5 replies to this topic

[Frode]

Hi, 

I'm trying to figure out if I've just bricked my second NetDuino Plus 2.

 

The last time it ran it got an exception on a new piece of code I just wrote. After that it doesn't boot properly anymore.

 

When I plug in the USB cable it immediately beings emitting a high-pitched sound, and the ARM chip starts getting hot. In a matter of 5-10 seconds it's too hot to touch.

 

I've tried holding in the onboard switch while plugging in the USB to force it into bootloader mode, but nothing happens. It doesn't show up in the DFU Tester or in MFDeploy.

 

Is there anything else I can try to breathe life back into it?

[cys]

If I had to speculate, I would suggest that there was some kind of esd/overvoltage event. Most likely it's toast.

[Chris Walker]

Hi Frode, What do you have plugged into your board? How are you powering the board? The DC-DC switching will effectively act as a speaker if you're drawing vast amount of power, short circuiting, etc. There's some protection circuitry in there to help protect the board from casual short circuiting events... And a USB fuse to limit current to 500mA through the MicroUSB port. If the ARM micro is heating up hot, then it's most likely that the chip was electrically damaged and may be drawing all the power available on the board. On your first board...were you able to erase and reflash it? Chris

[Frode]

Hi guys, 

there is nothing connected to the board (except the mini-usb cable). Just before it stopped working I was using two PWM pins to control two ESC's which in turn control four DC motors. The ESC's have a 13V power supply as well. Maybe I touched that adapter and the board at the same time, I don't know.

 

I tried powering the board with a 7.5V adapter instead of the USB, but it still misbehaves. The PWR led blinks once, and the onboard led is sort of half-dimmed. The Act doesn't light at all.

 

Other times when the board has acted up I've been abloe to erase and reflash it, but now it doesn't want to go into bootloader mode.

[Chris Walker]

Hi Frode, If the ARM micro is heating up hot, then it's most likely that the chip was electrically damaged and may be drawing all the power available on the board. Is it possible that the ESC's weren't trying to draw power from the micro? Or delivered power in reverse somehow? 13V is a lot of voltage for the STM32's digital pins. If you were powering via MicroUSB, then the 500mA fuse should help stop power delivery if more than 500mA is pulled by the DC-DC switch. If feeding power by the AC adapter, then the 5V LDO helps avoid short circuits but the 3.3V DC-DC switch has to take the brunt of over-current draw. My guess is that the digital header pins (which are connected directly to the microcontroller pins) might have been accidentally fed 13V during wiring of the ESCs or a higher voltage source with common ground might have accidentally touched the micro. I've spent thousands of hours with Netduinos and I may have done that once myself. In any case...burned up microcontrollers are no fun at all Chris

[Frode]

Thanks, I don't see exactly how it could have happened, since I didn't do any rewireing when it failed. I was just writing code to hook up an eventhandler for the onboard switch to use it to change directions of the motors. 

I powered up the ESC's now with the external 13V adapter, and measured the voltage on the signal lines (which is the I send a PWM signal to from the Netduino), but it only had about 0.1V, so I don't think the D3 or D5 ports got burned that way.

 

I've ordered a new NetDuino Plus 2 now, so I'll just have to be more careful with that one. 

 

Thanks for your responses