Sysclk and USB prescaler Confusion

Also as USBPRE is stated as: 'PLL clock is divided by 1' which means 72 Mhz (as PLL is configured as 72 Mhz), but why USB clock is shown as 48 Mhz?

Thank you for the reply and for your help.

I have no idea what your processing consists of, but the chip looks to be running at 72 MHz.

My processing is with the line scan camera. 128 bytes are coming at 2kHz and so the conversion of analog to digital is done through ADC and DMA. The values stored at some array from DMA is processed in main function. So the input and the output rate of data is drastically different. This is the problem.

Any of the USART will suffice, under Keil easy enough to redirect/retarget printf() to which ever port you want, or to just write some serial output debug routines. Used USART1, and USART3, for debug console in the past.

For USART;

For USART;

/******************************************************************************/
void USART_Configuration(void)
{
GPIO_InitTypeDef GPIO_InitStructure;
USART_InitTypeDef USART_InitStructure;
RCC_APB2PeriphClockCmd(RCC_APB2Periph_GPIOA, ENABLE);
/* Configure USART Tx as alternate function push-pull */
GPIO_InitStructure.GPIO_Pin = GPIO_Pin_9; // PA.09 USART1.TX
GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF_PP;
GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;
GPIO_Init(GPIOA, &GPIO_InitStructure);
/* Configure USART Rx as input floating */
GPIO_InitStructure.GPIO_Pin = GPIO_Pin_10; // PA.10 USART1.RX
GPIO_InitStructure.GPIO_Mode = GPIO_Mode_IN_FLOATING;
GPIO_Init(GPIOA, &GPIO_InitStructure);
/* USART resources configuration (Clock, GPIO pins and USART registers) ----*/
/* USART 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;
/* Enable UART clock */
RCC_APB2PeriphClockCmd(RCC_APB2Periph_USART1, ENABLE);
/* USART configuration */
USART_Init(USART1, &USART_InitStructure);
/* Enable the USART1 */
USART_Cmd(USART1, ENABLE);
}
/******************************************************************************/
#include <
stdio.h
>
#include <
rt_misc.h
>
#pragma import(__use_no_semihosting_swi)
struct __FILE { int handle; /* Add whatever you need here */ };
FILE __stdout;
FILE __stdin;
int sendchar(char c)
{
while((USART1->SR & 0x80)==0); // 80 = TXE, 40 = TC
USART1->DR = c;
return(1);
}
int getkey(void)
{
while((USART1->SR & 0x20)==0); // 20 = RXNE
return(USART1->DR);
}
int fputc(int ch, FILE *f)
{
if ((char)ch == '
')
sendchar('
');
return (sendchar((char)ch));
}
int fgetc(FILE *f) {
return (getkey());
}
int ferror(FILE *f) {
/* Your implementation of ferror */
return EOF;
}
void _ttywrch(int ch)
{
if ((char)ch == '
')
sendchar('
');
sendchar((char)ch);
}
void _sys_exit(int return_code) {
label: goto label; /* endless loop */
}
/**************************************************************************************/

I am limited to use Ride7 based upon the board, emulator (programmer) i am using and hence i was referencing the examples.

Thanks, now it is not a problem.