f769uart寄存器版本

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f769uart寄存器版本 [复制链接]

书接上回的寄存器配置io口的输出，今天开始寄存器版本的uart配置。

首先看datasheet2.25关于usart的说明   page42
The USART peripheral supports:
• Full-duplex asynchronous communications
• Configurable oversampling method by 16 or 8 to give flexibility between speed and
clock tolerance
• Dual clock domain allowing convenient baud rate programming independent from the
PCLK reprogramming
• A common programmable transmit and receive baud rate of up to 27 Mbit/s when the
USART clock source is system clock frequency (max is 216 MHz) and oversampling by
8 is used.
• Auto baud rate detection
• Programmable data word length (7 or 8 or 9 bits) word length
• Programmable data order with MSB-first or LSB-first shifting
• Progarmmable parity (odd, even, no parity)
• Configurable stop bits (1 or 1.5 or 2 stop bits)
• Synchronous mode and clock output for synchronous communications
• Single-wire half-duplex communications
• Separate signal polarity control for transmission and reception
• Swappable Tx/Rx pin configuration
• Hardware flow control for modem and RS-485 transceiver
• Multiprocessor communications
• LIN master synchronous break send capability and LIN slave break detection capability
• IrDA SIR encoder decoder supporting 3/16 bit duration for normal mode
• Smartcard mode ( T=0 and T=1 asynchronous protocols for Smartcards as defined in
the ISO/IEC 7816-3 standard )
• Support for Modbus communication  
目前几乎所有的uart应用都不涉及flow控制，所以本次评测也不做这方面的工作。
从原理图可知，discovery的板子上最容易配置的是usart6，于是我们就配置usart6的功能。

有图可知，占用PC6，PC7这2个IO口。
首先要设置IO的功能。
        RCC->AHB1ENR |= 0x04;
        GPIOC->AFR[0] = 0;
        GPIOC->AFR[0] = 0x88000000;
        GPIOC->MODER &= ~((3 << 6) | (3 << 7));
        GPIOC->MODER |= (2 << 6) | (2 << 7);
        GPIOC->OSPEEDR &= ~((3 << 6) | (3 << 7));
        GPIOC->OSPEEDR |= (3 << 6) | (3 << 7);
        GPIOC->OTYPER = ~((1 << 6) | (1 << 7));
        GPIOC->PUPDR &= ~((3 << 6) | (3 << 7));
        GPIOC->PUPDR |= (1 << 6) | (1 << 7);
然后开始配置uart的功能
RCC->APB2ENR |= 0x20;
        //reset usart6
        RCC->APB2RSTR |= (RCC_APB2RSTR_USART6RST);
        RCC->APB2RSTR &= ~(RCC_APB2RSTR_USART6RST);
        USART6->CR1 &=  ~USART_CR1_UE;//Disable UART
        USART6->CR1 = 0x0U;
        USART6->CR2 = 0x0U;
        USART6->CR3 = 0x0U;
        
        
        
        USART6->CR1 |= (0 << 28) | (0 << 12);
        USART6->BRR=0x3aa; //115200
        
        USART6->CR1 |= 0x0d << 0;


增加一个发送函数
void usart6_send(uint8_t data)
{
        USART6->TDR=data;
        while((USART6->ISR&0X40)==0);//等待发送结束
}








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