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

Yes, there is no code that would handle CASIC binary protocol for AT6558, only NMEA is used so
far for bangle2 and also ublox protocol for v1

Do you mean there is no specific code for either in the firmware. For B1 we send UBLOX commands via serial1.write() via a javascript app called gpssetup:

https://github.com/espruino/BangleApps/b­lob/master/apps/gpssetup/gpssetup.js

For Bangle 2 we should be able to do the same approach for but different bits and bytes as per the CASIC protocol. The quest we have is how to setup the AT6558 so that it accepts both CAS and CASIC instructions.

The problem we have at the moment is that the chip appears to be told not to listen or respond to CASIC instructions and the only way to comfigure it to respond is to send a CASIC instriction.

As for using Serial2 - instead of finding random pins for Serial1 it could also work to configure just >rx or tx, so do Serial1.setup with just tx: and then setup Serial2 with just rx: and hook into Serial2 >'data' event to get replies and still write to Serial1

This sounds promising. I would not have a lot of confidence in how to code that; but if someone can get the Bangle 2 AT6558 to respond to CASIC instructions (over Serial1,write(), or Serial2.write()) I'm reasonably confident I could figure out how to put the AT6558 into a power saving mode and reduce its battery drain and build a Bangle 2 version of gpssetup.