Sferalabs Iono Pi Max v2 3+ Lite User Manual page 30

NOTICE
Disconnecting an SD card from the Compute Module's SD interfaces when partitions from
the card are mounted at the operating system level, can result in file system and data
corruption. The Iono Pi Max matrix and the microcontroller don't check for card usage and
don't provide any safety mechanism to prevent improper disconnection of the SD cards.
The matrix is controlled by a few I/O lines of the Iono Pi Max SAME54 microcontroller.
These lines are managed using the microcontroller I2C control registers and the Iono Pi
Max kernel driver for Linux. The matrix has a hardware default configuration so that, when
at power-up all microcontroller lines are high-impedance, it has a stable configuration, with
SDX connected to SDA and SD1 not connected. When the microcontroller is reset, even if
the control lines change state, the matrix control logic will retain the current configuration.
SD MATRIX DEFAULT CONFIGURATION
With SDA used as the boot card, SDB can be connected to the SD1 interface, and used as
additional storage.
SD MATRIX BOOT FROM SDA AND SDB ENABLED FOR ADDITIONAL STORAGE
The SDX interface can be connected to SDB instead of SDA, so that boot will be done
from SDB.
30 Iono Pi Max User Guide