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intelfx
Core Memory
Posts: 25
Registered: ‎09-15-2016
Location: RU
Views: 431
Message 1 of 3

Getting Sierra EM7455 (and similar) to work on X1C6

To avoid derailing other Fibocom vs. Linux threads, I'm gonna post this here:

 

It appears possible to make Sierra Wireless EM7455 to work with X1C6 (confirmed on firmware versions 1.31 and 1.34) with a simple modem configuration change.

 

Caveat emptor:

 

  1. This is an unintended effect and may change in future firmware versions.
  2. This effect is presumed to be based on a race condition and therefore may break at any time.

 

 

Guide:

 

  1. Boot to Linux without a modem in place.
  2. S3 suspend your laptop. (Make sure it's configured to use S3!)
  3. Hot-plug the EM7455 modem.
  4. Resume the laptop. Whitelists are not consulted on S3 resume.
  5. Wait for the modem to fully initialize. If needed, change USB composition and/or update the modem firmware so that the AT port is available.
  6. Attach with a serial terminal emulator (e. g. picocom) to /dev/ttyUSB2 (assuming you have no other USB-serial converters installed).
  7. Verify that the modem responds and enable command echo (if echo is disabled, you won't see this command as you type it):
    ATE1
    OK
  8. Unlock engineering commands:
    AT!ENTERCND="A710"
    OK
  9. Check current modem customization settings:
    AT!CUSTOM?
    !CUSTOM: 
                 GPSENABLE          0x01
                 IPV6ENABLE         0x01
                 SIMLPM             0x01
                 FASTENUMEN         0x01
                 SINGLEAPNSWITCH    0x01
    
    
    OK
  10. Reconfigure fast enumeration:
    Option 1. Enable fast enumeration for warm boots only:
    AT!CUSTOM="FASTENUMEN",2
    OK
    Option 2. Disable fast enumeration altogether:
    AT!CUSTOM="FASTENUMEN",0
    OK
  11. Verify:
    AT!CUSTOM?
    !CUSTOM: 
                 GPSENABLE          0x01
                 GPSSEL             0x01
                 IPV6ENABLE         0x01
                 SIMLPM             0x01
                 FASTENUMEN         0x02
                 SINGLEAPNSWITCH    0x01
  12. Reset the modem and wait for it to reappear (to ensure that the new settings are saved):
    AT!RESET
    OK
    (the terminal will close itself shortly)
  13. Test: reboot, soft power-off, hard power-off (pull out the battery or push the RESET pinhole button).

 

Explanation:

 

can be found in any of the threads I've derailed Smiley Happy

duvh93
Paper Tape
Posts: 3
Registered: ‎10-22-2018
Location: IT
Views: 169
Message 2 of 3

Re: Getting Sierra EM7455 (and similar) to work on X1C6

Thanks for this walkthrough...

 

I still cannot connect using the EM7455B.

 

AT!PCINFO?
State: Low Power Mode
LPM voters - Temp:0, Volt:0, User:0, W_DISABLE:1, IMSWITCH:0, BIOS:0, LWM2M:0, OMADM:0, FOTA:0
LPM persistence - None
!CUSTOM: 
             GPSENABLE		0x04
             GPIOSARENABLE	0x01
             GPSSEL		0x01
             IPV6ENABLE		0x01
             SIMLPM		0x01
             USBSERIALENABLE	0x01
             FASTENUMEN		0x02
             SINGLEAPNSWITCH	0x01
AT+GMR
SWI9X30C_02.30.01.01 r7792 CARMD-EV-FRMWR2 2018/07/13 02:24:52

I am wondering why is W_DISABLE=1...should I put tape on the pin?

 

AT!PCOFFEN=2

 Is enough to ignore the W_DISABLE pin level

intelfx
Core Memory
Posts: 25
Registered: ‎09-15-2016
Location: RU
Views: 143
Message 3 of 3

Re: Getting Sierra EM7455 (and similar) to work on X1C6

Yes.  Thank you for this addition; I've forgot to mention this problem.

 

Explanation to all future readers: basically, by following this method, firmware is made to "not see" the modem. As such, it will force assert the W_DISABLE pin on the M.2 slot, and will not export ACPI methods needed to control this pin from the OS (that's why there is no usual WWAN rfkill). Thus, the modem is forced into "airplane mode".

 

Thankfully, EM7455 can be made to ignore the W_DISABLE pin via another special AT command (which is also password-protected):

 

AT!ENTERCND="A710"
OK

AT!PCOFFEN=2
OK

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