Unequipped filter parts on Olimexino-STM32 Rev.B

[Yogybear]

Hi,

I'm using several Olimexino-STM32 Rev.B boards in an emp noisy environment, attached at the same parts, but one of it breaks sometimes the serial communication over USB. I'm pretty sure the cause of this problem is the emp noise. Since I'm using the Olimexino-STM32 I wonder about some empty pads on the board. Now I'm curious if equipping of some empty pads or changing existing parts might help to filter the noise. If yes, which values on which parts would you recommend?

Thanks a lot in advance.

Kind regards,
Yogybear

[Yogybear]

Hi,

I looked closer on the schematic of the Olimexino-STM32 Rev.B and found an unequipped part (U6) which I've never seen before:



Could someone please identify this part? It would be interesting for me if this part works like a noise filter.

Thank you in advance.

Kind regards,
Yogybear

[LubOlimex]

Hey yogybear,

U6 is for USB protection, it might protect both the computer (if the device tries to run some over-voltage towards it) or the USB device (if the computer tries those).

Best regards,
Lub/OLIMEX

[macbeth]

... digging up this old thread...
Would you mind telling us which part and footprint U6 is?

I just had 4 Olimexino STM32 that died after being plugged into a PC. I have no idea why.
Could a ground loop between PC-USB-ground and an external power supply kill the STM?

[macbeth]

Ok, I found U6 in the eagle files. USBLC6-2P6.

I'd still like to know if potential differences between USB-Ground and board-Ground can fry the STM. Any suggestions?

[JohnS]

Are the grounds not tied together?

If not, why not?

John

[LubOlimex]

Hey,

This is interesting.

What are the hardware connection that you established? Do you use normal USB cable or some specific cable? By the way how did you determine that the boards died? Nothing shows in the Windows Device Manager?

I'd still like to know if potential differences between USB-Ground and board-Ground can fry the STM. Any suggestions?

I haven't seen such a case, we never had such a problem during testing nor customer complaint. However, it is possible explanation for the problem.

As you noticed the two grounds are connected together via the C7 capacitor.I believe these faults might be caused by C7 - try to remove it.

Best regards,
Lub/OLIMEX