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_LardDork _
_LardDork _
Associate
December 28, 2017
Question

How do I setup external power supply to be used with STM32F407x Discovery board(s) instead of using mini USB?

  • December 28, 2017
  • 2 replies
  • 996 views

Posted on December 28, 2017 at 07:32

I generated an output waveform on a DAC pin and read it on ADC pin but the values which ADC showed weren't changing in steps(as designed). DAC signal on oscilloscope showed a lot of noise and hence the requirement for external supply.

Tried using a phone charger(plugged in mini usb), took off jumpers on CN3 and shorted VDD to NRST, the board powers but the clock is ridiculously slow. Also later an external 5V supply in to 5V out pin, didn't work.

Any clue how should I go about or any available documentation for this thing?

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2 replies

Tesla DeLorean
Tesla DeLorean
Guru
December 28, 2017
Posted on December 28, 2017 at 15:23

Tying NRST to VDD is definitely going to cause headaches. Don't do that.

You should be able to power the STM32F4-DISCO directly from the ST-LINK USB input, make sure you have current firmware as some of the original DISC1 shipments using version 25 would hold the part in reset.

Perhaps use some debug/telemetry output to understand what is happening, ie if the part is starting, but getting stuck some place else

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T J
T J
Senior III
December 28, 2017
Posted on December 28, 2017 at 21:44

The noise problem is likely to be ground noise.

The ground pin of the scope must be as short as possible and right on the processor ground pin.

Then most of your noise will go away.

Yes, the ST Analog-in doesn't exactly match the DAC outputs.

I use digital filtering in my work, but its never 100%.

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