F103 USART1 RX IRQ happens premature.

[zhausq]

Posted on December 26, 2015 at 01:55

I am using the USART1 interface of an F103 and I'm havin trouble getting interrupts correctly. When receiving a byte the first interrupts get triggered while bit 6 is still underway and then a second interrupt happens for some unknown reason.

row1 is debug pin that is being toggled ever irqrow2 is rx pinrow3 is tx pin

http://imgur.com/IgfKKvJ

void USART1_Init(void){    /* USART configuration structure for USART1 */    USART_InitTypeDef usart1_init_struct;    /* Bit configuration structure for GPIOA PIN9 and PIN10 */    GPIO_InitTypeDef gpioa_init_struct;    /* Enalbe clock for USART1, AFIO and GPIOA */    RCC_APB2PeriphClockCmd(RCC_APB2Periph_USART1 | RCC_APB2Periph_AFIO |                           RCC_APB2Periph_GPIOA, ENABLE);    /* GPIOA PIN9 alternative function Tx */    gpioa_init_struct.GPIO_Pin = GPIO_Pin_9;    gpioa_init_struct.GPIO_Speed = GPIO_Speed_50MHz;    gpioa_init_struct.GPIO_Mode = GPIO_Mode_AF_PP;    GPIO_Init(GPIOA, &gpioa_init_struct);    /* GPIOA PIN9 alternative function Rx */    gpioa_init_struct.GPIO_Pin = GPIO_Pin_10;    gpioa_init_struct.GPIO_Speed = GPIO_Speed_50MHz;    gpioa_init_struct.GPIO_Mode = GPIO_Mode_IN_FLOATING;    GPIO_Init(GPIOA, &gpioa_init_struct);    /* Baud rate 9600, 8-bit data, One stop bit     * No parity, Do both Rx and Tx, No HW flow control     */    usart1_init_struct.USART_BaudRate = 9600;    usart1_init_struct.USART_WordLength = USART_WordLength_8b;    usart1_init_struct.USART_StopBits = USART_StopBits_1;    usart1_init_struct.USART_Parity = USART_Parity_No ;    usart1_init_struct.USART_Mode = USART_Mode_Rx | USART_Mode_Tx;    usart1_init_struct.USART_HardwareFlowControl = USART_HardwareFlowControl_None;    USART_Init(USART1, &usart1_init_struct);    /* Enable RXNE interrupt */    USART_ITConfig(USART1, USART_IT_RXNE, ENABLE);    NVIC_InitTypeDef NVIC_InitStructure;    NVIC_InitStructure.NVIC_IRQChannel = USART1_IRQn;    NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority = 0;    NVIC_InitStructure.NVIC_IRQChannelSubPriority = 0;    NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE;    NVIC_Init(&NVIC_InitStructure);    /* Enable USART1 global interrupt */    NVIC_EnableIRQ(USART1_IRQn);    /* Enable USART1 */    USART_Cmd(USART1, ENABLE);}void USART1_IRQHandler(void){ static int tx_index = 0; static int rx_index = 0; static char rx_byte;    if(USART_GetITStatus(USART1, USART_IT_RXNE))    {     rx_byte=USART1->DR;     if(rx_byte != 'x')     {     USART_SendData(USART1, rx_byte);     }     /*telemetry_rx_buffer[rx_index++] = USART_ReceiveData(USART1);     if (rx_index >= (sizeof(telemetry_rx_buffer) - 1))     rx_index = 0;*/     debugpin_cycle();    }}What am i doing wrong here? #stm32-f1-usart-uart-problem

[Tesla DeLorean]

Posted on December 26, 2015 at 02:14

What am i doing wrong here?

debugpin_cycle(); // infers something different than toggling, code not shown

[zhausq]

Posted on December 26, 2015 at 10:53

Here's what debugpin is about:

void debugpin_init(void){ GPIO_InitTypeDef GPIO_InitStructure; //configure pin as output GPIO_InitStructure.GPIO_Pin = GPIO_Pin_1; GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz; GPIO_InitStructure.GPIO_Mode = GPIO_Mode_Out_PP; GPIO_Init(GPIOB, &GPIO_InitStructure);}void debugpin_set(int value){ GPIO_WriteBit(GPIOB, GPIO_Pin_1, !value);}void debugpin_cycle(void){ GPIO_WriteBit(GPIOB, GPIO_Pin_1, 1); GPIO_WriteBit(GPIOB, GPIO_Pin_1, 0);}

[zhausq]

Posted on December 27, 2015 at 12:56

Fuck me, i was uploading release when working on debug. That's why nothing seemed to fix it. It now works great.