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STM8L serial half duplex problem

Question asked by Zak on May 16, 2013
Latest reply on Sep 25, 2013 by mcwiggin.patrick
Hi,

I have a problem with USART half duplex.  The output from my STM8L device is too strange.

wave.png

The first half (about 10 bytes) is from host.  My device can receive this well.  After that, the host is wait to receive the data from my device immediately.

When my device starts to send back data to the host, the signal level is down about 300uSec.  After that, the level is back.  What is this ???

I try to do same thing with full duplex mode with connected Tx-Rx.  It looks like work well but same level down is happened between host changed Rx and my device changed Tx.
I try to set the mode of GPIO on same pin to both floating input and open drain output.  But the result is same.
I try to use remapped USART (PC5-6).  But the result is same.
I have another device that is not STM works well.....Oops.

Does anyone know what is wrong with me ?  Any suggestion is welcome.

Best Regards,
Zak

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