You can create a bootable microSD card image and use it to boot the ConnectCore MP25.

The ROM loader of the STM32MP25 can only boot from an SD card using SDMMC1 interface. On the ConnectCore MP25 the SDMMC1 interface is connected to the wireless chip, so wireless variants cannot boot from an SD card.

The microSD socket of the ConnectCore MP25 Development Kit is routed to SDMMC3 so this interface cannot be used to boot, either.

If booting from SD card is a desired feature of your product, you need:

  • a non-wireless variant of the ConnectCore MP25.

  • to connect a microSD socket to SDMMC1 lines on your carrier board.

Create a bootable microSD card

Build images suitable for microSD card

Digi Embedded Yocto builds images suitable for the eMMC of the ConnectCore MP25.

To build images that can boot from the microSD card, add the following to your project’s conf/local.conf file:

conf/local.conf
BOOTDEVICE_LABELS:append = " sdcard"
Note the required white space when appending a value to an array variable using the :append override syntax.

Build your image recipe, for instance:

$ source dey-setup-environment
$ bitbake dey-image-webkit

This creates additional image files in your project’s deploy directory that are required to generate the sdcard image.

Generate the image for the microSD card

Use the wic command in Digi Embedded Yocto to generate a microSD image. There is a wic kickstart file at meta-digi/meta-digi-arm/wic/ with a preconfigured layout for a 1 GB card. You can customize this template for your needs.

To generate the microSD card image, run the following command from your project’s directory where you have previously sourced the environment:

$ wic create ccmp2-<ram_size> -e <image-name>

where:

  • <ram_size> is the RAM memory size variant, such as 256MB, 512MB or 1GB.

  • <image-name> is the image name, such as dey-image-webkit.

You must have built this image in advance so the artifacts are available in the deploy directory.

This creates filenames in the form:

  • ccmp2-<ram_size>.wks-<timestamp>-mmcblk.direct

  • ccmp2-<ram_size>.wks-<timestamp>-mmcblk.direct.p1

  • ccmp2-<ram_size>.wks-<timestamp>-mmcblk.direct.p2

  • …​

The first file is a full image, whereas the p1, p2…​ are image files for each partition.

Refer to Boot from microSD card for instructions on programming the image on the microSD card and preparing your target to boot from it.