Reading on Analog Input/Output

[Asclepiios]

Hello,

For a project I need to read the Input and Output of a PLC with python.
I do not have acces to the PLC, but my reading of Input and Output seems to work, since I obtain value and no error.
Here is my code :
data = s7_client.read_area(snap7.types.Areas.PE, 0, starting_byte, size)
Is there a way to read Analog Input/Output ? It seems not possible with snap7.types.Areas.PE since it give me the error :
b'CPU : Address out of range'
Is there a specific Areas that I miss ? I don't see one in the file, or any function ready to read on analog.

with kind regards,
Asclepiios

[swamper123]

Hello there,

first question is: What device and what version of python-snap7 do you got?

[swamper123]

I haven't got a decive to test things. :/
Stupid question: Is that analog Input 12 Bit or one word long? Not sure what Kind of Datatype S7 uses ... it is a part I have never used so much before.

Perhaps @maxitaxi13 can help out, since he used PA/PE as well ...

[Asclepiios]

The analog input seems to be one word long.

When I try to read on an address that is more than 127, I got the b'CPU : Address out of range' error.
But the value between my last Input and 127 are all at 0.

Edit :
Based on this post : https://sourceforge.net/p/snap7/discussion/general/thread/b549eeb3/?limit=25
I tried to read with the Area at 0x80, and I'm able to read at 128 and more.
I have no idea why ? But I still think it's relevant

[swamper123]

Hmm ... no clue ... sorry I have to pass that. 😕

[Asclepiios]

Thanks for the help anyway :)
I will continue to see if there is something to do with that !

[Asclepiios]

Hello,
I may have found part of my problem, so I will give an update :
PEWs are not simply analog input/output in my case but Peripheral Input/Output Word.
Every cycle, the Process image reads all the input and saves them. But it has a limited size, in my case 128 Byte for input, and 128 Byte for the output.

If you want to access I/O outside of this range, you must use Peripheral access. It also gives the real value a the moment, since it doesn't use Process Image.
The input/output area in snap7 may use Process Image, making it impossible to read outside of this range.
There may be another area for that, not implemented, as I was saying last time maybe the 0x80. I will try things if I happen to get a PLC in my hand.
(The Area 0x80 is encouraged by the WireShark github, line 333 here)

(More info about Peripheral Access, and Process Image here)