printf函数不能打印出float型变量

只看该作者 · 2017-5-23 15:19

看官网给出的例子
配置如下：
asm (".global _printf_float");
{
int i;
for (i = 0; i < len; i++)
{
UART_UartPutChar(*ptr++);
}
return(len);
}
并且heap size改为0x200后，
printf函数打印float型变量，在串口助手上不能显示，而string或者int型能正常显示。请问有解决办法吗？

只看该作者 · 2017-5-25 11:41

你可以尝试直接复制下面的代码，进行运行。
你需要把浮点型的数做一个格式转换，这样就可以通过sprintf进行输出了。
/* ========================================
*
* Copyright YOUR COMPANY, THE YEAR
* All Rights Reserved
* UNPUBLISHED, LICENSED SOFTWARE.
*
* CONFIDENTIAL AND PROPRIETARY INFORMATION
* WHICH IS THE PROPERTY OF your company.
*
* ========================================
*/
#include <project.h>
#include <stdio.h>

#if defined (__GNUC__)
/* Add an explicit reference to the floating point printf library to allow
the usage of floating point conversion specifier. */
asm (".global _printf_float");
/* For GCC compiler revise _write() function for printf functionality */
int _write(int file, char *ptr, int len)
{
int i;
for (i = 0; i < len; i++)
{
UART_UartPutChar(*ptr++);
}
return(len);
}
#elif defined(__ARMCC_VERSION)
/* For MDK/RVDS compiler revise fputc() function for printf functionality */
struct __FILE
{
int handle;
};
enum
{
STDIN_HANDLE,
STDOUT_HANDLE,
STDERR_HANDLE
};
FILE __stdin = {STDIN_HANDLE};
FILE __stdout = {STDOUT_HANDLE};
FILE __stderr = {STDERR_HANDLE};
int fputc(int ch, FILE *file)
{
int ret = EOF;
switch(file->handle)
{
case STDOUT_HANDLE:
SCB_UartPutChar(ch);
ret = ch;
break;
Document Number: 001-92486 Rev. *A Page 143 of 171
case STDERR_HANDLE:
ret = ch;
break;
default:
file = file;
break;
}
return(ret);
}
#elif defined (__ICCARM__)
/* For IAR compiler revise __write() function for printf functionality */
size_t __write(int handle, const unsigned char * buffer, size_t size)
{
size_t nChars = 0;
for (/* Empty */; size != 0; --size)
{
SCB_UartPutChar(*buffer++);
++nChars;
}
return (nChars);
}
#endif /* (__GNUC__) */

CY_ISR(UART_SCB_IRQ_Interrupt)
{
if(UART_GetRxInterruptSourceMasked() & UART_INTR_RX_NOT_EMPTY)
{
UART_UartPutString("Wel \r\n");
}

UART_SpiUartClearRxBuffer();
UART_ClearRxInterruptSource(UART_INTR_RX_NOT_EMPTY);

}

int main()
{
uint32 i = 444444444;
float f = 55.555f;
char *s;
//UART_SetCustomInterruptHandler(&MyIntHandler);

isr_StartEx(UART_SCB_IRQ_Interrupt);
UART_Start(); /* Start communication component */
CyGlobalIntEnable; /* Enable interrupts */

/* Use printf() function which will send formatted data through
* UART (SCB mode) */

UART_UartPutString("Welcome\r\n");
sprintf(s, "%10.3f", 3.1415626);

printf("Test printf function. long: %ld, float: %s \n",i,s);
for(;;)
{

}
}

只看该作者 · 2017-5-26 17:39

楼上大神指导的对，也可以参考下该链接：http://www.cypress.com/knowledge ... m-compiler-kba89724