Hi,
What a chaotic schematic.
It will be hard for yourself to read....but for us even more.
Avoid crossings, keep distance, use GND symbols.
For the problem itself.
Just shifting bits out and in gives nonsense results. You need to synchronize both serial streams and you need some kind of frame sync.
(Example without framesync
ndombeginningWithoutaframesyncthebitstreamhasnostartnoendandnoordertheywillbeshiftedthroughtheoutputwithoutbytealignmentrandomen
"Space" is nothing. But you see how useful a "space" is as word sync, or a "." as sentence sync
And how useful special characters like "capital letters are"
There is no need to re invent the wheel. There are a lot of standard communication interfaces.
(Example without bit sync)
,$£:/7fuv/}ID&Uu♡■
.....and so on
--> total nonsense output
Read through UART, SPI, I2C.....
All are parallel to serial and back, all have dedicated ways to "sync" bytes and frames.
Klaus