[General Topics] skaldamramra:
Hi everyone

I am going to write some information about a problem I had with my bison 2020 and solution I came up with for anyone that might face the same situation in the future.

Bison cannot call or receive calls (altough sms and data works fine).

It is possible that you somehow deleted/formatted modem database. So now when your phone tries to make connection to nearest cell, it doesn't know what signal strength/angle/etc. to use. It is only affecting calls because in most countries SMS/data and other things are handled as digital stream nowdays.

For mediatek chipsets you need Modem meta application ( http://www.mediafire.com/file/u111ixvky9b7hec/Modem_META_ver_10.1844.0.01.zip ). This can access your modem on several mediatek chipsets (I tested on umidigi bison 2020).

-You need to have standard USB VCOM drivers installed (so if you are able to work with SP flash tool or SN writer, you'll be fine with this tool as well)

-Run meta.exe (with phone unplugged and turned off)

-Platform type = Smart phone, Com port = USB COM

-Click connect , connect your phone turned off (same as when using SP Flash tool/ SN Writer)

-Len meta go throught connection process, wait for "Connected" to appear in lower left corner

-Search bar in upper right -> write UpdateParameter Tool then click on result

-Meta asks to Load DB file -> Select "From Target"

-Now a UpdateParameter window appear. I strongly recommend to use "export" button first. This will dump and preserve your current modem settings in case something go wrong. Click "export", name output file and save it somewhere on your PC.

-If you open file you just exported in notepad, you will see your current modem dump. If if looks barren with lots of zeroes all around, so like this:

[DCS1800 EPSK inter slot ramp]

EPSK EPSK inter slot ramp = 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0

EPSK GMSK inter slot ramp = 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0

GMSK EPSK inter slot ramp = 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0

GMSK GMSK inter slot ramp = 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0

[DCS1800 level, ramp]

APC dc offset = 0

APC lowest power = 0

Battery compensate, high voltage, high temperature = 0.00000

Battery compensate, high voltage, low temperature = 0.00000

Battery compensate, high voltage, mid temperature = 0.00000

Battery compensate, low voltage, high temperature = 0.00000

Battery compensate, low voltage, low temperature = 0.00000

Battery compensate, low voltage, mid temperature = 0.00000

Battery compensate, mid voltage, high temperature = 0.00000

Battery compensate, mid voltage, low temperature = 0.00000

Battery compensate, mid voltage, mid temperature = 0.00000

Low APC dc offset = 0

and so on...

Then you can see your problem (missing modem data, so no useful settings are loaded for any working frequency and your modem won't know how to connect to mobile cells in your vicinity (no IMEI or any other code change will resolve this.)

So how you can repair your phone? You need correct modem settings. Umigidi certainly has them, because obviously they are flashing them in factory. After some search i found modem settings for Umidigi A9 which has the same RF Chip ID (RF_ID_MT6177) that my bison used for testing has. So I opened A9 settings and copy-paste all sections with identical headers to my broken bison modem dump. So for example if my broken dump from bison has a section called

[GSM850 EPSK inter slot ramp]

EPSK EPSK inter slot ramp = 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0

EPSK GMSK inter slot ramp = 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0

GMSK EPSK inter slot ramp = 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0

GMSK GMSK inter slot ramp = 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0

RF Chip ID = RF_ID_MT6177

Then I replaced it with section from A9

[GSM850 EPSK inter slot ramp]

EPSK EPSK inter slot ramp = 255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255

EPSK GMSK inter slot ramp = 255,255,255,255,0,0,0,0,0,10,25,50,100,180,228,255

GMSK EPSK inter slot ramp = 255,232,160,50,25,0,0,0,0,0,0,0,255,255,255,255

GMSK GMSK inter slot ramp = 255,228,180,100,50,25,10,0,0,10,25,50,100,180,228,255

RF Chip ID = RF_ID_MT6177

Let me remind you that you are doing this on your own risk, I strongly don't recommend copy-pasting values for different RF Chip IDs as different hardware may react differently to same setting and you cas damage your hardware. If you can, try to obtain your original modem settings from Umidigi.

Anyway, when you will have a functional modem settings ready, then you can flash them with meta.

-In the updateParameter tool we talked about before press "import", locate correct modem settings ini file on your PC a click "open"

-In the updateParameter tool click on "Write" and let meta write new settings to your phone

-When you see DONE: write data to target then you are finished. Unplug your phone a power it on. Everything should work correctly now.

If you still can't make calls then repeat process and make sure you've done everything correctly. It is possible that you flashed incompatible modem settings and need to find/make another.

Hope this helps all of you that are struggling with calling/receiving calls, because it is usually not the IMEI fault.

Reference Umidigi A9 pro modem settings - https://www.mediafire.com/file/uoz066itfqyljd4/A9PRO64GB.ini/file

My modified Umidigi Bison 2020 (6GB/128GB) modem setting that works on my Bison -http://www.mediafire.com/file/67zvd78rppndc8g/Bison_fix.ini

Update 9.4.2022 - I searched russian 4pda and they got modem settings for A9 Pro 6/128GB as well, adding link for reference https://www.mediafire.com/file/7c8rsi2c579w6jl/A9_PRO_6_128.ini/file