2022-04-15 15:23:17 +08:00

88 lines
2.5 KiB
C

#include "uart.h"
#include <common/kprint.h>
#define UART_MAX_BITS_RATE 115200
/**
* @brief 当前是否有数据到达
*
*/
#define serial_received(p) ((io_in8(p + 5) & 1))
/**
* @brief 当前是否有数据正等待发送
*
*/
#define is_transmit_empty(p) ((io_in8(p + 5) & 0x20))
/**
* @brief 初始化com口
*
* @param port com口的端口号
* @param bits_rate 通信的比特率
*/
int uart_init(uint32_t port, uint32_t bits_rate)
{
// 错误的比特率
if (bits_rate > UART_MAX_BITS_RATE || UART_MAX_BITS_RATE % bits_rate != 0)
return E_UART_BITS_RATE_ERROR;
io_out8(port + 1, 0x00); // Disable all interrupts
io_out8(port + 3, 0x80); // Enable DLAB (set baud rate divisor)
uint16_t divisor = E_UART_BITS_RATE_ERROR / bits_rate;
io_out8(port + 0, divisor & 0xff); // Set divisor (lo byte)
io_out8(port + 1, (divisor >> 8) & 0xff); // (hi byte)
io_out8(port + 3, 0x03); // 8 bits, no parity, one stop bit
io_out8(port + 2, 0xC7); // Enable FIFO, clear them, with 14-byte threshold
io_out8(port + 4, 0x0B); // IRQs enabled, RTS/DSR set
io_out8(port + 4, 0x1E); // Set in loopback mode, test the serial chip
io_out8(port + 0, 0xAE); // Test serial chip (send byte 0xAE and check if serial returns same byte)
// Check if serial is faulty (i.e: not same byte as sent)
if (io_in8(port + 0) != 0xAE)
{
return E_UART_SERIAL_FAULT;
}
// If serial is not faulty set it in normal operation mode
// (not-loopback with IRQs enabled and OUT#1 and OUT#2 bits enabled)
io_out8(port + 4, 0x0F);
return UART_SUCCESS;
/*
Notice that the initialization code above writes to [PORT + 1]
twice with different values. This is once to write to the Divisor
register along with [PORT + 0] and once to write to the Interrupt
register as detailed in the previous section.
The second write to the Line Control register [PORT + 3]
clears the DLAB again as well as setting various other bits.
*/
}
/**
* @brief 发送数据
*
* @param port 端口号
* @param c 要发送的数据
*/
void uart_send(uint32_t port, char c)
{
while (is_transmit_empty(port) == 0)
pause();
io_out8(port, c);
}
/**
* @brief 从uart接收数据
*
* @param port 端口号
* @return uchar 接收到的数据
*/
uchar uart_read(uint32_t port)
{
while (serial_received(port) == 0)
pause();
return io_in8(port);
}