STM32F405 Won't Oscillate ?!?

Rogers.Gary · ‎2015-06-15

Posted on June 15, 2015 at 23:33

Hello:

This problem has me totally dumbfounded. Please see the attached image and screen shot of schematic. An absolutely simple circuit, yet it does not want to oscillate. This is the second board (different PCB, different mfr) so it's not that, or parts. So what does that leave? I have made the identical circuit before, and in fact just copied the micro schematic page and used that. So this is really difficult to understand...I have:

-checked every pin's connectivity, and adjacent pins for shorts

-every Vdd has a cap

-vcap1, and vcap2 are installed, and show 1.23V when 3.3V is applied to the board.

-the oscillator circuit is identical to the Discovery board. Resistor is 220 ohms, caps are 20pF, and oscillator load is 20pF

Yet....the oscillator is silent. Unexplainable...can someone please provide a clue as to what is going on? Any tips on what I can do to determine what is going on?

BTW - have tried scope with both AC/DC coupling, probe at 10x

Thank you...

#stm32f4-oscillator

Tesla DeLorean · ‎2015-06-15

Posted on June 16, 2015 at 00:29

And you're enabling the HSE in the RCC? I ask because it doesn't start automatically. You don't have BYPASS mode enabled, right?

Replace the 220R with a 0 Ohm ?

Same parts work on the STM32F4DISCO with R68 removed, and SB13, SB14 open? The clock on the DISCO comes from the F103 MCO it doesn't have a series resistor.

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Rogers.Gary · ‎2015-06-15

Posted on June 16, 2015 at 00:54

clive1,

It never clicked that the HSE didn't start automatically, I should have known that from the fact it can also run internal.

Knowing what you said made me realize something weird was going on the the J-Link.

I started to look at that and it is acting very weird. All configuration is OK in the project options, and I can use it on another board with an LPC1768.

So I tried an ST-Link pod, and kaaaaaaZOWIE !!!! It's working!!!!

(I still feel like a fool because I didn't realize this sooner)

Thanks....(going to trade in my J-Link for a new one or figure out what's wrong with this one)