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Write negative Number to Drive with C++ interface

Anonymous
Not applicable

Write negative Number to Drive with C++ interface

I want to write a negative value to a paramter on the CtrlX Drive. Via Drive Engineering a decimal number can be written to the parameter which can be negative. This is not possible via the C++ interface, because there the number to write is a vector of byte, which holds no information about the number being positive or negative. Is it possible to write negative number via the C++ interface on the CtrlX and if yes how?

In my particular case it is the paramter "S-0-0052, Reference distance of encoder 1". This parameter can be positive and negative. 2022-02-07_11h36_15.png

Its format is DEC_MV(Signed decimal number). But in the C++ interface the data to send is a vector of uint8_t so a vector of unsigned numbers. Is there a logical conversion to a negative number? I have tried to set the first bit to 1, representing the minus bit for a signed, but this does not work.

 

auto data__ = data ? _fbb.CreateVector<uint8_t>(*data)

 

source: sdk/include/comm.ethercat.master/comm/ethercat/master/fbs/parameter_generated.h
 
Also the decimal place in the documentation is emtpy, which implies for me it is 0. After testing I found out it is actually 4.
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CodeShepherd
Community Moderator

Re: Write negative Number to Drive with C++ interface

Changing only the first bit could be not enough depending on the data size. Here an example simply made with the calculator:

CodeShepherd_0-1644396708294.png

 

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