stm32h723 can not connect to the targer by SWD

[Sacchy]

I am not new in using STM32H7 products but in my last project I can not connect the target by ST_Link.

I take care about power supply, pins to connect at GND or 3V3 and so on but the Link-Utility return this error:

<<

08:28:41 : ST-LINK SN : 440032001500004737364D4E
08:28:41 : V2J43S7
08:28:41 : Connected via SWD.
08:28:41 : SWD Frequency = 4,0 MHz.
08:28:41 : Connection mode : Normal.
08:28:42 : Can not connect to the target!
Please select "Connect Under Reset" mode from Target->Settings menu and try again.
08:28:53 : Unexpected error

>>

It seems the comunication start with the target but can not complete it.

I Try all possible combinations of the ST_Link Utility configurations not no results

Can anyone help me to solve this problem?

Is there a specific list of pin to connect at 3V3 or GND or with CAPS and so on in order to let the target comunicate properly.

Thanks for you support

[Peter BENSCH]

Welcome @Sacchy, to the community!

You have probably forgotten to connect the NRST connection or have not connected it correctly. In the ST-LINK/V2 documentation you will find instructions on which signals it must be connected to the target. The ST-LINK utility has also been on NRND for a long time and has been replaced by the recommended STM32CubeProg.

Hope that helps?

Regards
/Peter

[RomainR.]

Hello @Sacchy 

I recommend using STM32CubeProgrammer instead of STLink Utilities which is no longer supported and NRND.

You can download latest STM32CubeProgrammer software in our STM32 Developer Zone:

https://www.st.com/content/st_com/en/stm32-mcu-developer-zone/software-development-tools.html

Can you clarify your question by indicating if you are using a custom board and if you're using external debugger ?
Finally regarding the hardware configuration of the STM32H723, and for all the pins relating to the different power supply domains, I suggest you check your connections
1) With the application note AN5419.

https://www.st.com/resource/en/application_note/an5419-getting-started-with-stm32h723733-stm32h725735-and-stm32h730-value-line-hardware-development-stmicroelectronics.pdf
2) Compare it with a reference design like the Nucleo-H723ZG board 

https://www.st.com/en/evaluation-tools/nucleo-h723zg.html#cad-resources

3) If possible, you can share your schematic and ask to the community expert to review it.

I hope it will guide and help you?

Let me know.

Best regards

Romain

[Sacchy]

Thanks a lot for you reply

Here my CPU schematic.

The problem is not fixed at now.

I'll make some more test as soon as possible.

Connecting oscilloscope do NRTS, SWCLK and SWDIO, i see data and clock moving, then i see the reset goes down, the reset going up in 5 mSec and data and clock signal moving again.

I don't understand what it means. 

At reference manual, 65.4.1 Serial-wire and JTAG debug port (SWJ-DP), i see there is a special sequence but i can not recognise it in the oscilloscope.

Can you have a look at schematics for check if there is a problem in connections please?

Thanks a lot

[Peter BENSCH]

I don't see any serious problems in the schematics:

• R208 at Y2 is generally not necessary
• R154 at NRST is definitely not necessary because an internal pull-up at NRST ensures that C91 is charged
• C91 is slightly too large at 1µF, 100nF is sufficient

All points do not really interfere with the ST-LINK.

However, you are using a crystal with unsuitable parameters because the ESR of 40ohms and/or the load capacitance of 18pF are too high for its frequency of 25MHz. For 25MHz and CL=18pF the ESR should be approx. max. 15 Ohm, alternatively for ESR=40 CL may only be max. 8pF in order to obtain sufficient gain margin. You can calculate suitable combinations using the formulae given in AN2867 and obtain parameters like 25MHz, ESR<=28ohms, CL<=12pF, C0<=7pF.

Another very important point, which unfortunately is often not given sufficient attention, is the layout for the crystal. There is very good advice on this, which can also be found in AN2867, sections 7.1 and 7.2. Take a look at fig 14 and compare the layout with yours.

Regards
/Peter

[Tesla DeLorean]

Did this work at any point? Definitely need to be using STM32 Cube Programmer. The Utilities have been deprecated for several years at this point. Watch SMPS / LDO and VOS settings, these can lock out the processor.

Double check part orientation.

Check NRST normally high

[Sacchy · Accepted solution]

Fixed:

I use the new ST_LINKV3 instead the old STLINKV2.