STM32H743 spi clock is distorted above 20 Mbps or higher.

[kgang]

Hi all,

I interfaced STM32H743 with external ADC(SLAVE) In master receive only mode. STM spi clk is distored seen on CRO above 20Mbps . But clk is fine till 20 mbps.so due to this received ADC values is not correct.but works fine below 20Mbps.

So how to make STM spi work at higher speed.actually STM32H7 spi supports till 150Mbps.

I configured gpio of spi to very high speed.

Any help is highly appreciated.

Regards,

Krishna.​

[Uwe Bonnes]

External means off-board? Then care for the connections! If onboard, what is the GPIO Speed of the related SPI gpios? How are the connections routed? Asd you measure, perhaps you disturb with the scope probes. Perhaps you latch on the wrong edge. A lot of things for you to check!

[TDK]

Works fine for me at 40 MHz. Nearly perfect square wave. Perhaps you can show a picture of what you mean by "distorted".

[waclawek.jan]

> I configured gpio of spi to very high speed.

Try some of the lower settings, even if this sounds counter-intuitive.

Review return/grounding arrangement, consider termination. Connections longer than 10cm should be made carefully, flying leads and breadboards are simply no.

Keep in mind that digital signals of tens of MHz with fast edges are in fact analog signals with frequencies going well beyond 1GHz.

JW