Dual Microsd Cards Routing (Strato Pi Cm Duo Only); Xsdpn - Power Up Routing - Sferalabs Strato Pi Base Advanced Configuration Manual

Dual microSD cards routing (Strato Pi CM Duo only)

Strato Pi CM Duo allows the two SD interfaces of the Raspberry Pi Compute Module Lite
to be routed to two external microSD cards.
The primary SD interface of the Raspberry Pi Compute Module Lite is called SDX. This
interface is used for the SD card where the boot partition must be found to boot the
system, and must remain connected to SD card at all times while the OS is running.
A secondary SD interface is called SD1. This interface can be used to connect a second
SD card where other, non boot partitions, can be present.
The two microSD slots of Strato Pi CM Duo are called SDA and SDB.
Strato Pi CM Duo has a high speed 2x2 hardware matrix, that can be configured to
independently enable the data lines to and from SDX and SD1, and to define which SD
slot is routed to SDX and SD1.
The default configuration is to have SDX enabled and routed to SDA, and SD1 disabled.
This is the firmware factory configuration, and is also forced in hardware when the MCU
pins are high impedance.
Control of the 2x2 matrix is based on three pins of the MCU:
MCU pin
RA5
RC0
RA4
These pins can be directly controlled, or configured to be set to the desired state during
the next power cycle, using dedicated commands. It is also possible to configure the
watchdog to switch the SDX interface to the other SD card slot if a watchdog timeout
occurs.

XSDPn - Power up routing

Set the SDX/SD1 interfaces routing at power up.
Command Description
XSDPA set SDA to SDX bus, SDB to SD1 (RA4 = L) at power up (factory
default)
XSDPB set SDA to SD1 bus, SDB to SDX (RA4 = H) at power up
XSDP? return SDA/SDB routing mode set for next power up
12
High
SDX interface enabled
(default)
SD1 interface enabled
SDX to SDB
SD1 to SDA
Low
SDX interface disabled
SD1 interface disabled
(default)
SDX to SDA
SD1 to SDB
(default)
Reply
XSDPA
XSDPB
XSDPn
Strato Pi Logic Controller