How do I write a Bitstring Presentvalue?

[Chris-Wang-bjc]

I can't write a Bitstring Presentvalue right now, the error info is: TypeError('invalid constructor datatype')

[bbartling]

If you dont mind me asking, what is a BitString or what is your use case? Strings over BACnet?

So it looks like in bacpypes objects.py there is such a thing.

Make sure your syntax is same as BACpypes...Maybe something like if I correctly - bitstringValue presentValue instead of Bitstring Presentvalue:

BAC0 read request:

read_vals = f'{address} bitstringValue {object_instance} presentValue'

What does your code look like?

[Chris-Wang-bjc]

@bbartling Thanks for your reply. Sorry, I may not have explained my problem, it's write property service, not read property service. There is no problem with my code syntax, I can write the presentValue of other data types correctly, but the presentValue of "BitString" data type, when I use the same syntax to write a presentValue of this data type, it throws "TypeError('invalid constructor datatype')", so, can you please try to write a presentValue whose data type is BitString? Thanks!

[bbartling]

Can you show your code? I can see if I can get it to work on my end.

[bbartling]

Another thing you may want to do is find out if your device supports BitString data type.

[Chris-Wang-bjc]

Here is my code. I'm not sure the format of the "presentvalue" that I write correctly. I'm sure my device supports BitString data type, because I'm trying write it by VTS, it's successful. So please help me check it on your device, thanks!

[bbartling]

try getting rid of the curly brackets? {} ...I personally have never heard of bitString before with BACnet. What is your application again? HVAC in the field or security system? Or are you a BACnet developer on a test bench testing your real device with BAC0?

[ChristianTremblay]

BAC0 does not support Bitstring actually. To make it work, you could get inspiration from https://github.com/ChristianTremblay/BAC0/blob/master/BAC0/core/functions/Text.py

and build the request.

Bottom line is :

• you create a complete request that will be sent to IOCB with deferred
• in this request, the value will be "cast" to BitString in some way

A little trial and errors will probably be required.

I don't have any controller at hand support BitString....impossible for me to test for now.

[Chris-Wang-bjc]

Thank you very much, I will take more try.

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