> For the complete documentation index, see [llms.txt](https://wiki.cbunmanned.com/wiki/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://wiki.cbunmanned.com/wiki/products-eol/cbu-cm405-fc-eol/micro-sd-card.md).

# Micro SD Card

On the bottom side of the board are 2 micro SD card slots. 

(Red) Is connected to the STM32F405 for flight data logging/LUA storage.

(Blue) Is used when a CM4 "Lite" model is used, and should be flashed with the desired OS. If using a CM4 with EMMC ensure there is no SD card fitted.

<figure><img src="https://1886089318-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2FolH18CdGEWKpuo9G8NHx%2Fuploads%2FE22HudtIo5bfF8riVLCu%2Fimage.png?alt=media&amp;token=b6d990c0-4e16-449e-a3ec-f4a060ac56e4" alt=""><figcaption></figcaption></figure>