I have a newbie question. I tried to flash PX4 onto my crazyflie 2, I tried master, stable and beta (via QGroundControl or manually), all of these finished flashing (erase, program, verify), but CF wasn’t able to connect with QGC. It seems the flie is still in boot loading mode, QGC firmware tab detected the flie and suggest flashing:
Found device: PX4 FMU V2
connected to boot loader:
version: 5
Board ID: 12
Flash size: 1032192
I tried using the latest PX4 firmware, master, stable, and beta, none were able to connect after flashing.
On the other hand, I had a older piece of code “50ecee9d” Wed Jun 7 14:19:57 2017 that I can flash and connect with QGC, calibrate and so on.
Is this a known issue? Or did I miss something obvious?
@ageofish: Unfortunately I am not familiar with the Crazyflie 2.0, so some of my comments may not be applicable.
Are you sure your firmware upload was successful? If the firmware flashing did not finalise successfully, then the vehicle will remain in the bootloader mode (this is the standard behaviour of the bootloader if the upload was not successful).
Can you try and power the CrazyFlie separately (not with the USB cable) and see if the vehicle boots correctly. If this is the case, then it could be that when you powered it via the USB, the bootloader received some data on the USB that it considered to be valid, so it remains in the bootloader waiting for a firmware upload.
@ksschwabe thanks for replying…
The only proof of firmware upload success was the print out from flashing:
Erase complete
Program complete…
Verifying program…
Verify complete
Upgrade complete
If I power it up with battery, the green M1 light flashes (I think this indicates it’s in bootloader mode) for about 5 seconds.
If I plug in the USB when it’s flashing, QGroundControl will recognize the board and ask for upgrade, after the 5 second, it won’t connect or recognize CF.
@ageofish: It seems that your bootloader is working correctly and that you are able to flash firmware. If you say that it works when you downgrade to an older firmware, then it could be that there is some hardfault that has been introduced in the newer firmware.
Do you have access NSH console on the vehicle?
@ksschwabe, I asked the same question here: https://github.com/PX4/Firmware/issues/7624 and it seems dennisss has found where the problem is.
By the way, I can use QGC to access the NSH console when connected through USB, but not able to link to it when using the Crazyflie radio PA. Is this by design?
@ageofish: I am glad that you have managed to get to the bottom of the problem.
Unfortunately I have no experience with the Crazyflie, so I can only speculate… When connected via the radio, do you see data coming through in QGC. If not, then the problem is the connection between QGC and the Crazyflie. If you do get data through to QGC, then problem could be that the Mavlink shell wasn’t started.
I don’t use QGC, so I am unable to help you further with that. 
