In order to make this good phone great it needed two things:
1. VoLTE - that was added by the MM update
2. For US, T-Mobile needs also the LTE band 12. This is VERY close to B17 (both 700MHz bands, blocks "a,b" for 12 and "b" for 17), so enabling it in the radio might work (analog side allowing the extra band).
What I did for now. I downloaded a package from around here that contains the Qualcom diag software QPST and QXDM Pro. Search for them.
1. Enable USB Debugging on the phone. Plug in the phone and the diag drivers will install (I'm on Windows 10 here, I have installed previously the drivers from Asus). Now the diag mode can be enabled in ADB:
ADB shell (should connect to the phone)
setprop sys.usb.config diag,adb
2. After drivers install automatically (Windows 10), the QPST server recognize the phone on COM4
3. Now the QXDM Pro can read the NV values. I am interested in LTE part - add B12. I recalculated the values for existing ones against the published specs and they matched, so the software that calculate the values seemed to work correctly. For LTE bands 1,2,3,4,5,7,8,17,20 the NV 06828 value is 590047. IMO nothing else need to change in the other sections of NV.
4. Calculated the new value with the band 12 added. New value that resulted is 592095. Insert the value in the field, pressed "Write". Then pressed "Read" and the value was there. Cool, now is time to reboot the phone, to activate the new value.
5. Phone rebooted, nothing different. Read again the NV 06828 and... it's back to the original value! Seems that at reboot the firmware rewrites that value. Not cool!!!
Now I am not sure if the drivers prevent the actual write to the chip or if the firmware re-writes at boot time the OE values.
Luk1337 stated that "/system/bin/rmt_storage overwrites the settings".
Maybe someone can patch that?
