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IMX6UL USB to UART has Level shifter is it require?

Question asked by ramesh t on Jan 18, 2017
Latest reply on Jan 26, 2017 by ramesh t

In IMX6UL reference design USB to UART circuit has 2 bit Level shifter and the notes mentioned "Level-Shifter to insure no IO backfeed".

 

Q1. What is mean by " Level-Shifter to insure no IO backfeed" ? 

Q2. Do we require Level shifter, If i connect UART Tx,Rx lines directly to IMX6UL processor pins what will happen?

 

As per my understanding USB to UART chip CP2102 has powered by USB cable at any time from different power source (Example : Laptop). so we need to makesure when the communication need to be happen and when its not so we are enable and disable 2bit level shifter accordingly. Is it correct?

 

Please see below snap-shot.

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