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I have made a control board with STM32F769IIT6. External 25MHz oscillation does not occur, so chip doesn't work.

HANIK.1
Associate II

PDR_ON is at high, BOOT0 is at high, NRST is at high, BYPASS_REG is at low. VDD12DSI and VCAPDSI is at low with 2.2uF and 100nF. I have put as much as possiple decoupling caps. 25MHZ crystal (Jauch) with 18pF capasitances, they are so close to chip. But crystal doesn`t oscillates, so chip is not working. What else sholud be?

5 REPLIES 5
Danish1
Lead II

How strongly do you know that a problem with the external oscillator is what is stopping your board from working?

stm32 have internal HS oscillators that they use at start-up and with the built-in bootloader.

Can you connect over JTAG / SWD? Or any of the interfaces that the bootloader uses?

How did you select your 25 MHz crystal? In particular what is the ESR and the load-capacitance? Did you check it against AN2867?

Hope this helps,

Danish

Piranha
Chief II

> BOOT0 is at high

That's why it "doesn't work".

The chip does not auto-magically start external clocks, you must do in software.

Your code will not run with BOOT0 = HIGH

You can't use oscillator starting as a "signs of life" indicator. Connect via SWD or JTAG, prove if you can connect to device, check if NRST driven LOW, check voltages on VCAP pins.

Wouldn't expect the loader to test HSE absent a USB connection.

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HANIK.1
Associate II

I have used stm32f769iit6, LQFP176 with DSI footprint. I got this footprint from one of the internet side, I think it is samacsys. There was a mistake on footprint, pin number 80 and 81 are misplaced. After correction, now it works.

HANIK.1
Associate II

I have used stm32f769iit6, LQFP176 with DSI footprint. I got this footprint from one of the internet side, I think it is samacsys. There was a mistake on footprint, pin number 80 and 81 are misplaced. After correction, now it works.