Hi J,Oshonsoft interpreters all integers as positive.
For example 16 bit word as 0-65535.
When you know, that the integer is 2's complement, you must take care of the sign in the program.
You can do it easily by converting the signed integer to a floating point variable ( see msg #12 ), as was done in the BMP280 calculation or carry the sign in a separate variable.
My point is that, when receiving 2's complement, I would only be able to alter it after it has been gleaned by Oshonsoft, so would it have been corrupted in any way before applying (msg#12)?