2.7.2 Unused Parallel Camera Interface Signal Termination
All unused parallel camera input signals can be left unconnected if the interface is disabled in
software. It depends on the module whether the signals can be used as GPIO when they are not
used as a camera interface.
2.8 SD/MMC/SDIO
The Colibri module form factor features one SD/MMC interface as a standard interface. The
interface provides up to 4 data bits that can be used for interfacing SD, MMC cards, and SDIO
interface peripherals. Depending on the module, there might be additional data signals to get an
8bit interface. MMCplus cards and eMMC memory chips use this bit width. The additional data bits
are not intended to be compatible between different Colibri modules.
The SD cards know different bus speed modes. The required signal voltage depends on the bus
speed mode. For example, the SDR104 mode requires 1.8V signaling. In the Colibri module
definition, all GPIO capable interfaces, including the SD/MMC/SDIO, are defined for 3.3V. Some
Colibri modules might be capable of switching the voltages of the SD card interface pins to a 1.8V,
but it is not mandatory. Read the related datasheet of the Colibri module.
Even if the bus speed mode requires a signaling voltage of 1.8V, the supply of the card itself is still
3.3V. Pay attention to the SD card signal pull-up resistors on the carrier board. If the carrier board
should support the 1.8V mode, the pull-up resistors' voltage also needs to be switchable. Some
Colibri modules might allow removing the pull-up resistors on the carrier board and using the
internal ones only. In this case, this is the preferred solution. Even if the external pull-up resistors
are not mandatory, we recommend adding not-assembled pull-up resistors to the 3.3V rail to be
compatible with future modules.
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