> 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-usb.md).

# Micro USB

There are 2 micro USB ports on the board. 

(Red) is connected to the STM32F405 and used to flash firmware in DFU mode and as a telemetry connection under normal use.

(Purple) is used solely to flash the EMMC on the CM4. It is only connected when the DIP switch (1) is set to "ON".

<figure><img src="https://1886089318-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2FolH18CdGEWKpuo9G8NHx%2Fuploads%2FRjhIMtZ30zQpzYJ1tBQc%2Fimage.png?alt=media&amp;token=bb4b8a19-59b7-472f-94f2-78dbce6ff203" alt=""><figcaption></figcaption></figure>