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Backstory:
I have STM32F411E-DISCO board which has on-board st-link which i used before without problems (also programming external stm's). Today i tried to program STM32F103C8T6 with SWD connector (CN2) on Discovery board without success.

Problem:
After that i put jumpers (CN3) back to connect with STM32F411 and it refused to connect with error "STLink USB communication error" in ST-LINK Utility which never happend before (for F4). pic

What i checked:
I've already checked diodes D3 and D1 voltages and seems correct, LEDs LD2 and LD1 are bright red. Programing ic seems not damaged because despite of getting little warm after while (but not really hot), ST-Link Utility returns its serial number and firmware version but fails to detect stm32 target.
pic

Im bit confused because it looks like programmer is fine but still fails to connect any stm32. What should i check to identify source of error and possibly to fix it?

Edit 1: After some digging i found trace.log, it confirms detection of st-link and after second try to connect gives some usb error.

pic

Edit 2: After more extensive search i found out that when st-link tries to connect, SWDIO actually works but nothing is sent because SWCLK is always pulled low, and do not send any clock "pulses". Im guessing that my ST-Link SWCLK pin is burned and is hard pulled low.
Also checked target and it seems ok, another ST-Link connects to it just fine. Last question, is it possible that anything else could be burned instead of pin?
Because im looking in schematics (page 29) and i do not see anything bringing me hope.

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  • \$\begingroup\$ Is there another jumper/switch/connection that could have changed, maybe while you moved the board, or a cat played with it. \$\endgroup\$
    – domen
    Commented May 24, 2019 at 7:39
  • \$\begingroup\$ @domen All necessary jumpers/switches are in place and still it doesnt work. \$\endgroup\$
    – Hubert Dylewski
    Commented May 24, 2019 at 9:13
  • \$\begingroup\$ Well, what can be said. This worked, and it doesn't work anymore - something changed, either hardware (cables, jumpers, short caused by particle, some hardware component broke, ...) or software (configuration issue, update to non-working for your setup, driver issues). Have you got any replacements (st-link, target, even PC) that you could try? \$\endgroup\$
    – domen
    Commented May 24, 2019 at 10:13
  • \$\begingroup\$ @domen i can borrow simillar board from friend and try connecting it to my target and my st-link to his target but im worried about damaging his board. I guess i have to take a risk \$\endgroup\$
    – Hubert Dylewski
    Commented May 24, 2019 at 14:52

2 Answers 2

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Programing ic seems not damaged because despite of getting little warm after while

On the contrary, that is clear evidence of damage. Or at least misconnection. If this behavior persists with the target unconnected, then it is damaged.

In normal operation it will not be a noticeable source of heat.

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In normal operation it will not be a noticeable source of heat.

Im guessing that my ST-Link SWCLK pin is burned and is hard pulled low.

I replaced faulty STM32F103 which served as st-link and programmed it with UART and bootloader.
Works like a charm, so if anyone has same problem, best way is to replace it.

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