ATmega328p usart problem

[fm101]

hi, I have problem with ATmega328p USART(reading message on PC terminal sent by atmega328p). Followings are diagnostics.

- works with 11.0592MHz external crystal oscillator
- works with 8MHz internal RC oscillator
- code works as evident from working successfully with 11.0592MHz and 8MHz int. osc test
- no problem in terminal baud rate and other settings
- no problem with UBRR value(taken from datasheet)
But,
- does not work with 16MHz and 4MHz external crystal oscillator

Also, I am using USB to TTL converter.

What else besides above can i look for and do to test?

thanks

 

[KlausST]

Hi,

Forum rules say:

Only you know what "doesn't work" means
Please tell us what your circuit or code is supposed to do and why it "doesn't work".When you come in and say "it doesn't work" or just "it has errors", that means NOTHING. There could be a million things wrong and no one will know where to look.

Klaus

 

[FvM]

Did you verify that the processor is executing code at all?

Due to lack of detail information, we can't check the processor configuration. Provided it's correc, there could be a problem with the crystal or external oscillator components. Utimately you'd check the actual baud rate with an oscilloscope.

 

[ctownsend]

did you program the fuses to use the external clock?

post your usart code.