Beware cheap (build) STM32F4 Dicovery boards!

Testing/Troubleshooting
1

I received my first F4 Discovery board from an Chinese ebay seller along with some excellent value LEDs and an LCD display this week.

The F4 was able to be flashed with it’s booloader through the ST link as per TK’s instructions.

It was when I attached the target USB connection that didn’t work, that I spent quite a few hours to sort things out. I found:

  • various short circuits under CN5 (the target USB port)
  • USB data line short circuited by a solder bridge.
  • SMD capacitor open circuit (not properly seated)

Worst of all(!):

  • CN5 was the wrong kind of connector for this PCB. It was a micro USB receptacle, sure,  but one designed for a PCB such that in this case the logo on the cable plug faces down.
  • The result is that all the terminations are made in reversed order(!!!)
  • It took me by surprise after many confused hours. For example why was the Vbus sitting at -0.7V rather than +5V? (Because with power attached backwards the 5V rail was being clamped by the diode action of a nearby logic chip, which was getting warm, btw)

Happily, and perhaps miraculously the board is now working (at least the functions that I will be using). I removed the CN5 connector with a hot air gun (after carefully wrapping the PCB in foil to protect the rest of the board from the heat). I soldered 4 wires onto the PCB for the USB connector mounted on the baseboard.  

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2

Don’t you mean counterfeit Discovery boards? It would be good to link the seller in this thread so maybe people don’t make the same mistake. How much money did you try to save?

3

I don’t think its counterfeit when all the design files including Gerber plots are published. I’m not interested in philosophical discussions.

I do think newbs (and everyone, really) should not be burned by something like this. (The other stuff I bought at the same time was excellent value, though). 

I have no desire to communicate with these people (maybe I’ll change my mind…). I would suggest for the sake of not much $$$ when it comes to the Core (so much can go wrong in the best of circumstances in setting up etc,etc) at least get the Core from a reputable source! 

4

Ok, i guess you are right. I checked out the gerber files and ST did even include the silkscreen with their brand name (the last part seems kind of silly to me). Anyway i totally agree with you get it at a reputable source like: Mouser, Farnell, Future, Watterot and such.