STM32F207 Nucleo 144 UART1 Baud Rate

[sumit kale]

Posted on January 23, 2017 at 14:57

Hello,

i want a baud rate of 5 mbps on UART1/UART6 on STM32F207 Nucleo Board (As per reference Manual UART1 & UART6 can have baud rate up to 7.5 Mbps). However when i am configuring in STM Cube MX i am getting baud rate of 3.7 mbps max for both UART1 & UART6. I have checked clock configuration many times.

HCLK= 120 MHz, APB1= 30MHz, APB2=60 MHz exactly. In Addition to this i also tried to give Input frequency of 25MHz (26 MHz max).

Still i am unable to cross 3.7 Mbps (max possible value as per Cube Mx)

So can anybody suggest me possible solution??.

#stm32f207-uart

[Nesrine M_O]

Posted on January 23, 2017 at 15:02

Hi

Kale.Sumit

,

Could you precise in which CUBEMX versionyou have found the issue. So, we can verify it.

-Nesrine-

[Guenael Cadier]

Posted on January 23, 2017 at 15:46

Hi

Kale.Sumit

,

Just an idea ...

Highest baud rates values require to have Oversampling set to 8 (not 16).

Using an APB2 clock at 60 Mhz, with an USART oversampling set to 16, max baud rate that could be achieved is corresponding to 60/16 = 3.75 Mhz, so more or less what you experienced. Could you check Oversampling setting value when configuring your USART in Cube MX (8 or 16) ? If 16, could you try 8 instead?

Best regards

Guenael

[sumit kale]

Posted on January 23, 2017 at 15:06

STM32Cube MX 4.16.1

[Nesrine M_O]

Posted on January 23, 2017 at 16:08

Hi

Kale.Sumit

,

as it is already said by

Cadier.Guenael

try to set

Oversampling to 8 ,to have

Highest baud rates value.

Common programmable transmit and receive baud rate of up to 7.5 Mbit/s whenthe APB frequency is 60 MHz and oversampling is by 8

-Nesrine-

Ifmy suggestanswers your question, please mark it as correct.

[Guenael Cadier]

Posted on January 23, 2017 at 16:10

Just some pics to highlight what i meant :

Here is CubeMx configuration window when trying to apply 5Mhz baudrate using OverSampling rate set to 16 samples :

Now, selecting oversampling 8, extends possible baudrate range and allow reaching 5Mhz :

Regards

Guenael

[Nesrine M_O]

Posted on January 23, 2017 at 15:18

Hi

Kale.Sumit

,

please try to update MX to the latest version 4.19 , then late me know if the issue persist again

-Nesrine-

[sumit kale]

Posted on January 23, 2017 at 15:48

Hello,

In new Version (4.19) same issue. Baud rate is 3.75 Mbps for UART1

[Tesla DeLorean]

Posted on January 23, 2017 at 16:57

60 MHz / 16 = 3.75 MHz

OVER8 mode will get you higher

For high baud rates of specific value you'd likely want to start will a close multiple as the granularity of the clock becomes more dominant. High asynchronous rates aren't particularly robust/reliable, consider synchronous methods, and ones with integrity checking designed in.

[sumit kale]

Posted on January 23, 2017 at 16:15

Thank you so much..I got the Point..