I've started running into a weird problem with my VCP's and Betaflight when I try to update firmware for my FC's.  Happens now on both F411's and F7 FC's.  Here's the details....

I plug the FC into my PC and it pops up in Device Manager correctly as a VCP and for my F411 FC it's on COM9.  It connects just fine to Betaflight and I can go in and make any changes I want and all is fine.  However, if I want to update firmware when I get to the point of clicking on the "Flash Firmware" button it starts to go through it's normal reboot sequence.  Then I get a message in red in BF that says "Rebooting to ROM Bootloader" followed by a "Failed to open serial port" message also in red.  When I go back into Device Manager instead of it showing up as a VCP it pops up under the USB Controllers section with a yellow flag stating "Unknown USB Device (Device Desciptor Request Failed)".  I've tried updating the VCP driver, choosing from my list and it fixes it back to where it will show up again as a VCP on COM9, but then does the same thing when I try to update the FC firmware.  Any ideas on what the issue is and how to fix it?  This just started recently so I'm not really sure what is going on.

Thanks

On some FCs you need to disconnect the USB cable then push and hold the boot button while inserting the USB cable in order to get it into "flashable" (boot) mode. When the FC is in boot mode, the button "Exit DFU mode" should light up. If that button is active instead of grayed out it means your FC is now in boot mode and can be flashed. Don't press the "Exit DFU mode" but press the "Flash firmware" instead. Then it should start flashing.

Disclaimer: I'm only talking from experience of my older Mamba F405 and F722 FCs. A similar sequence of events happen if I don't put them into boot mode with this method. I have others where I don't have to do this but these particular Mamba FCs need it. As far as I know one can use CLI commands to do the same but I have not bothered, boot button works for me so I stick with this method.

(14-Jul-2023, 09:40 PM)Mike C Wrote: On some FCs you need to disconnect the USB cable then push and hold the boot button while inserting the USB cable in order to get it into "flashable" (boot) mode. When the FC is in boot mode, the button "Exit DFU mode" should light up. If that button is active instead of grayed out it means your FC is now in boot mode and can be flashed. Don't press the "Exit DFU mode" but press the "Flash firmware" instead. Then it should start flashing.

Disclaimer: I'm only talking from experience of my older Mamba F405 and F722 FCs. A similar sequence of events happen if I don't put them into boot mode with this method. I have others where I don't have to do this but these particular Mamba FCs need it. As far as I know one can use CLI commands to do the same but I have not bothered, boot button works for me so I stick with this method.

Thanks Mike I'll give that a try but this FC (F411) has been updated previously.  Only reason I'm updating it again is to add the Spektrum protocol so it can be used with a different radio (for buddy boxing).  In addition at least one of my other F7 FC's is doing the exact same thing, yet a 3rd F7 FC works fine.  All are Skystars brand and the two F7's are the exact same model number.  I've been swapping around FC's to find one I can use with my Spektrum gear so I can buddybox with a friend.  The one F7 FC that does work may end up being the direction I have to go, but I hate pulling it out of the quad it's in now and there's no reason the others should work.

But that said I'll give it a shot and see what happens.  Will report back.  Thanks!

Well Mike that worked. It accepted the new firmware. Thanks a bunch! I'm still wondering why on my two F7 Pro's one works with pressing the boot button and the other doesn't. But at least I know now that it's a pretty easy work-around. Thanks again!

Good news, glad it helped. It took me a while to figure it out when it happened to me.