> 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="/files/JnQnHa2VBDYKwFBx5Otx" alt=""><figcaption></figcaption></figure>