int fputc(int ch, FILE *f) { while((USART2->SR&0X40)==0){}//循环发送,直到发送完毕 USART2->DR = (u8) ch; return ch; }

这段代码是一个用于重定向 printf 函数输出到串口的函数。函数名为 fputc，接受两个参数，一个是要输出的字符 ch，另一个是文件指针 f，这里并没有使用文件指针，所以可以将其忽略。函数体中使用了一个 while 循环来等待 USART2 发送寄存器的状态位 TXE 为 1，表示 USART2 发送寄存器为空，可以发送数据了。然后将要输出的字符 ch 转换成一个 u8 类型的数据，并通过 USART2 发送寄存器 DR 发送出去。最后，函数返回输出的字符 ch。在重定向 printf 输出到串口时，需要在 main 函数中使用 freopen 函数将 stdout 重定向到 fputc 函数，例如：freopen("USART2", "w", stdout)。

相关问题

int fputc(int ch, FILE *p) { while((USART1->SR & 0x40)==0); USART1->DR=ch; return ch; }

int fputc(int ch, FILE *p) {
while((USART1->SR & 0x20) == 0); // wait until transmit data register is empty
USART1->DR = (uint8_t) ch; // send the character to the USART data register
return ch; // return the character sent
}

int fputc(int ch, FILE *p) { while((USART1->SR & 0x40)==0); USART1->DR=ch; return ch; }作用

& 0x80) == 0); USART1->DR = (ch & 0xFF); return ch; }

This is a function that writes a single character (represented by the integer "ch") to a file (represented by the pointer "p") using USART1 (a Universal Synchronous/Asynchronous Receiver/Transmitter).

The function first checks the status register (SR) of USART1 to see if it is ready to transmit data. It does this by checking if the transmit data register is empty (the 7th bit of the SR is set to 1).

If the transmit data register is not empty, the function waits in a loop until it is (by repeatedly checking the SR). Once the transmit data register is empty, the function writes the character to the data register (DR) of USART1, which is then transmitted over the UART.

Finally, the function returns the character that was written to the file.