The SpO2 module I use is of none parity.

I wonder the PIC have the problem to read the bytes if the bytes are sent into PIC in endless stream. I tried to send only 5 bytes, 10 bytes and 15 bytes data in SpO2 module's data format and the PIC can process well using the code I wrote.

Then I tried to let PIC sent out each byte it read in from a endless bytes stream. The output of the PIC is different from the data it read in.