Posted on September 03, 2012 at 09:20Hello,
I was using UART4 pin PA0 and PA1 for my project. I have done all the initialization procedures right but ended up getting junk values at the output. below is my initialization function.
void UART_LowLevel_Init(void) {
GPIO_InitTypeDef GPIO_InitStructure;
USART_InitTypeDef USART_InitStructure;
/* enable peripheral clock for USART2 */
RCC_APB1PeriphClockCmd(RCC_APB1Periph_UART4, ENABLE);
/* GPIOA clock enable */
RCC_AHB1PeriphClockCmd(RCC_AHB1Periph_GPIOA, ENABLE); //for tx,rx
//Connect GPIO pins to the UART
GPIO_PinAFConfig(GPIOA, GPIO_PinSource0 ,GPIO_AF_UART4); //Tx
GPIO_PinAFConfig(GPIOA, GPIO_PinSource1 ,GPIO_AF_UART4); //Rx
//Configure the GPIO Pins
GPIO_InitStructure.GPIO_Pin = GPIO_Pin_0 | GPIO_Pin_1;
GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF;
GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;
GPIO_InitStructure.GPIO_OType = GPIO_OType_PP;
GPIO_InitStructure.GPIO_PuPd = GPIO_PuPd_UP;
GPIO_Init(GPIOA, &GPIO_InitStructure);
//Initialize the USART
//USART_InitStructure.USART_BaudRate = 2625000; //MAximum rate for APB1 with 16 over-sampling
USART_InitStructure.USART_BaudRate = 9600;
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_Init(UART4, &USART_InitStructure);
//Enable (UE) the USART
USART_Cmd(UART4, ENABLE);
return;
}
I use USART_SendData function to send characters to the output. When I monitored the Tx line through a logic analyzer the values seem to be inverted. For example: If i send value 0x61, I get a value 0x86 at the output. This value is totally different to the value that i see in the serial monitor software in pc and it varies from time to time. Also I see a continuous output of value 0x00 in the hyperterminal even though the program is not running.
I also tried doing the below which I found in another post:
If you do not defined HSE_VALUE for the proper crystal freq it gets the default value of 25000000 Hz, irrelevant to the selected board (f.e. Discovery), see lines 90..93 in the Libraries/Device/STM32F4xx/Include/stm32f4xx.h (meaning Project Explorer).
The best way to declare the proper frequency is to set HSE_VALUE globally in Atollic IDE:
Project->Poperties->C/C++ General-> Paths and Symbols-> &sharpSymbolsPress Add.. btn, then type HSE_VALUE and in the next line type 8000000 (for Discovery).
Any help?
#wait-for-you--clive1-!-!-! #wait-for-you--clive1-!-!-! #wait-for-you--clive1-!-!-!
