STM32F429 USART baudrate max rate

[YChen.51]

Hi all

I used STM32F429 connected with LTE module by USART3，but I can only set the baudrate 230600. If I set 460800 or 921600，MCU can't transmit or receive data from LTE.

How can I set the baudrate over 230600??

void uart_init()
{
	UART3_Handler.Instance=USART3;					 
 
	//UART3_Handler.Init.BaudRate=921600;
	//UART3_Handler.Init.BaudRate=460800;
	UART3_Handler.Init.BaudRate=230400;
	UART3_Handler.Init.WordLength=UART_WORDLENGTH_8B; 
	UART3_Handler.Init.StopBits=UART_STOPBITS_1;	 
	UART3_Handler.Init.Parity=UART_PARITY_NONE;	
	UART3_Handler.Init.HwFlowCtl=UART_HWCONTROL_NONE; 
 
	UART3_Handler.Init.Mode=UART_MODE_TX_RX;		  
	HAL_UART_Init(&UART3_Handler);					 
}

Regards,

[Tesla DeLorean]

Should be capable of several Mbaud.

You got transceivers or level shifters in the path?​

[YChen.51]

I am sure that the LTE module uart can reach 3000000

and no, I connect the STM32 board and LTE module directly.

[Tesla DeLorean]

Get a scope on the signals and check the timing.

Check HSE_VALUE is correct.

Many cellular modems use 1.8V signalling, no idea the make/model involved here, or specifics about board.

I'd back off on the slew-rate (SPEEDR) none of the previously mentioned speeds exceed 5 MHz, no need to put 100 MHz edges on things.

Check integrity, and ringing issues, use series resistors if necessary.

Check if you're getting Noise or Framing Errors, or Over/Underruns.

[Piranha]

Very probable that ST's buggy bloatware is incapable of keeping up with such speeds. Implement something sane like this:

https://github.com/MaJerle/stm32-usart-uart-dma-rx-tx