How to read directly from Serial1? (baby steps into CASIC)

I am not saying about GPS chip input, I am about output, what GPS chip sends to Serial1 and how it is processed.
The code is in bool jswrap_banglejs_gps_character(char ch) in https://github.com/espruino/Espruino/blo­b/master/libs/banglejs/jswrap_bangle.c
it checks for a protocol, if it is NMEA or UBX it copyes data into ubloxMsg. Otherwise it just skips the data.
The way it check if it is UBX is in line 3690

    } else if (ch == 0xB5) {
      inComingUbloxProtocol = UBLOX_PROTOCOL_UBX;

That 0xB5 is specific to UBX, for CASIC it should be two bytes 0xBA 0xCE.
It also checks for consistency of NMEA at 3707-3719. I do not think it will pass whatever "unknown" binary data as NMEA. It will just skip it.