STM32F103RBT6 MCU not detected by programmer – BOOT0 pin tied to GND on custom PCB

[asking]

Hello everyone,

I have designed a custom PCB using STM32F103RBT6 and I’m facing a serious issue:
The MCU is not getting detected by the programmer.

Symptom:

When connecting via SWDIO, SWCLK, 3.3 V, and GND, both STM32CubeProgrammer and ST‑Link Utility fail to detect the target.

Power rails are verified: 3.3 V present at VDD pins, proper decoupling capacitors placed close to supply pins.

No shorts observed on the board.

Important hardware details:

Boot0 pin (on my design) is directly tied to GND by mistake – I’m wondering if this could block programming or reset behavior.

NRST pin has a 10 kΩ pull‑up to 3.3 V as recommended.

BOOT0 is pulled low (GND) on the board without Resistor, any problem?

Any advice would be greatly appreciated!
schematic snippet attached.

 

 

Thank you in advance for your help.

[Tesla DeLorean]

What voltage do you have on VDDA / AREF ?

Needs this for Power-On-Reset

Inspect voltage at NRST, is it clamped Low by the device?

[asking]

VDDA i am using TL431B using 10K on ground and 2.2K on positive side. Getting 3.041V and same is supplied to VDDA. 

NRST pin I have 10K pull up resistor tied to 3.3V.

[STOne-32]

Dear @asking ,

VDDA must be connected to VDD and also VBAT not left unconnected. Recommended to connect To VDD and 100nF capacitor  if no battery is present .

R1 to be removed on NRST pin we already have internal pull-up to VDD tied internally . Just keep the 100nF cap . Can you check theses points and let us know . If possible also a picture of the Package marking  .

Hope it helps you ,

STOne-32

[asking]

Thanks will try to connect VBAT to Vdd. And update.

But need to understand regarding VDDA, it needs to be stable reference so I used TL431B if I connect to VDD, it might fluctuations which can affect ADC reading. Pls advise.

[Tesla DeLorean]

>>NRST pin I have 10K pull up resistor tied to 3.3V

You said that before, that's not what I asked, is the part clamping it LOW, or can you see the HIGH level on INSPECTION? If it's stuck LOW the part will not function.

The error is indicative that the part currently isn't viable. Check part orientation

[asking]

It's have 3.3V when programming and all other conditions. There's no reset button provided which can ground the connection. 

[STOne-32]

Dear @asking ,

my recommendation is only for testing purposes first , as VDDA is the main power supply for our power on circuitry, Internal RC HSI and PLL and if not provided properly device will not power on . maximum deviation from all VDDx ( including A) is 300mV on STM32F1 series , reference voltage for ADC VREF+ is a separate pin for bigger packages such as LQFP100 and might be bounded internally to VDDA on smaller ones .  Also as recommended by @Tesla DeLorean  , please send us the real picture of the device soldered on PCB, we have seen some design where pin 1 marking is put in 90 degree versus what is supposed to be .

Hope it helps you .

STOne-32

[Tesla DeLorean]

It's not about a button, it's about the STM32F103 the POR inside will clamp to ground.

I'm asking you to OBSERVE the voltage seen on the PIN, the HIGH level if the PULL-UP is there, LOW if the device is clamping in RESET

[asking]

Ok noted. Will remove external pull-up and will read voltage on NRST pin. Will update soon