Author Topic: Did I actually find a defective STM32?  (Read 857 times)

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Offline mck1117

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Did I actually find a defective STM32?
« on: April 15, 2021, 12:53:20 am »
STM32F427VGT6.  Should be 1MB flash, right?

Then what's up with this?

  • Mass erase: works, erases sectors 0-11
  • Write: works, can write to full 1MB
  • Single sector erase: doesn't work, either stlink or from firmware running on the device (see attached).

What's going on with this MCU? Other identical MCUs on identical boards work just fine.  Is this a b-grade QC-fail chip that JLCPCB sold me anyway?
 

Offline wraper

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Re: Did I actually find a defective STM32?
« Reply #1 on: April 15, 2021, 01:02:19 am »
Are other identical MCUs from the same batch? Are markings and package exactly the same?
 

Offline AndyC_772

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Re: Did I actually find a defective STM32?
« Reply #2 on: April 15, 2021, 09:59:34 am »
Check option bytes. Is that sector write protected?

Offline mck1117

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Re: Did I actually find a defective STM32?
« Reply #3 on: April 15, 2021, 06:23:46 pm »
Nope, I even tried write protecting then un-protecting every sector in case it was a dodgy option byte.  And it's not just sector 11 - it's the last 4 sectors, top 512K, the ones that would be absent on a 512k part.
 

Offline mck1117

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Re: Did I actually find a defective STM32?
« Reply #4 on: April 15, 2021, 06:38:29 pm »
Are other identical MCUs from the same batch? Are markings and package exactly the same?

Yep, the markings perfectly match other 427VGT from the same and other batches. 
 

Offline DavidAlfa

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Re: Did I actually find a defective STM32?
« Reply #5 on: April 15, 2021, 06:50:32 pm »
I woudl ask such technical question in ST's site: http://community.st.com

Probably someone had the same issue.
« Last Edit: April 15, 2021, 06:52:08 pm by DavidAlfa »
Stm32 soldering station firmware: https://github.com/deividAlfa/stm32_soldering_iron_controller
Want support for your board? Put detailed info in the forum and get ready for testing. Issues? Before reporting, always flash the latest github FW and make a full reset.
Please use the forum, don't PM me!
 

Offline wraper

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Re: Did I actually find a defective STM32?
« Reply #6 on: April 15, 2021, 07:06:06 pm »
Could be some obscure issue not caught by automated testing during production.
 

Offline AndyC_772

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Re: Did I actually find a defective STM32?
« Reply #7 on: April 15, 2021, 07:06:56 pm »
it's the last 4 sectors, top 512K, the ones that would be absent on a 512k part.

You might be surprised just how absent they aren't...!

I've certainly found perfectly good flash memory where it shouldn't exist on smaller STM32 parts - just don't rely on it being there or working.

If I were you I'd just swap the chip and forget about it. If the fault happens again, then investigate.

Offline mck1117

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Re: Did I actually find a defective STM32?
« Reply #8 on: April 15, 2021, 08:39:42 pm »
You might be surprised just how absent they aren't...!

I've certainly found perfectly good flash memory where it shouldn't exist on smaller STM32 parts - just don't rely on it being there or working.

Yes - I'm aware that sometimes the higher flash parts are down-binned as smaller ones, but the surprising part here is that the flash sort of works, but the "how big am I" register still reports 1MB.

If I were you I'd just swap the chip and forget about it. If the fault happens again, then investigate.

Yep, chip already replaced, and this is the only one I've ever seen like this.
 

Offline barycentric

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Re: Did I actually find a defective STM32?
« Reply #9 on: April 24, 2021, 06:42:30 am »
Production is limited. People are probably reducing QA and stuffing good lines with (marginal) reject parts.
 
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Offline technix

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Re: Did I actually find a defective STM32?
« Reply #10 on: April 27, 2021, 02:31:18 am »
OTOH I think this is still a perfectly good STM32F427VET6 then?
 


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