How to calibrate FOD fingerprint sensorOP:
https://t.me/MoZoiDStack/291. Install stock miui rom of your device region(Works fine on any stock miui but I find A9 MIUI 10 to work best especially for third party displays)
2.
Change your display settings to light mode(dont use dark mode) Go to settings-about phone-All specs/show all details- Repeatedly press kernel version until CIT menu launches
3. Click 3 dot menu button on top right in CIT menu, select 'advanced tools'
4. Select 'fod fingerprint calibration'
5. Press start, for Flesh Flat - Use an A4 paper to cover display and place thumb on top of fod over the paper and click start
6. For Black Flat - Use a black paper(preferably matte. Try to use any black material to cover. ) to cover lower half of display and press thumb over fod over the paper.
7. Now you may get Performance Chart Test Pass or fail. Either way, reboot and try add fingerprint and check if fod works. It will work fine even if you dont get performance chart pass
8. It is worthwhile to attempt a few times(Sometimes it shows success when you keep trying for 5-10 minutes) so that final status shows 'Performance Chart Test Pass' as fos will work even better then.
9. If your widevine status is L3,
follow this guide to restore widevine L1.10. Now take backup of this calibrated persist partition with widevine L1 from recovery. Keep this persist backup safely on a computer or any other device in case needed in future.
Notes:
-> Third party '5 point multi finger touch supporting' displays will work after fod calibration depending on ur luck. Some will work fine after calibration on OSS and miui roms, some will work only on miui roms/miui vendor roms while some will work well on miui 10 and work poorly on newer miui.