STM32F103:Problem with USART when use System Tick Timer Delay in us

Posted on February 28, 2015 at 03:34

Hi all,

I am using STM32F103RCT6 and CP2102 as UART controller driver.

I have problem with USART when I use SysTick Timer to generate 1us Delay.

The problem is that when I configure SysTick at frequency 1Mhz, the program does not work.

SysTick_Config(SystemCoreClock / 1000000)   // SystemCoreClock is 72 Mhz

I use SysTick to generate 1us Delay: 

void Delay(__IO uint32_t nTime)

 

{ 

 

TimingDelay = nTime;        // Timing Delay is a volatile uint32_t variable

 

while(TimingDelay != 0);

 

}

 

void TimingDelay_Decrement(void)

 

{

 

if (TimingDelay != 0x00)

 

{ 

 

TimingDelay--;

 

}

 

}

 

SysTick handler

void SysTick_Handler(void)

{

 

TimingDelay_Decrement();

 

Tick++;     // my private variable for counting     

 

}

 

That is how I create my Delay function in microsecond.

It works well, but when I want to add USART code, the program doesn't work. 

When I call USART_Configuration(); in main, the program stucks.

void USART_Configuration(void)

 

{

 

USART_InitTypeDef USART_InitStructure;

 

 

RCC_APB2PeriphClockCmd(RCC_APB2Periph_USART1, ENABLE); 

 

 

 

/* Configure PA9 for USART Tx as alternate function push-pull */

 

GPIO_InitStructure.GPIO_Pin = GPIO_Pin_9;

 

GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF_PP;

 

GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;

 

GPIO_Init(GPIOA, &GPIO_InitStructure);

 

 

/* Configure PA10 for USART Rx as input floating */

 

GPIO_InitStructure.GPIO_Pin = GPIO_Pin_10;

 

GPIO_InitStructure.GPIO_Mode = GPIO_Mode_IN_FLOATING;

 

GPIO_Init(GPIOA, &GPIO_InitStructure);

 

 

/* USARTx configured as follow:

 

        - BaudRate = 115200 baud  

 

        - Word Length = 8 Bits

 

        - One Stop Bit

 

        - No parity

 

        - Hardware flow control disabled (RTS and CTS signals)

 

        - Receive and transmit enabled

 

  */

 

USART_InitStructure.USART_BaudRate = 115200;

 

USART_InitStructure.USART_WordLength = USART_WordLength_8b;

 

USART_InitStructure.USART_StopBits = USART_StopBits_1;

 

USART_InitStructure.USART_Parity = USART_Parity_No;

 

USART_InitStructure.USART_HardwareFlowControl = USART_HardwareFlowControl_None;

 

USART_InitStructure.USART_Mode = USART_Mode_Rx | USART_Mode_Tx;

 

 

/* USART configuration */

 

USART_Init(USART1, &USART_InitStructure);

 

 

/* Enable USART */

 

USART_Cmd(USART1, ENABLE);

 

}

 

I tried to configure SysTick at 100Khz (delay with resolution 10us), it worked.

SysTick_Config(SystemCoreClock / 100000);

But my application needs a delay at us. I don't know what is the reason and how to solve it. Can anyone give me some advice. 

Thank you for reading.

#it''s-deja-vu-all-over-again