Cannot connect to the target through SWD.

kelvin · ‎2015-05-13

Posted on May 14, 2015 at 08:50

I could not connect the target (STM32F103ZET6) through ST-LINK or j-link(Both emulators are work well on other demo boards).

The MCU is powered by at 2.7V. Strangely , I've checked all the connections of the SWD interface and they seems ok. A 10kR pull-down was connected to SWCLK and a 10kR pull-up was connected to SWDIO

I put the probes on the SWDIO and SWCLK signal(CH1:SDIO,CH2:SWCLK,CH3:VDD) and the SWDIO waveform look very strange. It seems it can not be pull down to zero in some period but not all the time.Removing the pull-up resistor on SWDIO also doesn't help!

Is anyone see this before? The MCU is a brand new one and I believe should be no program on it.

#swd

Tesla DeLorean · ‎2015-05-14

Posted on May 14, 2015 at 17:20

Usually when the chips non-functional, wired incorrectly, or the orientation is wrong.

Make sure you have the states of BOOT0/1 controlled at reset. With BOOT0 High you should enter the System Loader, not whatever is in FLASH. Does that work?

Check the state of NRESET. Have an external 10K pull-up, make sure it's not stuck low, or driven High/Low with Push-Pull drivers by anything else on your board.

Check the connectivity of the Analogue Supply pins.

Using USART1 PA9/PA10 send the 0x7F character to the System Loader at 9600 8E1, do you see an 0x79 response?

Check other threads covering topic area.

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kelvin · ‎2015-05-22

Posted on May 22, 2015 at 11:40

It's a low level error. Just realized that the VADDA was unconnected.The problem has ben fixed now.