AVR-Chat

Hi Jim.  

Should you be using the AVR GCC compiler, you are welcome to some 
code I wrote to implement a full-duplex software UART.  The function 
is set up to be called at 4x the baud rate you want.  I run it at 
4800 baud (ie. it's called at 19.2kHz) for a GPS receiver, but 9600 
works just fine too (when called at 38.4kHz).  This is on an ATmega8 
running at 14.7456mHz and I haven't had any problems.

But to answer your question: 
In TTL (I/O pin), idle is high, and the start bit is low.
In RS-232, idle is low, and the start bit is high.
You can find this and more on page 134 of the ATmega8 manual.

-Gary

--- In AVR-Chat@yahoogroups.com, James Washer <washer@t...> wrote:
>
> I need to implement a bit-bang serial port. It's my understanding 
the RS232 "idles" high, which would mean the logic level out of a 
max232 would be low. The start bit would then be logic high to the 
AVR.. Is this correct?
> 
> thanks
> 
>  - jim
>