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
}

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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.

int fputc(int ch, FILE *f) { while((USART1->SR&0X40)==0);//循环发送,直到发送完毕 USART1->DR = (u8) ch; return ch; }

这段代码是将一个字符ch通过USART1发送出去，其中USART1是一个串口设备。具体来说，代码中的USART1->SR&0X40是用来判断串口是否空闲的，如果是空闲状态，就可以将字符发送出去了。USART1->DR = (u8) ch;则是将字符写入USART1的数据寄存器中，等待发送。最后，函数返回发送出去的字符。需要注意的是，此函数需要结合其他函数一起使用，如USART1的初始化函数等。