blob: b6271c12da8f096790a6aaa259aed69720460170 (
plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
|
#include "types.h"
#include "param.h"
#include "memlayout.h"
#include "riscv.h"
#include "proc.h"
#include "spinlock.h"
#include "defs.h"
//
// qemu -machine virt has a 16550a UART
// qemu/hw/riscv/virt.c
// http://byterunner.com/16550.html
//
// caller should lock.
//
// address of one of the registers
#define R(reg) ((volatile unsigned char *)(UART0 + reg))
void
uartinit(void)
{
// disable interrupts -- IER
*R(1) = 0x00;
// special mode to set baud rate
*R(3) = 0x80;
// LSB for baud rate of 38.4K
*R(0) = 0x03;
// MSB for baud rate of 38.4K
*R(1) = 0x00;
// leave set-baud mode,
// and set word length to 8 bits, no parity.
*R(3) = 0x03;
// reset and enable FIFOs -- FCR.
*R(2) = 0x07;
// enable receive interrupts -- IER.
*R(1) = 0x01;
}
void
uartputc(int c)
{
*R(0) = c;
}
int
uartgetc(void)
{
if(*(5) & 0x01){
// input data is ready.
return *R(0);
} else {
return -1;
};
}
void
uartintr(void)
{
int c = uartgetc();
printf("%x ", c & 0xff);
}
|