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problem with rs232 communication

 
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borg

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Joined: 03 Mar 2005
Posts: 4

PostPosted: Thu Mar 03, 2005 5:46 pm    Post subject: problem with rs232 communication Reply with quote

Hi

Can anybody help me??
I have set the property baudrate on 9600 for the Atmega8535, but i can't get the right sended data on the Pc. On the Oszi i checked the bitrate and I recognized that it was approxmitally 1300.
How can i manage this problem

thanks and sorry for the bad english but i'm from germany

Uwe
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dswinscoe

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Joined: 09 Feb 2005
Posts: 17
Location: London, UK

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PostPosted: Thu Mar 03, 2005 7:12 pm    Post subject: Reply with quote

Check that the speed on your crystal matches the crystal setting for the compiler. I spent ages trying to sort out a problem with serial communication about a month ago only to find that the crystal on the board was 8MHz and the frequency I had set in the compiler was 4MHz. (I cannot read component values without a magnifier these days Sad ).
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borg

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Joined: 03 Mar 2005
Posts: 4

PostPosted: Thu Mar 03, 2005 9:57 pm    Post subject: Reply with quote

No thats not the problem!!
I checked all the speeds. if I use the same configuration for a At90S8535 it works, but when I chose the m8535 and programm the other chip it doesn't work! and the oszi shows another bautrate!
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Luciano

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Joined: 29 Nov 2004
Posts: 3149
Location: Italy

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PostPosted: Thu Mar 03, 2005 11:16 pm    Post subject: Reply with quote

Hi,

Our crystal balls are covered with white frost!
Post your code and tell us the quartz oscillator frequency.

If you have set the baudrate to 9600 and you get 1300, then
you are using the internal oscillator at 1 MHz instead of your
external quartz oscillator running at 7.3728 MHz.

Best regards,

Luciano
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ATIU

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Joined: 15 Oct 2004
Posts: 528

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PostPosted: Fri Mar 04, 2005 12:20 am    Post subject: Reply with quote

Set fuse bit to use external xtal, most of the newer uC are factory set with internal RC osc as default.
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borg

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Joined: 03 Mar 2005
Posts: 4

PostPosted: Fri Mar 04, 2005 3:37 pm    Post subject: Reply with quote

Hi

Thanks a lot! We solved the problems, it was the fusebit and the atmel used the internal frequency of 1MHz

Bye Uwe
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