Bolt not connecting after crash

[Bhanu]

Hello

We have built a quadrotor(picture attached) with crazyflie bolt. Initially, it worked perfectly, once it crashed to the wall, it stopped responding.
It does not connect to the radio but connects to the app via Bluetooth. When I power on only one blue light( right back) is on. What does this mean and how to solve the issue? I tried to use recovery with crazyflie client but the radio does not connect.

Did anyone had a similar issue?

Please help.
Thank you

[tobias]

It seems like the STM32F405 MCU does not start. Can you enter bootloader mode by holding the button until blue M2 LED start to blink? Blue M3 LED should start to blink then as well.

Any difference if you power the Bolt only using USB?

Visually check for any physically damaged component. Also use your nose to check if the board smells burnt.

[Bhanu]

I can enter bootloader mode, only the M2 light is blinking. M3 LED is still off. Radio does not detect the bolt.

No difference if I power the bolt using USB, the PC also does not detect it. Visually no physical damage and the board does not smell burnt but it is getting really hot when plugged in.

[tobias]

Do you have a multi-meter so you can check the VCC 3V voltage on the expansion connector (pin 1 on left side)?

Can you feel what component is getting hot?

How are you powering the ESCs. The motors look a bit big to be powered though the Bolt which can handle max ~8A per ESC. Are you using a 3 cell battery?

[Bhanu]

Yes, the VCC 3V on the multimeter shows 0.76V on one bolt and 2.99 on the second one.

One the first bolt is hot all over the board and the second one is just near the IC.

ESCs are powered through bolt and I checked the spec sheet of motors, each motor does not draw more than 8A current. Yes, I am using a 3s lipo battery.

[tobias]

Bolt nr1 has a short somewhere then.

Bolt nr2 will not enter bootloader mode either?

[Bhanu]

We flew the drone with both the bolts, it might have a short in the crash, is there a fix?

Bolt nr2 is also not responding nor entering the bootloader mode, just M2 LED blinking, M3 LED is off.

[tobias]

It is a bit strange that both bolt died in a crash, it sounds a bit too unlucky.

For Bolt nr2 can you point out exactly what component gets hot?

[Bhanu]

Just the IC on the bottom

[tobias]

The bottom big IC (STM32F405) will get a bit warm but should not get hot. My guess is that both STM32F405 has broken for some unknown reason. I think it would be to hard for you to investigate. Could you send an email to support (at) bitcraze.io so we can arrange replacements and get the boards back so we can investigate.

I'm a bit worried though that there is something with your setup that the Bolt can't handle. A sort of week point is if the signal wire gets shorted to the battery supply in any of the ESC connectors. This could damage the STM32F405 as the pin would get ~11V on that pin on 3 cell battery. Is this a realistic case?