UART STM32L0, Parity bit implementation

[ibrahim]

Posted on June 24, 2016 at 09:22

Hello,

I am setting up communication via USART2 Asynchronous to receive my data. Configuration for receive the data is 9600/7bit/1-bit stop/Parity Even/Mode Rx/Tx. The implementation works fine when no parity is implemented. But the specification dictates that even parity should be supported. If added the parity, I received any value.I do not understand where is the problem. My configuration is with STMCubeMx for STM32L031K6 nucleo.

void
MX_USART2_UART_Init(
void
)
{
huart2.Instance = USART2;
huart2.Init.BaudRate = 9600;
huart2.Init.WordLength = UART_WORDLENGTH_7B;
huart2.Init.StopBits = UART_STOPBITS_1;
huart2.Init.Parity = UART_PARITY_NONE;
huart2.Init.Mode = UART_MODE_RX;
huart2.Init.HwFlowCtl = UART_HWCONTROL_NONE;
huart2.Init.OverSampling = UART_OVERSAMPLING_16;
huart2.Init.OneBitSampling = UART_ONE_BIT_SAMPLE_DISABLE;
huart2.AdvancedInit.AdvFeatureInit = UART_ADVFEATURE_RXOVERRUNDISABLE_INIT|UART_ADVFEATURE_DMADISABLEONERROR_INIT;
huart2.AdvancedInit.OverrunDisable = UART_ADVFEATURE_OVERRUN_DISABLE;
huart2.AdvancedInit.DMADisableonRxError = UART_ADVFEATURE_DMA_DISABLEONRXERROR;
if
(HAL_UART_Init(&huart2) != HAL_OK)
{
Error_Handler();
}
}
void
HAL_UART_MspInit(UART_HandleTypeDef* uartHandle)
{
GPIO_InitTypeDef GPIO_InitStruct;
if
(uartHandle->Instance==USART2)
{
/* Peripheral clock enable */
__HAL_RCC_USART2_CLK_ENABLE();
/**USART2 GPIO Configuration 
PA9 ------> USART2_TX
PA10 ------> USART2_RX 
*/
GPIO_InitStruct.Pin = GPIO_PIN_9|GPIO_PIN_10;
GPIO_InitStruct.Mode = GPIO_MODE_AF_PP;
GPIO_InitStruct.Pull = GPIO_PULLUP;
GPIO_InitStruct.Speed = GPIO_SPEED_FREQ_VERY_HIGH;
GPIO_InitStruct.Alternate = GPIO_AF4_USART2;
HAL_GPIO_Init(GPIOA, &GPIO_InitStruct);
/* Peripheral interrupt init */
HAL_NVIC_SetPriority(USART2_IRQn, 0, 0);
HAL_NVIC_EnableIRQ(USART2_IRQn);
}
}
void
HAL_UART_MspDeInit(UART_HandleTypeDef* uartHandle)
{
if
(uartHandle->Instance==USART2)
{
/* Peripheral clock disable */
__HAL_RCC_USART2_CLK_DISABLE();
/**USART2 GPIO Configuration 
PA9 ------> USART2_TX
PA10 ------> USART2_RX 
*/
HAL_GPIO_DeInit(GPIOA, GPIO_PIN_9|GPIO_PIN_10);
/* Peripheral interrupt Deinit*/
HAL_NVIC_DisableIRQ(USART2_IRQn);
}
} 
void
MX_GPIO_Init(
void
)
{
GPIO_InitTypeDef GPIO_InitStruct;
/* GPIO Ports Clock Enable */
__HAL_RCC_GPIOA_CLK_ENABLE();
__HAL_RCC_GPIOB_CLK_ENABLE();
/*Configure GPIO pin Output Level */
HAL_GPIO_WritePin(GPIOB, GPIO_PIN_3, GPIO_PIN_RESET);
/*Configure GPIO pin : PB3 */
GPIO_InitStruct.Pin = GPIO_PIN_3;
GPIO_InitStruct.Mode = GPIO_MODE_OUTPUT_PP;
GPIO_InitStruct.Pull = GPIO_NOPULL;
GPIO_InitStruct.Speed = GPIO_SPEED_FREQ_LOW;
HAL_GPIO_Init(GPIOB, &GPIO_InitStruct);
}
/*********************** interruption **********************/
void
HAL_UART_RxCpltCallback(UART_HandleTypeDef *huart)
{
if
(huart->Instance == USART2) 
//current UART
{ 
Receive();
HAL_UART_Receive_IT(&huart2, Rx_data, 1); 
}
}
/******************** Main ******************************/
int
main(
void
)
{
HW_Init();
HAL_UART_Receive_IT(&huart2, Rx_data, 1); 
while
(1)
{
}
}

#cubemx #hal #stm32 #stm32l0 #uart

[Tesla DeLorean]

Posted on June 24, 2016 at 09:46

Observe that it say ''7 bits including parity'', for 7E1 you need to specify 8-bits with parity. And you will want to mask the data read from the Receive Data Register.

At the moment you are configuring 6E1

[ibrahim]

Posted on June 24, 2016 at 10:55

Thank you for your reply,

I did not understand, the data is 7-bit with party so I have to 8 bits (Including party) why? and why do my mask register is on how much? and after i add huart2.Init.Parity = UART_PARITY_EVEN; or No . thnks

[Tesla DeLorean]

Posted on June 24, 2016 at 16:57

Because that's how the hardware was designed and works.

7 + 1 = 8 data = USARTx->RDR & 0x7F; // To ensure the high order bit is not reflected in the data read For 7E1

huart2.Instance = USART2;
huart2.Init.BaudRate = 9600;
huart2.Init.WordLength = UART_WORDLENGTH_8B;
huart2.Init.StopBits = UART_STOPBITS_1;
huart2.Init.Parity = UART_PARITY_EVEN;

[ibrahim]

Posted on June 28, 2016 at 11:49Thank you very much for your answer :)