STM32L not booting when ST LINK is connected to a powered down USB hub?

[ZurnOmniflo]

Hi everyone,

I'm building a unit that requires sealing the ST LINK in with my STM32L so that I can update the firmware without accessing any of the hardware. I also have a limited number of output ports available to me, so I'm forced to "multiplex" a number of my USB devices (the ST LINK, which is left connected to the STM32L, as well as a few other, unrelated devices) - through a hub and output them all through as single USB connection. This works fine, except for one problem: my STM32L only runs when the USB hub is powered, which occurs when its connected to a computer. If I unplug the ST LINK from the hub but leave it connected to the STM32L it runs fine.

So my question is: is there any way to configure the ST LINK and/or STM32L to ignore the ST LINK VBUS status? Again, it works when the ST LINK is connected to the STM32L on one end and nothing on the other, or when its connected to the STM32L and the powered hub, but not when it's connected to STM32L and the unpowered hub.

Leaving the hub powered isn't an option as it interferes with the functionality of other components in my circuit.

Really, any advice about troubleshooting this would be greatly appreciated.

[Uwe Bonnes]

Are you talking of a board with on-board STLINK or a custom board with external stlink? Did you have a the power option of the cuttable STLINK on a Nucleo? Does perhaps STlinkV3 -Set or Mini offer more options?

[ZurnOmniflo]

Great questions. I should clarify: this is a custom board with an external ST LINK V2 connected to it. It's actually a specially designed board that I'm repurposing rather than a proprietary one, so no Nucleo. Switching to an STLINK-V3 seems risky, as it may be a lot of work for no results (I'm guessing - I'm VERY new to the world of embedded).

[ZurnOmniflo · Accepted solution]

Found a solution for this here