Posted on May 17, 2011 at 13:35Hi
I have a problem with synchronous USART(on USART3).I have configured related parts, but I have not any output clock whenever I send information via it.(Data can be seen with oscilloscope but clock is not available).
I am using Ride7(7.20.09.0162) as a compiler.
The part of the program which is related to USART configuration is as follow, and I will appreciate if anybody can help me to find my failure.
#define sysclock High
void USART_Configuration(void)
{
USART_InitTypeDef USART_InitStructure;
USART_ClockInitTypeDef USART_ClockInitStructure;
//USART3 configuration
#if(sysclock==High)//36MHz
USART_SetPrescaler(USART3, 0x04);//USART Clock set to 4.5MHz ((APB1CLK=18Mhz)/4)
#elif(sysclock==Low)//4MHz
USART_SetPrescaler(USART3, 0x01);//USART Clock set to 4MHz ((APB1CLK=4Mhz)/1)
#endif
USART_ClockInitStructure.USART_Clock = USART_Clock_Enable;
USART_ClockInitStructure.USART_CPOL = USART_CPOL_High;
USART_ClockInitStructure.USART_CPHA = USART_CPHA_2Edge;
USART_ClockInitStructure.USART_LastBit = USART_LastBit_Enable;
USART_ClockInit(USART3,&USART_ClockInitStructure);
USART_InitStructure.USART_BaudRate = Global_Def_USART3_Default_Baud;
USART_InitStructure.USART_WordLength = USART_WordLength_9b;//Word Length = 9 Bits
USART_InitStructure.USART_StopBits = USART_StopBits_1_5;//1.5 stop bit is transmitted at the end of frame
USART_InitStructure.USART_Parity = USART_Parity_Even;//Even parity,When parity is enabled, the computed parity is inserted at the MSB position of the transmitted data (9th bit when the word length is set to 9 data bits; 8th bit when the word length is set to 8 data bits).
USART_InitStructure.USART_Mode = USART_Mode_Rx | USART_Mode_Tx;//Tx and Rx enabled
USART_InitStructure.USART_HardwareFlowControl = USART_HardwareFlowControl_None;//Hardware flow control disabled (RTS and CTS signals)
USART_Init(USART3, &USART_InitStructure);
USART_Cmd(USART3, ENABLE);//Enable USART3
}
void RCC_Configuration(void)
{
RCC_DeInit();//RCC system reset(for debug purpose)
RCC_HSEConfig(RCC_HSE_ON);//Enable HSE
HSEStartUpStatus = RCC_WaitForHSEStartUp();//Wait till HSE is ready
if(HSEStartUpStatus == SUCCESS)
{
RCC_PCLK2Config(RCC_HCLK_Div1);//APB2CLK = HCLK
FLASH_PrefetchBufferCmd(FLASH_PrefetchBuffer_Enable);//Enable Prefetch Buffer
#if(sysclock==High)
RCC_HCLKConfig(RCC_SYSCLK_Div1);//AHBCLK = SYSCLK-36Mhz
RCC_PCLK1Config(RCC_HCLK_Div2);//APB1CLK = AHBCLK/2-18Mhz
FLASH_SetLatency(FLASH_Latency_2);//Flash 2 wait state
RCC_PLLConfig(RCC_PLLSource_HSE_Div2,RCC_PLLMul_9);//PLLCLK = 8MHz/2 * 9 = 36 MHz
RCC_PLLCmd(ENABLE);//Enable PLL
while(RCC_GetFlagStatus(RCC_FLAG_PLLRDY) == RESET)//Wait till PLL is ready
{
}
RCC_SYSCLKConfig(RCC_SYSCLKSource_PLLCLK);//Select PLL as system clock source
while(RCC_GetSYSCLKSource() != 0x08)// Wait till PLL is used as system clock source
{
}
#elif(sysclock==Low)
RCC_HCLKConfig(RCC_SYSCLK_Div2);//AHBCLK = SYSCLK/2-8Mhz/2=4Mhz
RCC_PCLK1Config(RCC_HCLK_Div1);//APB1CLK =AHBCLK-4Mhz
FLASH_SetLatency(FLASH_Latency_0);//Flash 0 wait state
RCC_SYSCLKConfig(RCC_SYSCLKSource_HSE);
#endif
}
RCC_GetClocksFreq(&RCC_ClocksStatus);
HCLK_Freq=(RCC_ClocksStatus.HCLK_Frequency/800000);
RCC_APB1PeriphClockCmd(RCC_APB1Periph_TIM2,ENABLE);//TIM2 clock enable
RCC_APB2PeriphClockCmd(RCC_APB2Periph_GPIOA | RCC_APB2Periph_GPIOB | RCC_APB2Periph_GPIOD | RCC_APB2Periph_GPIOE |
RCC_APB2Periph_AFIO, ENABLE);//Enable GPIOA, GPIOB , GPIOD , GPIIOE and AFIO clocks
RCC_APB2PeriphClockCmd(RCC_APB2Periph_GPIOA | RCC_APB2Periph_AFIO,ENABLE);//Enable GPIOD and AFIO clocks
RCC_APB1PeriphClockCmd(RCC_APB1Periph_USART3,ENABLE);//Enable USART3 clocks
}
void GPIO_Configuration(void)
{
//USART3_Tx
GPIO_InitStructure.GPIO_Pin = GPIO_Pin_10;
GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;
GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF_PP;
GPIO_Init(GPIOB, &GPIO_InitStructure);
//USART3_Rx
GPIO_InitStructure.GPIO_Pin = GPIO_Pin_11;
GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;
GPIO_InitStructure.GPIO_Mode = GPIO_Mode_IPU;
GPIO_Init(GPIOB, &GPIO_InitStructure);
//USART3_Clk
GPIO_InitStructure.GPIO_Pin = GPIO_Pin_12;
GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;
GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF_PP;
GPIO_Init(GPIOB, &GPIO_InitStructure);
}
