multiprocessor mode using USART in STM32F303VC at 312500 baud rate

[Rkuma.1964]

hi stm,

i am using multiprocessor communication uart mode in STM32F303VC. i am not able to communicate UART2 at 312500 baud rate. i am using external oscillator of 10 MHz . please suggest what should be the clock setting for that.

thanks,

roushan

[waclawek.jan]

What did you do so far?

Read out and check/post the RCC and UART register content. Try transmitting from UART and observe the Tx pin using oscilloscope or logic analyzer.

JW

[Rkuma.1964]

i can able to receive correct data at 115200 baud rate.

but can able able to get at 312500.

i have checked with oscilloscope. only spikes is coming instead of logic high. please check the image.

thanks

Roushan

[Piranha]

Could it be connector or ground issues between devices?

[Rkuma.1964]

hi,

But it is working perfectly at lower baud rate i.e 115200. is there anything related to UART peripheral clock?

i am using 10MHz.

thanks

Roushan

[waclawek.jan]

> But it is working perfectly at lower baud rate i.e 115200

Show.

And post the registers content, too.

JW

[waclawek.jan]

And the first frame on that picture looks quite OK, what's that?

Also, what exactly is your hardware?

JW

[Rkuma.1964]

And the first frame on that picture looks quite OK, what's that?

-> first frame is transmitted data and second is received data whatever we have send.

what exactly is your hardware?

-> i am using rs485 for the communication.

But it is working perfectly at lower baud rate i.e 115200

-> image attached.

baud rate 115200 setting;

 huart2.Instance = USART2;

 huart2.Init.BaudRate = 115200;

 huart2.Init.WordLength = UART_WORDLENGTH_9B;

 huart2.Init.StopBits = UART_STOPBITS_1;

 huart2.Init.Parity = UART_PARITY_NONE;

 huart2.Init.Mode = UART_MODE_TX_RX;

 huart2.Init.HwFlowCtl = UART_HWCONTROL_NONE;

 huart2.Init.OverSampling = UART_OVERSAMPLING_8;

 huart2.Init.OneBitSampling = UART_ONE_BIT_SAMPLE_DISABLE;

 huart2.AdvancedInit.AdvFeatureInit = UART_ADVFEATURE_NO_INIT;

 if (HAL_MultiProcessor_Init(&huart2, 10, UART_WAKEUPMETHOD_ADDRESSMARK) != HAL_OK)

 {

  Error_Handler();

 }

 if (HAL_MultiProcessorEx_AddressLength_Set(&huart2, UART_ADDRESS_DETECT_7B) != HAL_OK)

 {

  Error_Handler();

 }

uart peripheral clock is 10MHz.

thanks

roushan

[Piranha]

IMHO the spikes are unacceptably high/low. That is because of unmatched impedance. The faster you go, the more impedance matters.

https://en.wikipedia.org/wiki/Characteristic_impedance

[Piranha]

The signal for first frame doesn't seem to be properly terminated.