I now tested both versions. With 9600 the sensor will not recognized on the transmitter and with 9800 the RPM value resultats are more worse as with the original 9700 version. Same behavior with the REX 10 receiver..
Thx Tero fro you comment. I now tested a original Arduino board to make sure that it does not depend on the board type I use. Unfortunately same behaviour. I know there are different libraries out there. Which one did you use/tested with your code? I was a programmer in my early live (30 years ago ) and may can check the different libraries with your code.
I am moving to Sepp's true EX-library just for these reasons. Conversion is a bit slow, all the menu's etc needs to be rebuilt. Also there is the eternal question about Arduino's interrupts, some sensors might not be convertable.
As now, all the sensors are working with some serial speed. I know it's not ideal. Everything was fine before REX came