Finally I have got the VB program working! (I got rusty programming in VB)

The values are received as a string and decoded extracting the ASCII value from any single character of the string. Comparison with what has been sent was ok all the time for all the values including the CRC values (both inverted and not inverted).

So now I have to blame only ANDROID for the strange behavior, but still difficult to understand (at least for me) why the problem is only with the inverted byte! But since I have not too much knowledge of this OS, I could not dig any further at the moment.

Thanks to all.

Alberto