maximum USART baud rate on STM32U0

[max_hai]

Hi,

I would like to determine the maximum baud rate for a USART peripheral in asynchronous mode. In the datasheet (Figure 1) the maximum baud rate is given as 8 MBit/s. But even if I set the clock for the USART peripheral (in this case USART1) to the maximum of 56 MHz (Figure 2), I'm not able to set 8 MBit/s for the baud rate. I'm able to set 7 MBit/s when I set the over-sampling to 8 samples (image3).

I'm using the Nucleo-U083 board together with the STM32CubeIDE 1.16.1.

If someone could show me how to configure the USART peripheral for 8MBit/s I would be very happy.

Kind regards Max.

image1:

image2:

Image3:

[Guenael Cadier]

Hello @max_hai 

As per my understanding, as STM32U0 max operating frequency is 56Mhz, the maximum baudrate achievable on an USART peripheral in asynchronous mode, is 56/8, so 7Mbit/s when selecting Oversampling 8 method (3.5 in Oversampling 16). So my feeling is that the information in Datasheet is not exact.

Regards

[max_hai]

Hello,

Could you please verify this information?

Because I just noticed that I can increase the USART1 clock without getting an error for that clock. But in this case I get an error for other clock domains that can only handle 56MHz, as you can see in the screenshot below. So I'm probably doing something wrong here, and a higher USART clock can be achieved with an external oscillator? But even this I cannot configure.

Regards

[Andrew Neil]

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@Guenael Cadier wrote:

 the maximum baudrate achievable on an USART peripheral in asynchronous mode, is 56/8, so 7Mbit/s  

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So is the 8Mbps achievable in synchronous mode ?