STM32L072 power or startup issue

[ashah.16]

Hi,

I recently purchased STM32L072 MCU and designed my own PCB which has the HSE and LSE crystals. I found a weird problem when I power the MCU.

-Once I connect the power, it consumes 10 mA. I programmed the MCU, without any issue. But, I found that the code never executes. Even in debug mode, the code does not start even the first function. From what i found, the system clock source is not working and it consumes 10 mA.

-When I quickly connect and disconnect the power, at some point the clocking system starts working and then the MCU starts executing functions. When it is working, it consumes 1-2 mA which makes sense. At every power ON action I have to do the same.

-I put a probe of oscilloscope on a pin of crystal, it is a proof. There is no signal on this pin when it consumes 10mA, while I see a perfect 8 MHz signal when it is running and consumes 1-2 mA.

-I tried the internal HSI as well, and the problem is similar.

Can you help to understand why this issue exists? I tried two chips and they both have this problem.

Best,

Amir

[Tesla DeLorean · Accepted solution]

BOOT0 pulled LOW?

[ashah.16]

Right after the question I tried this and worked very well.

Thanks.

So, another question related to this BOOT0 pin. Even if I plan later to update the firmware with UART over USB, should the state of this pin change to 1 ?

Thanks

[Tesla DeLorean]

You can drive it high and reset to get into the ROM System Loader, or jumper it such that you can pull up or down