int fputc(int ch, FILE *p) { while((USART1->SR & 0x40)==0); USART1->DR=ch; return ch; }
时间: 2024-06-04 08:11:53 浏览: 15
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 *f) { while((USART1->SR&0X40)==0);//循环发送,直到发送完毕 USART1->DR = (u8) ch; return ch; }这段代码的含义
这段代码是对`fputc()`函数的重定义,用于将`printf()`函数中的字符通过USART1串口发送出去。下面是对代码的解释:
```c
int fputc(int ch, FILE *f) {
while((USART1->SR & 0x40) == 0); // 等待发送缓冲区为空
USART1->DR = (u8) ch; // 将字符写入USART1的数据寄存器,触发发送
return ch; // 返回发送的字符
}
```
具体解释如下:
1. `while((USART1->SR & 0x40) == 0)`:这行代码使用位掩码检查USART1的状态寄存器(SR)的第6位(TXE)是否为0,即检查发送缓冲区是否为空。如果发送缓冲区不为空,表示还有数据正在发送,需要等待。
2. `USART1->DR = (u8) ch`:将要发送的字符强制转换为8位无符号整数(u8),然后写入USART1的数据寄存器(DR)。这将触发数据的发送。
3. `return ch`:返回发送的字符。
因此,这段代码的作用是在`printf()`函数中,通过USART1串口将字符发送出去。在调用`printf()`时,每个字符都会经过这段代码进行发送,直到所有字符都被发送完毕。需要注意的是,在使用这段代码之前,需要先进行USART1串口的初始化配置。
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.