Hello!
In my project, the task is Automatic baud rate detection in LIN UART mode. To test this possibility, I use the NUCLEO G070 board and Lin transceiver TJA1020
I wrote a small code that allows you to receive and transmit data in UART
With a conventional UART, everything turned out to be simple, the data transfer rate is determined automatically. Since I plan to use the LIN UART, the baud rate detection mode 0x55 character frame was selected
static void MX_USART2_UART_Init(void)
{
huart2.Instance = USART2;
huart2.Init.BaudRate = 115200;
huart2.Init.WordLength = UART_WORDLENGTH_8B;
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_16;
huart2.Init.OneBitSampling = UART_ONE_BIT_SAMPLE_DISABLE;
huart2.Init.ClockPrescaler = UART_PRESCALER_DIV1;
huart2.AdvancedInit.AdvFeatureInit = UART_ADVFEATURE_AUTOBAUDRATE_INIT;
huart2.AdvancedInit.AutoBaudRateEnable = UART_ADVFEATURE_AUTOBAUDRATE_ENABLE;
huart2.AdvancedInit.AutoBaudRateMode = UART_ADVFEATURE_AUTOBAUDRATE_ON0X55FRAME;
if (HAL_UART_Init(&huart2) != HAL_OK)
{
Error_Handler();
}
if (HAL_UARTEx_SetTxFifoThreshold(&huart2, UART_TXFIFO_THRESHOLD_1_8) != HAL_OK)
{
Error_Handler();
}
if (HAL_UARTEx_SetRxFifoThreshold(&huart2, UART_RXFIFO_THRESHOLD_1_8) != HAL_OK)
{
Error_Handler();
}
if (HAL_UARTEx_DisableFifoMode(&huart2) != HAL_OK)
{
Error_Handler();
}
}void USART2_IRQHandler(void)
{
HAL_UART_IRQHandler(&huart2);
HAL_UARTEx_ReceiveToIdle_IT(&huart2, send_buff1, 16);
}void HAL_UARTEx_RxEventCallback(UART_HandleTypeDef *huart, uint16_t Size){
if (huart == &huart2){
if(send_buff1[0]!=0x55){
SET_BIT(huart2.Instance->RQR, USART_RQR_ABRRQ);
}
HAL_UART_Transmit_IT(&huart2, send_buff1, Size);
}
}From the terminal to the microcontroller in UART, I send the character set U123456789, and the microcontroller sends the same character set back to the terminal, and this happens at different baud rates. Everything works great!!!
static void MX_USART2_UART_Init(void)
{
...........................
huart2.Init.BaudRate = 19200;
...............................
huart2.AdvancedInit.AutoBaudRateMode = UART_ADVFEATURE_AUTOBAUDRATE_ON0X55FRAME;
....................................................
if (HAL_LIN_Init(&huart2, UART_LINBREAKDETECTLENGTH_11B) != HAL_OK)
{
Error_Handler();
}
}__HAL_UART_ENABLE_IT(&huart2, UART_IT_LBD);void USART2_IRQHandler(void)
{
HAL_UART_IRQHandler(&huart2);
if(__HAL_UART_GET_FLAG(&huart1,UART_FLAG_LBDF) != RESET){
SET_BIT(huart1.Instance->ICR, USART_ICR_LBDCF);
HAL_UARTEx_ReceiveToIdle_IT(&huart2, send_buff1, 16);
}
}void HAL_UARTEx_RxEventCallback(UART_HandleTypeDef *huart, uint16_t Size){
if (huart == &huart2){
if(send_buff1[1]=0x55){
HAL_UART_Transmit_IT(&huart2, SlaveData, 2);
} else
{
if(__HAL_UART_GET_FLAG(&huart2,UART_FLAG_ABRE) != RESET) {
SET_BIT(huart2.Instance->RQR, USART_RQR_ABRRQ);
}
}
}
}In this mode, the automatic baud rate is not detected.
Please tell me how to correctly determine the data transfer rate in LIN UART mode?
My assumption is that the microcontroller cannot automatically detect the baud rate due to the break field. If you work with a regular yuart, then the frame starts from 0x55 and this one worked. But when working with LIN, there is a break field before the synchronization field, due to which a frame error may occur. Возможно, по �?той причине автоматиче�?кое определение �?коро�?ти передачи не работает в режиме LIN UART.
This is how the frame looks from the master device to the LIN transceiver
