Hi guys maybe you will have some smart ideas what to check,
i have mounted the f303 board on a scrap xzmr, however the issue is that everytime i boot the fc (usb/battery alike) it enters boot mode...
i've uploaded new software, and after upload i can connect via betaflight config... issue is when i reboot... im again in boot mode...

what i have tested so far:
- uploaded newest betaflight 3.0
- uploaded betafligh 2.7
- checked with multimeter the "boot" buttton - when pressed there is a connection, when not no connection - so it works

at the moment i have 2 ideas:
- maybe one of ESC is sending some "stupid" signal
- board is crap (this piece)

All the best and formally hello as this is first post after few months of stalking
Grzesiek

Why do you think it's in bootloader mode when start up? have you also tried "erase all settings" while flashing firmware?

Only blue led is showing up, in normal boot there is also activity led (red) blinking.

i've done full chip erase, and im able to reflash it as many times as i want. still until first reset... then im again in "blue" led only.

this sounds exactly like my dead Naze board.
Same I could flash a million times if I want, but it just stuck in bootloader mode. It was like that after some big soldering job, I reckon I burned something. Eventually I had to replace it.

Let the board rest for some time... today connected with usb... correct boot...
now "only" blue light is when i connect battery...

after short troubleshooting with Konrad.

he found that im a lazy person ... and i've connected rx/tx aiming for osd to uart 1 which is shared with usb... and when battery was connected 12v flew to vtx, 5v to osd... and we have a winner...

at the moment fc is booting all right every time.

(27-Aug-2016, 07:07 PM)Grisha0 Wrote: Let the board rest for some time... today connected with usb... correct boot...
now "only" blue light is when i connect battery...

after short troubleshooting with Konrad.

he found that im a lazy person ... and i've connected rx/tx aiming for osd to uart 1 which is shared with usb... and when battery was connected 12v flew to vtx, 5v to osd... and we have a winner...

at the moment fc is booting all right every time.

hi  Grisha0 , i have almost the same problem , i  fitted a X_RACER v 3.1  to my quad running betaflight 3.0  yesterday  and for the first couple of goes it started fine and flew but after a few batteries every time i powered it up  a single blue light came on  and it did not make the right start up sounds , but if i plug in a powered usb first then plug in the battery  it powers up correctly  and will fly . i have no OSD . If you have any ideas i would be greatfull for some advice regards  jack