Enabling the RTC battery

Before you start up the Mainboard, make sure that the real-time clock battery is turned on. It is initially deactivated to save energy. To change this, use a small screwdriver to set the switch to the correct position. Also, ensure that all other switches are set to ‘OFF.’

How to enable the RTC battery

Forcing the BMC in bootloader mode

You can put the BMC (not the CM) into bootloader mode by setting the bootloader switch to “ON” and doing a power cycle (a restart is not sufficient!).

Integrity of the RAID

The operating system runs on two SD cards in so called RAID 1 (mirroring) mode.
If one fails, the system continues to function.

There may be a degraded warning if:

  • The two disks are not synced or syncing
  • There is only one disk
  • One disk is faulty

On first boot it takes 2-3 hours to complete the sync.

If the status has not changed after 3 hours, you should download the latest backup immediately (or create one now).
Do not reboot the system unless you found the issue!


You should investigate which SD card is faulty. Login via console and check:

cat /proc/mdstat


If the disks are syncing a progess will be shown.
You can see the expected time to finish in the output.
If you restart the system during synchronization, it will start from the beginning.

Personalities : [raid0] [raid1] 
md42 : active raid1 mmcblk1p2[2] mmcblk0p2[0]
      20832768 blocks [2/1] [U_]
      [>....................]  recovery =  0.9% (198656/20832768) finish=81.2min speed=4234K/sec

Faulty SD card

Personalities : [raid0] [raid1] 
md42 : active raid1 mmcblk1p2[2](F) mmcblk0p2[0]
      20832768 blocks [2/1] [U_]

The “(F)” indicates the failed SD card.
In the above example “mmcblk1p2” is faulty which is SD card 1 on the Mainboard.
“mmcblk0p2” is SD card 0 on the Mainboard.

Integrity of the file system

The filesystem is checked for errors once a week (full metadata+data check).
If the status is degraded, you should download the latest backup immediately (or create one now).

Real-time clock (RTC) battery

The device contains an RTC which is powered by a CR2023 battery.
It is used to keep time during periods without power supply.
If the battery level falls below ~2.8 V, the battery should be replaced, otherwise the time will be lost during the power supply interruption.

Flash sdcards

See Maintenance / Flash SD cards

Replacing the SD card

See Maintenance / Flash SD cards

RAID limitations

Although the RAID ensures that the system continues to run, it has some limitations due to the Compute Module:

  • The system only boots from SD card 0, if it is defective, it may not boot (create a backup and download it before rebooting!!).
  • If you insert SD card 1 into SD card slot 0, the system will not boot because the boot partition is not formatted (will be fixed in the future)

How to install the Mainboard on a DIN rail [TODO]

Add instructions how to mount the Mainboard

How to connect using the serial port [TODO]

LED description

Color Label Led On LED off LED blinking LED blinking fast
Red BMC warning error appeared / reset
Green BMC activity BMC off BMC active BMC shutting down CM
Green 3V3 voltage ok
Yellow CM active CM starting / in bootloader mode CM off CM active
Yellow (USB) Serial console Serial console connected No cable connected / Bootloader mode