you said earlier :
"if I want to receive text messages only, I use not a circular buffer.
Any message was written from the start of the receive buffer and if 0x0D or 0x0A was received a flag was set, that a message was complete received.
Then this message can be parsed without problems.
And if it was finished all further received bytes are moved back to the start of the receive buffer and so on. "

How do you handle errors? , what if u didnt get 0x0D or 0x0A for half an hour coz you were in noisy environment. Your buffer would grow and grow till your program crashes. Circular buffers are a must for text or binary messages.
I think its very easy to make things work in ideal conditions and for a short time but the real challenge is to make your circuit reliable and work under all conditions.
Any suggestions how you handle errors ?
Thanx
Mahmood