: Error: No STM32 target found!

[samuelbs]

I designed my board using the STM32L476RGT6. However, when using the ST-Link via SWD, I get the following message:

Error: No STM32 target found! If your product embeds Debug Authentication, please perform a discovery using Debug Authentication.

I have checked all connections and voltages, and everything is correct, with the proper 3.3V values.

I am sending the schematic and a photo of the programmer.

Note: I did not solder the VCAP capacitors, and there is no voltage on these pins.

[tjaekel]

Do you use an ST-LINK debugger?

Have you wired NRST also to debugger header?
The "UR connection mode" seems to mean: debugger wants to connected Under Reset (it wants to force a reset and connect). But if you do not populate NRST to debugger - maybe the reason.

A forum link with similar symptom:
https://community.st.com/t5/stm32cubeprogrammer-mcus/stlink-v2-not-recognizing-stm32cubeprogrammer-ur-connection-mode/td-p/581187

[AScha.3]

At first solder the vcap caps. And verify the voltage there, about 1.3 V . This is the CPU core supply - so the most important voltage to check.

[samuelbs]

I measured 0V on the VCAP pins and a current consumption of 60mA (STM32L476RGT6 + LC76G), which I consider very high.

I am using the ST-Link from my Nucleo board, and when I reinsert the jumper, the STM32L4 on the Nucleo board works perfectly.

Additionally, I have already checked for possible shorts in the soldering or PCB and found none.

Could this be an issue with the MCU?

[AScha.3]

>0V on the VCAP pins

= core has no supply.

So check for any short on VCAP .

>Could this be an issue with the MCU?

If you didnt give 3v3 to vcap or something like that (static discharge) - cpu should be ok.

If you have another board, try it; to compare.

[samuelbs]

I checked my Nucleo-L476RG, and the VCAPs are jumpered to GND, as the datasheet states they are VSS. I tried doing the same, but it didn't work. I verified all 3V3 and GND connections, and they are okay.

Even so, the error message appears:
"Error: No STM32 target found! If your product embeds Debug Authentication, please perform a discovery using Debug Authentication."

[AScha.3 · Accepted solution]

>VCAPs are jumpered to GND, as the datasheet states they are VSS.

I dont understand this.

VCAP pins must have no connection to GND. Only 2u2 (or 4u7) cer. capacitors ,

going from vcap.pin---2u2cap.---GND.

And sure: no short to GND on any VCAP.pin ?

[samuelbs]

I found the error—I accidentally soldered the MCU rotated 360° (I confused the two markings on top of it). I corrected it, and now it works as expected.

Thank you very much for the help! I was able to learn a bit more with you.

[tjaekel]

360deg? then it would be the same.

There should be just one pin 1 marking, maybe two other "holes" for pressing the package.
Pin 1 should be on lower left corner and all the text is correct and readable.

This doc. might help next time:

https://www.st.com/resource/en/technical_note/tn1433-reference-device-marking-schematics-for-stm32-microcontrollers-and-microprocessors-stmicroelectronics.pdf

[AScha.3]

Good.

And reality looks like this:

So "a dot" is not the important thing to look for, but the alignment of the font (to read it) - and then to decide, what is the "lower left corner" with the pin1 mark.