abijahkaj

Yes, the Quectel EC25-EUX supports VoLTE natively on the modem baseband, and from the board's perspective the audio path is identical: the modem handles the IMS/SIP registration and AMR codec internally and outputs standard 1.8V PCM digital audio to the RP2040 whether the call is over VoLTE or 2G/3G fallback.

I put that caveat in the README because VoLTE support in practice depends on carrier whitelisting and having the right carrier MBN profile loaded on the Quectel module (AT+QMBNCFG), not on the rest of the PCB. Here in Europe, 2G/3G is still up for a few more years, and major carriers have MBN profiles in the standard EC25-EUX firmware, so testing both VoLTE registration and CSFB fallback will be part of bring-up when the board lands.

yeah it's raw output from the router i'm coding without a trace smoothing pass yet, so it draws ugly jagged steps. looks bad to a human layout engineer, no argument there. either way it won't stop it from working, the electrons don't care how ugly the bend is at 2 MHz. just want to see if it boots when the jlcpcb parcel lands.

edit: idk why my comments are being [flagged], i've written to hn but the issue is apparently still there

Interesting read, is there a method that protects privacy? I think as you mentioned, changing the hashing algorithm won't fix the issue.