o5i_:
Ok, i have managed the formula.. Now, at the start of the communication i need to do a fastinit how it ist described in kwp protocol.. I need to put the Serial output for 300ms high than 25ms low and again 25ms low before i can start the serial communication whit 10400baud... or slowinit is 0x33 @ 5 baud...
Can i do "serial.begin(baud)" more than 1 time?
Yes you can but this sounds more like you need a dedicated handshake , setting high and low "manually".
in my (limited) experience the very low baud rates are not that reliable