> 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="/files/kIGdbzaOCQ4C6e1pF68i" alt=""><figcaption></figcaption></figure>


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