Regarding PGA bypass in ADS1262
I want to bypass the PGA to change the input signal range from +/-2.5 to 0/5 V range.


Look at the register map. it should allow you to by pass the pga.


  In the example, I have put #define VREF 5 but it shows the double the input voltage in serial window and when I put VREF 2.5, it shows regular input voltage.


Simple solution: divide the library's output by 2.

Right solution: the library likely doesn't support bipolar output. So re-write  your own.