[En-Nut-Discussion] Connecting Ethernut 1.3 with ATMega32 via UART

[Ulrich Prinz]

Hi!

If the voltage levels of both systems are the same, a driver or level 
shifter is not needed. Keep two things in mind:
1) With logic level the distance of the connection is way shorter than 
with V24 levels. So external interference has more impact on your 
connection. You can avoid problems by keeping short connections or 
slower data rates.
2) Same voltage level means that both system have to be on 5V or 3.3V. 
With AVR you cannot mix 5V and 3.3V as the port is limited to Vcc+0.5V. 
The 5V system might kill the 3.3V systems port through the latch-up 
effect. You can interface systems with different logic levels with chips 
like TIs 74AVC series or you can use buffers that are 5V tolerant even 
they are powered with 3.3V.

Best regards, Ulrich


Am 14.03.2010 00:51, schrieb Hanrun Hu:
> Hello,
>
> normally, if connecting ATMega32 via UART with a PC, one needs a converter in between, as the -12V/+12V of the PC have to be converted to the 5V/0V of the microcontroller. Is this also the case, if I want to connect the UART from Ethernut with my ATMega32?
>
> Hanrun
>
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