STM32F405 Can not connect to target

[Mhushki]

Hello All, I Hope you are well.

I am facing a problem that I spent A LOT of time on. I designed a custom board featuring the STM32F405RGT6 but i cannot connect to it at all.. I will attach the schematic and the board's pictures below. (The schematic is a PDF where I attached the sheet of the MCU's circuitry only there are other sheets for other parts of the board)

Things to mention:
1- I've assembled the board myself (But i checked the connectivity and voltages on the necessary nodes by a multimeter and i tested on the chip's pins not on the PCB pads and got the following:

-VDD on all VDD pins are 3.31V (measured directly on the pins)

-VDDA is also supplied by the same source with around 3.31V (measured directly on the pins)

-Vcap1 and Vcap2 are both 1.26V (measured on the the two Caps of 2u2 value)

-Reset Pin is 3.31V

)

2- I got suspicious about the SWD pinout that i did so i used an adapter and a Nucleo board's ST-Link to connect to my board where I measured the resistance between the SWD Pins and the Nucleo board and all are connected with reasonable resistance (Under 10 Ohms) (I got so desperate of the cause that I replaced the termination resistors of 49R9 with 0Ohms ones)

3- I got in both modes of Boot0 being Low and High. (Boot1 is floating would that cause the lack of connectivity?)

Am I missing something?!

Any kind of help would be much much appreciate. Thank you in Advance.

 

 

[Mhushki]

Hello again, 

Vdd on the ST-link is 3.38V and this is what i got in the CubeProgrammer:

Should i just give up and replace the chip when i get some stock? it doesn't seem dead to me but it's driving me crazy why can't I connect to it!!

[AScha.3]

Hi,

it tells : 

So what you use here ? a st-link ? or a nucleo-F446 board ??

[Mhushki]

I'm using the st-link part of the nucleo board (stm32F446RE) (and it'sworth mentioning that the actual chip F446 is not on the board anymore after it got burned few weeks ago) ,, I read in ST's application note (UM1724) that there are two jumpers i can take them off and use the St-link to program external chips by the SWD header 

 And as i mentioned in one of the previous replies, that using the same method successfully identified the stm32f103 on a bluepill board with no issues.

[AScha.3]

Yes, i read it, and using it as st-link is ok - and should work.

Just try : in CubeProgrammer

- mode : normal (or hot plug)

- reset mode : software

[Mhushki]

Same issue for both cases of Normal & Hot Plug

[Mhushki]

Is it safe to say that the chip is dead? Would excessive heat from soldering/reflow cause such behaviour?! 

What's puzzeling me is that the internal regulator voltages on the Vcaps are perfect and the reset voltage is pulled high and all is ok.. and when i toggle between boot0 being low and high i realize that the current consumption is slightly higher in the case of boot0 being pulled high .. which indicates that the chip is alive! Or not necessarily?! 

I genuinely wish that things would just simply work because I've almost read all related threads and complains and there's always something that can be measured on some pin to indicate that something is not right.. but in my case I don't know what it is...

[AScha.3]

Thats bad.

I never had such problem , if swd /swc / gnd + vdd (at 3v3) , it always connects. (software mode reset)

So if you sure, you connect this view lines 100% correct ....did you anything, that the target cpu could be damaged ?

If "maybe" - replace it.

[Mhushki]

>>I never had such problem , if swd /swc / gnd + vdd (at 3v3) , it always connects. (software mode reset)

-I just tested the voltages of such connections on the st link's swd header and got the following:

VDD is 3.3V

SWCLK is 0V

SWDIO is 3.3V

Should the SWCLK be high as well? Is this the faulty thing in here?

[AScha.3]

Look with a scope .... DMM is useless. On connect , you should see the st-link sending .

+

check - without power - for any short to gnd or vdd or neighbor pin.

[MM..1]

Hi Mhushki , your protection elements is ?? Go down with speed under 1MHz or remove this "protection" and too check 49R9 or replace to 0R on SWCLK and SWDIO. For simple programing is only this two required plus GND.