avr - ATmega168: UART 8 data bits, no parity, 1 stop bit

According to the datasheet I'm setting the UCSR0C register as following:

UCSR0C = 0b00000110

Description:

Bit   0:   0: TX rising, RX falling
Bit 2-1:  11: character size 8 bit
Bit   3:   0: 1 stop bit
Bit 5-4:  00: no parity
Bit 7-6:  00: asynchronous USART

(http://www.atmel.com/images/doc2545.pdf page 193)

Although I configured the UART to use 8 bit data mode I have to set my communicating terminal (picocom) to use 7 bit data mode. Otherwise I don't get correct data from my ATmega168. I also tried to use minicom and miniterm.py.

My target device I want to communicate with is a Raspberry Pi. I'm using Peter Fleury's UART library (http://homepage.hispeed.ch/peterfleury/group__pfleury__uart.html).

Any ideas what I'm be doing wrong? Did I forget something?

Answer

I solved the problem by using an external oscillator. It seems that the internal oscillator is too imprecise for UART communication.