Adding OpenWrt support for MikroTik Chateau LTE12

For Developers
1

Device: https://mikrotik.com/product/chateau_lte12

Current work can be found here: https://github.com/dchard/openwrt/commits/mikrotik_chateau_lte12

What works:

  • UART
  • Ethernet
  • LTE modem (Category 12.)

What does not work:

  • WIFI

For the WIFI part: MikroTik changed the BDF compression once again (to LZ77 this time). Hopefully @johnth can come up with a solution and update the platform driver soon.

As the Chateau LTE12 is a ROS7-only device (no simple way to downgrade to ROS6), the ability to build Routerboot7 compatible images is also needed. My branch already contains this part, based on the work of @johnth , tested all the way to ROS7.7 / RouterBOOT 7.7: both initramfs and sysupgrade images are working as expected, no need to downgrade or hack the device any other way.

Note: the modem is of course limited to Serial + MBIM by MikroTik, the AT command set is also somewhat limited. As the modem itself seems to be generic, hopefully it is possible to flash a generic firmware on it, which will provide QMI interface as well.

Once again, I want to thank @robimarko and @johnth for their hard work and help.

Update (2023-02-11): the modem can be flashed with generic FW, and QMI mode can be enabled with a simple AT command ( AT+QCFG="usbnet",0 ). In this mode, standrad modem and QMI interfaces are available, the modem stores this permanently.

Update (2023-02-26):

The Chateau 12LTE uses a special antenna configuration: there are 4 internal LTE antennas, plus 2 external SMA ports. These are connected on the main PCB to two pin control devices (RF switches). These pin control devices can be toggled via GPIO:

External antenna: None (equals to "auto" !! )

lte-ant-sw1:	activel_low=0	value=0
lte-ant-sw2:	activel_low=0	value=0

External antenna: Main

lte-ant-sw1:	activel_low=0	value=1
lte-ant-sw2:	activel_low=0	value=0

External antenna: Div

lte-ant-sw1:	activel_low=0	value=0
lte-ant-sw2:	activel_low=0	value=1

External antenna: Both

lte-ant-sw1:	activel_low=0	value=1
lte-ant-sw2:	activel_low=0	value=1

External antenna: Auto (equals to "none" !!!)

lte-ant-sw1:	activel_low=0	value=0
lte-ant-sw2:	activel_low=0	value=0

The modem stays in the same diversity mode (+QCFG: "diversity/config",4,0,0), as the manipulation only happens via GPIO.

I did not find out what "auto" mode means. When selected, no modem control nor GPIO change can be detected. Maybe it needs the manual run of "Antenna Scan" under ROS.

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