UART sending BREAK condition on ATmega128

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Papabravo
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Posted by Papabravo: Wed. Jan 27, 2010 - 06:49 PM
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I'd like to know if there is a recommended way to send a BREAK condition on UART0 or UART1 in the ATmega128. Some UARTS on other processors implement this as a bit in one of the UART control registers.

My initial thought is to disable the transmitter, pull the TxD pin low for the required time, take it high again and re-enable the transmitter.

There may or may not be other ways; that is why I'm asking.

We never have time to do it right,
but we always have time to do it over

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AVR Microcontrollers, megaAVR and tinyAVR, ATmega128
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Silver Markclawson
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Posted by clawson: Wed. Jan 27, 2010 - 07:07 PM
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Quote:

My initial thought is to disable the transmitter, pull the TxD pin low for the required time, take it high again and re-enable the transmitter.

I'm pretty sure that IS the way folks do it.

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Dusza
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Posted by Dusza: Thu. Jan 28, 2010 - 02:05 PM
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You can change uart's baudrate to lower value and send 0x00 byte. (e.g. 0x00 byte transmitted with baud=57600 is break condition for baud=115200)

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Papabravo
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Posted by Papabravo: Thu. Jan 28, 2010 - 05:22 PM
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Dusza wrote:
You can change uart's baudrate to lower value and send 0x00 byte. (e.g. 0x00 byte transmitted with baud=57600 is break condition for baud=115200)

That is a clever alternative. I will be trying both methods. Thanks to both of you.

We never have time to do it right,
but we always have time to do it over

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Papabravo
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Posted by Papabravo: Fri. Jan 29, 2010 - 09:41 PM
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I thought it might be useful to post the code snipet I came up with for sending a BREAK condition on USART1 on an ATmega128L. I chose the method of disabling the transmitter and pulling the TxD line low instead of changing the Baudrate and sending nulls.

Attachment(s): 

File Code fragment for sp_Break() function

We never have time to do it right,
but we always have time to do it over

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