On a sunny day (Sat, 19 May 2018 20:17:28 -0400) it happened Dennis Lee Bieber
 wrote in :

>On Sat, 19 May 2018 18:54:26 GMT, Jan Panteltje 
>declaimed the following:
>
>
>>then MAYBE I would xor ptlrc output bytes with 0xff and same for input bytes
to force the invert ;-)
>
>        Unless you are bit-banging a GPIO, that won't work... 8-bit data is
>sent as 10+ bits by a UART.
>
>1 start bit
>8 data bits
>1+ stop bit (some devices required up to two bit times before they could
>handle a new start bit.
>
>        You'd be inverting the 8 data bits, but not the start/stop bits. Stop
>bits are whatever the protocol considers as an idle state (pull up or pull
>down, so when the UART is not doing anything, the line shows a stop bit.
>Start bit is the inverse of a stop bit -- basically a forced level
>transition to wake up the receiver UART, since the first data bit could be
>the same state as a stop bit.

You are absolutely right.

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