we are
> already using
> > > in other drivers and for example if you write:
> > >
> > > holding-register:1:REAL
> > >
> > > it would automatically use modbus to read an array of
two
> shorts
> > > and to internally convert these to one REAL/float.
> > >
> > > What do you think? I think we could probably do this
in
> most
> > > drivers.
> > >
> > > Chris
> > >
> > >
> > >
> > >
> > >
> >
>
>
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