Setting up HSE on NUCLEO-H743ZI2 Development Board

[HMsDobby2]

Hello, 

I want to use the HSE of the NUCLEO-H743ZI2 development board. I tried to set it up according to the instructions in the user manual using MCO from STLINK-V3E.

Here's my setup:

However, when I checked STLinkUpgrade, I found that the HSE is set to 8.33MHz.

In the clock configuration, should I set the input frequency of HSE to 8Hz or 8.33MHz?

Thank you very much for your guidance.

[Pavel A.]

> should I set the input frequency of HSE to 8Hz or 8.33MHz?

A very good question))

Many examples assume 8 MHz clock so you can be tempted to use this. But note that the 8 MHz comes from internal oscillator (HSI), which is imprecise. And if you want a precise crystal (HSE) - you get 8.3(3) Mhz, which comes from 25 Mhz divided by 3.

[SofLit · Accepted solution]

Hello,

Let me first thank you for this question.

Indeed, you need to set HSE source of your MCU to 8.33MHz as it is a source coming from HSE of the ST-LinkV3 module divided by 3: 25MHz/3 = 8.33MHz.

This is an oscilloscope screenshot probing ST-LINKV3 MCO output and showing the 8.33MHz:

In STLINK V2 = MCO output frequency is 8MHz.

[Tesla DeLorean]

I'd set HSE_VALUE to 8333333 so speeds and baud rates are correct.

You could use the 8 MHz HSI sourced clock from the ST-LINK, but that would not be good for CAN /USB peripheral

[SofLit]

An update + good news:

The latest ST-LINKV3 firmware version V3J14M5B5 supports a MCO output frequency of 5MHz (25MHz/5) which is an integer value (HSE as source). 

So please use ST-LinkUpgrade.exe tool (downloadable from here) and select 5MHz as shown below:

[Tesla DeLorean]

That is excellent news, thanks for the update