STM32F746ZGT6 problem with custom board [urgent]

[aksulumdeniz]

Posted on July 04, 2017 at 21:00

Dear all,

   We have been developing a custom board featuring STM32F746ZGT6, and we have encountered some problems.

   We are able to program the MCU using the ST-link with no problems, however, the MCU does not do anything! The PCB design was exactly based on the NUCLEO-STM32F746ZG board. We could not spot any differences between the NUCLEO board and our custom designed board (for the essential MCU components).  

   At first, we thought that it was a software problem so we tried the same software with the NUCLEO board and it worked fine. All the clock sources etc. are identical in both the NUCLEO and our custom board. Therefore we suspect that there is a problem with the hardware. It could perhaps be due to EMI?

   We have double checked all the connections and soldering.

   We are in a desperate situation. Do you have any ideas what could be the source of such a problem? 

All help would be appreciated. Please let me know if you need any more information.

All the best,

Mehmet Deniz Aksulu

#stm32f7 #no-response-from-the-target #custom-board

[Andrei Chichak]

Posted on July 04, 2017 at 21:25

Is your crystal ringing?

[aksulumdeniz]

Posted on July 04, 2017 at 21:28

No. There is only a slight voltage offset. I can send you the oscilloscope images tomorrow.

We soldered the same crystal and capacitors to the NUCLEO board and uploaded the same software. The oscillator is ringing there... 

[Andrei Chichak]

Posted on July 04, 2017 at 21:35

Don't bother. What you want to do is start a project in CubeMX that does very little. Set up the clock chain the way you would expect, but turn on MCO1 and MCO2 to show you what the various clocks are doing.

Try using the internal high speed clock and make sure you can see something correctly on pins 99 and 100. If that works, flip over to your external crystal.

Unless you can get your clock stable, you're going nowhere.

Andrei

[Nicholas Yunker]

Posted on July 06, 2017 at 14:16

Does the crystal you are using have the same Load Capacitance as the crystal used on the Nucleo board?  If not, you will have to change the value of the load capacitors you are hanging off the crystal inputs.  There are app notes written by ST on how to calculate these values based on the crystal you choose.

[aksulumdeniz]

Posted on July 06, 2017 at 14:55

We are using the load capacitance values given in the datasheet of the crystal we are using. We have successfully soldered the same crystal (with the same load capacitances) to the NUCLEO board, and it worked OK.

Also, even when we only activate the internal oscillator, the MCU does not work. I doubt that it has anything to do with the crystal.

Thanks

[waclawek.jan]

Posted on July 06, 2017 at 15:13

aksulu.mehmet_deniz wrote:

Also, even when we only activate the internal oscillator, the MCU does not work.

How do you know that 'MCU does not work'?

What do you expect it to do and what does it do?

Did you burn some code into it? How?

Did you measure voltage levels on pins Clive mentioned above?:

BOOTx pins?

Voltages at VCAP pins?

State of NRST?

Are all VCC and GND pins connected properly (including the analog VCC/GND)?

JW

[aksulumdeniz]

Posted on July 07, 2017 at 10:58

Dear all,

I have managed to debug the code. The code gets stuck at this place:

I did not enable the WWDG.

Do you know how to solve this?

All the best,

Mehmet Deniz Aksulu

[Tesla DeLorean]

Posted on July 07, 2017 at 11:22

Probably also the address for the Default_Handler, check .MAP file.

What's the last thing you step through before you reach this point? Double check the IRQHandlers are linking properly, ie no C++ name mangling, and that you have handlers for everything being enabled.