# How to daisy chain SWD Debug port

I have multiple mcu's that are configured to communicate with bus topology. I have 10 pins (4 of them is occupied by now)

I need to debug (update firmware online, etc) all of these mcu's. I read this article but I didn't understand how to achieve the goal.

Question: How can I daisy chain these mcu's?

MCU: STM32F407VG

Debug protocol: SWD

• Your development tools need to support it. – Leon Heller Mar 8 '14 at 12:24
• I need the algorithm, I can build the development tool. – ceremcem Mar 8 '14 at 16:26
• I think that you need to license that from ARM. – Leon Heller Mar 8 '14 at 17:06

Note that you might want to separate a firmware update from your debugging scenario. Firmware updates can be done in multiple ways using a bootloader, so SWD or JTAG is not required in this case.