Case STM32 ST-LINK Utility cannot connect Target

[Justing]

We purchased 403pcs MCUs (STM32F401VBH3) with date code 314 from Mouser website, as shown in the picture below, they have been assembled on the board,

When preparing to program them with ST-LINK utility and the programmer (ST-LINK/V2), I found that most of the MCUs could not be connected, and the utility interface said "Cannot connect Target", as shown below.

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I have analyzed it and can rule out the following influencing factors

① Poor contact between the spring probes on the test jig and the test points on the board. (Note: Verified that the contacts are good )

② Poor contact between the programmer (ST-LINK/V2) and the connector (J3) on the PCBA. (Note: Verified that the contacts are good )

③ The operating voltage of MCU (STM32F401VBH3) is abnormal.  (Note : Verified that the operating voltage is normal ,3.3V)

④ The peripheral components of MCU are abnormal.      (Note : Verified that the peripheral components are normal )

I also tried to use “Connect under reset ” and select “ lower SWD frequency mode ” , as shown below, but the connect still failed and still showed “Cannot connect to target ”

.

However, we also have 98pcs MCUs (STM32F401VBH3) with date code 746, as shown in the picture below, they are also assembled on the same board, they can be successfully connected and can be successfully programmed.

​Could you please tell me what is causing this problem and how I can fix it .

Thanks.

[SofLit]

Hello @Justing and welcome to the community,

Is it a board you have designed? you need first to check your HW/Schematics:

Especially the VCAP capacitors:

Check the V12 voltage level:

You should have V12 voltage in the range indicated in the table from the datasheet. And check if it's stable voltage and not presenting any glitch during the power-up and reset.

Check also the decoupling capacitors.

Please refer to the AN4488 "Getting started with STM32F4xxxx MCU hardware development"

PS: STLINK utility is an old tool. I recommend you to use STM32CubeProgrammer tool instead.

[Tesla DeLorean]

To add to the comments from @SofLit 

Please confirm you are using an Authentic ST-LINK/V2 and the VTarget voltage is present and measured on Pin 1 of the 20-Pin header.

Use STM32 Cube Programmer, the older tool should be fine on the F4's but the Firmware on the ST-LINK may have advanced/changed.

Observe voltage reported in tool.

Check you can observe around 1.25V on the plus side of the VCAP capacitors, and that you have around 4.7uF total capacitance.

Check you have VDDA supplied, and NRST is not clamped to ground by the IC

If you, or your PCBA, have X-Ray inspection equipment, please check the BGA, check especially pins with via-in-pad, as lack of planarization can result in uneven / non-uniform balling under the device.

Check power related pins as/where available.

>>Could you please tell me what is causing this problem and how I can fix it .

The IC presents as Non-Functional, not running internally, connecting to dead and unresponsive pins.

The capacitance at VCAP tends to present more as unexplained/erratic behaviour at a functional level, rather than just not viable for SWD/JTAG. But obvious the core needs some power, but the threshold for viability is below 1.2V

[Justing]

Thank you very much for your detailed tips, i have checked what your said and everything is normal.

[SofLit]

Hello,

Your request has been escalated internally for further analysis.

[Justing]

1. I have actually checked what you said and they are all normal and there is no problem.

2. After eliminating all the factors you mentioned, I did the experiment below.

I took a board that can be successfully programmed and a board that cannot be connected to ST-LINK Utility, and swapped the MCUs on them. After testing, the board that could be successfully programmed can no longer be connected to ST-LINK Utility, while the board that could not be connected can now be connected to ST-LINK Utility and can be successfully programmed.

3. From the above I highly doubt that there is a quality problem with MCUs like these that cannot be connected.

4. In the tool, I observed the reports for the "good" MCU and "faulty" MCU during the connection process respectively, and the results are shown in the figure below.

The ID code of the faulty MCU cannot be read, which should be the root cause of the problem.

Please help analyze the faulty MCU from this aspect. 

thanks.

[Justing]

Is there any update?

[SofLit]

Again check your HW and use STM32CubeProgrammer tool instead of STLINK-Utility as it was deprecated.

Otherwise, you can contact your local FAE for further analysis or simply submit your request on the ST online support: https://ols.st.com/

Thank you.

[SofLit]

I realized that your request was already escalated:

So please follow your request on OLS. case: 00219630