一、目的
到目前為止我們所編寫的程序都是直接燒到裸板(FS2410)上運行，沒有借助操作系統(tǒng)，
如果哪個環(huán)節(jié)出錯了，就只能揣測代碼的邏輯，無法借助 GDB 調(diào)試，這無形增加了編寫代
碼的難度，如果任意時刻我們能把某個變量的值打印出來多好啊...呵呵， 你也許有同樣的
困惑，上一個實驗我們對 UART 串口編程實現(xiàn)了對超級終端接收和發(fā)送數(shù)據(jù)，也許我們可以
編寫一個類似 C 語言里的 printf，作用就是向上位機的超級終端發(fā)送我們指定的任何數(shù)據(jù)。
懷著這樣美好的愿望，隨我一起踏上征程吧。
二、代碼
很多代碼是在前面幾個實驗的基礎上進行整理復用之，更多細節(jié)請參考前面隨筆，這里
僅附簡略注解。
@ 文件 head.s
@ 作用:關閉看門狗、SDRAM 的初始化設置、搬移 Nand Flash 4K 以后
@ 的代碼到 SDRAM 的指定位置、執(zhí)行 SDRAM 中的代碼
.text
.global _start
_start:
ldr r0, =0x53000000 @ Close Watch Dog Timer
mov r1, #0x0
str r1, [r0]
bl memory_setup @ Initialize memory setting
bl flash_to_sdram @ Copy code to sdram
ldr sp, =0x34000000 @ Set stack pointer
ldr pc, =main @ execute the code in SDRAM
@ 文件 mem.s
@ 作用:SDRAM 的初始化設置
@ 關于初始化的更多細節(jié)，請參考我前面的隨筆
.global memory_setup
memory_setup:
mov r1, #0x48000000
adrl r2, mem_cfg_val
add r3, r1, #13*4
1:
@ write initial values to registers
ldr r4, [r2], #4
str r4, [r1], #4
cmp r1, r3
bne 1b
mov pc, lr
.align 4
mem_cfg_val:
.long 0x22111110 @ BWSCON
.long 0x00000700 @ BANKCON0
.long 0x00000700 @ BANKCON1
.long 0x00000700 @ BANKCON2
.long 0x00000700 @ BANKCON3
.long 0x00000700 @ BANKCON4
.long 0x00000700 @ BANKCON5
.long 0x00018005 @ BANKCON6
.long 0x00018005 @ BANKCON7 9bit
.long 0x008e07a3 @ REFRESH
.long 0x000000b2 @ BANKSIZE
.long 0x00000030 @ MRSRB6
.long 0x00000030 @ MRSRB7
@ 文件 flash.s
@ 作用:設置 Nand Flash 的控制寄存器、讀取 Nand Flash
@ 中的代碼到 SDRAM 的指定位置，更多細節(jié)請參考我前面的隨筆
.equ NFCONF, 0x4e000000
.equ NFCMD, 0x4e000004
.equ NFADDR, 0x4e000008
.equ NFDATA, 0x4e00000c
.equ NFSTAT, 0x4e000010
.equ NFECC, 0x4e000014
.global flash_to_sdram
flash_to_sdram:
@ Save return addr
mov r10,lr
@ Initialize Nand Flash
mov r0,#NFCONF
ldr r1,=0xf830
str r1,[r0]
@ First reset and enable Nand Flash
ldr r1,[r0]
bic r1, r1, #0x800
str r1,[r0]
ldr r2,=NFCMD
mov r3,#0xff
str r3,[r2]
@ for delay
mov r3, #0x0a
1:
subs r3, r3, #1
bne 1b
@ Wait until Nand Flash bit0 is 1
wait_nfstat:
ldr r2,=NFSTAT
ldr r3,[r2]
tst r3,#0x01
beq wait_nfstat
@ Disable Nand Flash
ldr r0,=NFCONF
ldr r1,[r0]
orr r1,r1,#0x8000
str r1,[r0]
@ Initialzie stack
ldr sp,=4096
@ Set arguments and call
@ function nand_read defined in nand_read.c
ldr r0,=0x30000000
mov r1,#0
mov r2,#1024*40
bl nand_read
@ return
mov pc,r10
/* 文件 nand_read.c
* 作用:從 Nand Flash 中讀取一塊數(shù)據(jù)到 SDRAM 中的指定位置
*/
#define NFCONF (*(volatile unsigned long *)0x4e000000)
#define NFCMD (*(volatile unsigned long *)0x4e000004)
#define NFADDR (*(volatile unsigned long *)0x4e000008)
#define NFDATA (*(volatile unsigned long *)0x4e00000c)
#define NFSTAT (*(volatile unsigned long *)0x4e000010)
#define NFECC (*(volatile unsigned long *)0x4e000014)
#define NAND_SECTOR_SIZE 512
#define NAND_BLOCK_MASK 0x1ff
void wait_idle() {
int i;
for (i = 0; i < 50000; ++i) ;
}
int nand_read(unsigned char *buf, unsigned long start_addr, int size){
int i, j;
/*
* detect the argument
*/
if ((start_addr & NAND_BLOCK_MASK) || (size & NAND_BLOCK_MASK)) {
return -1;
}
/* chip Enable */
NFCONF &= ~0x800;
for (i=0; i<10; i++) {
;
}
for (i=start_addr; i < (start_addr + size); i+=NAND_SECTOR_SIZE) {
NFCMD = 0;
/* Write Address */
NFADDR = i & 0xff;
NFADDR = (i >> 9) & 0xff;
NFADDR = (i >> 17) & 0xff;
NFADDR = (i >> 25) & 0xff;
wait_idle();
for(j=0; j < NAND_SECTOR_SIZE; j++) {
*buf++ = (NFDATA & 0xff);
}
}
NFCONF |= 0x800; /* chip disable */
return 0;
}
/* 頭文件 serl.h
* 作用:定義相關寄存器、UART 初始化函數(shù)聲明、串口讀寫函數(shù)的聲明
*/
#ifndef __SERL_H__
#define __SERL_H__
#define GPHCON (*(volatile unsigned long *)0x56000070)
/* PORT PULL-UP REGISTER*/
#define GPHUP (*(volatile unsigned long *)0x56000078)
/* UART FIFO control register 0*/
#define UFCON0 (*(volatile unsigned long *)0x50000008)
/* UART line control register 0*/
#define ULCON0 (*(volatile unsigned long *)0x50000000)
/* UART CONTROL REGISTER 0*/
#define UCON0 (*(volatile unsigned long *)0x50000004)
/* UART modem control register 0*/
#define UMCON0 (*(volatile unsigned long *)0x5000000C)
/* UART baud rate divisor register 0*/
#define UBRDIV0 (*(volatile unsigned long *)0x50000028)
/* UART TX/RX STATUS REGISTER 0*/
#define UTRSTAT0 (*(volatile unsigned long *)0x50000010)
#define UTXH0 (*(volatile unsigned char *)0x50000020)
#define URXH0 (*(volatile unsigned char *)0x50000024)
#define TXD0_READY 0x2
#define RXD0_READY 0x1
void init_uart();
unsigned char uart_getc();
void uart_putc(unsigned char ch);
void uart_puts(unsigned char* src);
#endif
/* 文件 serl.c*/
#include "serl.h"
void init_uart() {
GPHCON |= 0xa0; /* GPH2, GPH3 used as RXD0, TXD0*/
GPHUP = 0x0c; /* GPH2, GPH3 poll-up */
ULCON0 = 0x03; /* normal mode, no parity, one stop bit, 8-bit*/
UCON0 = 0x05; /* Loopback mode*/
UFCON0 = 0x00; /* not use FIFO*/
UMCON0 = 0x00; /* disable flow control*/
UBRDIV0 = 12; /* baud rate 57600*/
}
void uart_putc(unsigned char ch) {
while (!(UTRSTAT0 & TXD0_READY));
UTXH0 = ch;
}
unsigned char uart_getc(){
while (! (UTRSTAT0 & RXD0_READY));
return URXH0;
}
void uart_puts(unsigned char* src) {
unsigned char *p = src;
while (*p != '\0') {
if (*p == 0x0a)
uart_putc(0x0d);
uart_putc(*p);
p++;
}
}
/*
* 頭文件 printf.h
* 作用:對外提供調(diào)用接口 uart_printf
*/
#ifndef __PRINTF_HH__
#define __PRINTF_HH__
void uart_printf(char *fmt, ...);
#endif
/*
* 文件 printf.c
* 文件中大部分代碼來自 linux 0.11 內(nèi)核的 vsprintf.c， 只是作了相應的刪減，
* <<Linux 內(nèi)核完全注釋>> 上有更詳細的解釋
*/
#include <stdarg.h>
#include <linux/types.h>
#include <linux/ctype.h>
#include "printf.h"
#include "serl.h"
#define ZEROPAD 1 /* pad with zero */
#define SIGN 2 /* unsigned/signed long */
#define PLUS 4 /* show plus */
#define SPACE 8 /* space if plus */
#define LEFT 16 /* left justified */
#define SPECIAL 32 /* 0x */
#define LARGE 64 /* use 'ABCDEF' instead of 'abcdef' */
#define is_digit(c) ((c) >= '0' && (c) <= '9')
#define do_div(n,base) ({ \
int __res; \
__res = ((unsigned long) n) % (unsigned) base; \
n = ((unsigned long) n) / (unsigned) base; \
__res; })
static unsigned char sprint_buf[1024];
int strnlen(const char * s, int count)
{
const char *sc;
for (sc = s; count-- && *sc != '\0'; ++sc)
/* nothing */;
return sc - s;
}
unsigned char _ctype[] = {
_C,_C,_C,_C,_C,_C,_C,_C, /* 0-7 */
_C,_C|_S,_C|_S,_C|_S,_C|_S,_C|_S,_C,_C, /* 8-15 */
_C,_C,_C,_C,_C,_C,_C,_C, /* 16-23 */
_C,_C,_C,_C,_C,_C,_C,_C, /* 24-31 */
_S|_SP,_P,_P,_P,_P,_P,_P,_P, /* 32-39 */
_P,_P,_P,_P,_P,_P,_P,_P, /* 40-47 */
_D,_D,_D,_D,_D,_D,_D,_D, /* 48-55 */
_D,_D,_P,_P,_P,_P,_P,_P, /* 56-63 */
_P,_U|_X,_U|_X,_U|_X,_U|_X,_U|_X,_U|_X,_U, /* 64-71 */
_U,_U,_U,_U,_U,_U,_U,_U, /* 72-79 */
_U,_U,_U,_U,_U,_U,_U,_U, /* 80-87 */
_U,_U,_U,_P,_P,_P,_P,_P, /* 88-95 */
_P,_L|_X,_L|_X,_L|_X,_L|_X,_L|_X,_L|_X,_L, /* 96-103 */
_L,_L,_L,_L,_L,_L,_L,_L, /* 104-111 */
_L,_L,_L,_L,_L,_L,_L,_L, /* 112-119 */
_L,_L,_L,_P,_P,_P,_P,_C, /* 120-127 */
0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0, /* 128-143 */
0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0, /* 144-159 */
_S|_SP,_P,_P,_P,_P,_P,_P,_P,_P,_P,_P,_P,_P,_P,_P,_P, /* 160-175 */
_P,_P,_P,_P,_P,_P,_P,_P,_P,_P,_P,_P,_P,_P,_P,_P, /* 176-191 */
_U,_U,_U,_U,_U,_U,_U,_U,_U,_U,_U,_U,_U,_U,_U,_U, /* 192-207 */
_U,_U,_U,_U,_U,_U,_U,_P,_U,_U,_U,_U,_U,_U,_U,_L, /* 208-223 */
_L,_L,_L,_L,_L,_L,_L,_L,_L,_L,_L,_L,_L,_L,_L,_L, /* 224-239 */
_L,_L,_L,_L,_L,_L,_L,_P,_L,_L,_L,_L,_L,_L,_L,_L}; /* 240-255 */
static int skip_atoi(const char **s)
{
int i=0;
while (is_digit(**s))
i = i*10 + *((*s)++) - '0';
return i;
}
static char * number(char * str, long num, int base, int size, int precision
,int type)
{
char c,sign,tmp[66];
const char *digits="0123456789abcdefghijklmnopqrstuvwxyz";
int i;
if (type & LARGE)
digits = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ";
if (type & LEFT)
type &= ~ZEROPAD;
if (base < 2 || base > 36)
return 0;
c = (type & ZEROPAD) ? '0' : ' ';
sign = 0;
if (type & SIGN) {
if (num < 0) {
sign = '-';
num = -num;
size--;
} else if (type & PLUS) {
sign = '+';
size--;
} else if (type & SPACE) {
sign = ' ';
size--;
}
}
if (type & SPECIAL) {
if (base == 16)
size -= 2;
else if (base == 8)
size--;
}
i = 0;
if (num == 0)
tmp[i++]='0';
else while (num != 0)
tmp[i++] = digits[do_div(num,base)];
if (i > precision)
precision = i;
size -= precision;
if (!(type&(ZEROPAD+LEFT)))
while(size-->0)
*str++ = ' ';
if (sign)
*str++ = sign;
if (type & SPECIAL) {
if (base==8)
*str++ = '0';
else if (base==16) {
*str++ = '0';
*str++ = digits[33];
}
}
if (!(type & LEFT))
while (size-- > 0)
*str++ = c;
while (i < precision--)
*str++ = '0';
while (i-- > 0)
*str++ = tmp[i];
while (size-- > 0)
*str++ = ' ';
return str;
}
int __vsprintf(char *buf, const char *fmt, va_list args)
{
int len;
unsigned long num;
int i, base;
char * str;
const char *s;
int flags; /* flags to number() */
int field_width; /* width of output field */
int precision; /* min. # of digits for integers; max number of chars for from string */
int qualifier; /* 'h', 'l', or 'L' for integer fields */
for (str=buf ; *fmt ; ++fmt) {
if (*fmt != '%') {
*str++ = *fmt;
continue;
}
/* process flags */
flags = 0;
repeat:
++fmt; /* this also skips first '%' */
switch (*fmt) {
case '-': flags |= LEFT; goto repeat;
case '+': flags |= PLUS; goto repeat;
case ' ': flags |= SPACE; goto repeat;
case '#': flags |= SPECIAL; goto repeat;
case '0': flags |= ZEROPAD; goto repeat;
}
/* get field width */
field_width = -1;
if (is_digit(*fmt))
field_width = skip_atoi(&fmt);
else if (*fmt == '*') {
++fmt;
/* it's the next argument */
field_width = va_arg(args, int);
if (field_width < 0) {
field_width = -field_width;
flags |= LEFT;
}
}
/* get the precision */
precision = -1;
if (*fmt == '.') {
++fmt;
if (is_digit(*fmt))
precision = skip_atoi(&fmt);
else if (*fmt == '*') {
++fmt;
/* it's the next argument */
precision = va_arg(args, int);
}
if (precision < 0)
precision = 0;
}
/* get the conversion qualifier */
qualifier = -1;
if (*fmt == 'h' || *fmt == 'l' || *fmt == 'L') {
qualifier = *fmt;
++fmt;
}
/* default base */
base = 10;
switch (*fmt) {
case 'c':
if (!(flags & LEFT))
while (--field_width > 0)
*str++ = ' ';
*str++ = (unsigned char) va_arg(args, int);
while (--field_width > 0)
*str++ = ' ';
continue;
case 's':
s = va_arg(args, char *);
if (!s)
s = "<NULL>";
len = strnlen(s, precision);
if (!(flags & LEFT))
while (len < field_width--)
*str++ = ' ';
for (i = 0; i < len; ++i)
*str++ = *s++;
while (len < field_width--)
*str++ = ' ';
continue;
case 'p':
if (field_width == -1) {
field_width = 2*sizeof(void *);
flags |= ZEROPAD;
}
str = number(str,
(unsigned long) va_arg(args, void *), 16, field_width, precision, flags);
continue;
case 'n':
if (qualifier == 'l') {
long * ip = va_arg(args, long *);
*ip = (str - buf);
} else {
int * ip = va_arg(args, int *);
*ip = (str - buf);
}
continue;
/* integer number formats - set up the flags and "break" */
case 'o':
base = 8;
break;
case 'X':
flags |= LARGE;
case 'x':
base = 16;
break;
case 'd':
case 'i':
flags |= SIGN;
case 'u':
break;
default:
if (*fmt != '%')
*str++ = '%';
if (*fmt)
*str++ = *fmt;
else
--fmt;
continue;
}
if (qualifier == 'l')
num = va_arg(args, unsigned long);
else if (qualifier == 'h') {
num = (unsigned short) va_arg(args, int);
if (flags & SIGN)
num = (short) num;
} else if (flags & SIGN)
num = va_arg(args, int);
else
num = va_arg(args, unsigned int);
str = number(str, num, base, field_width, precision, flags);
}
*str = '\0';
return str-buf;
}
/* 這就我們的 printf, 注意我們將參數(shù)輸出到串口 UART0，而非標準輸出*/
void uart_printf(char *fmt, ...)
{
va_list args;
va_start(args, fmt);
__vsprintf(sprint_buf, fmt,args);
va_end(args);
/* 將緩沖區(qū)的字符輸出到串口*/
uart_puts(sprint_buf);
}
/*
* 文件 main.c
* 作用:測試代碼
*/
#include "serl.h"
#include "printf.h"
#define GPFCON (*(volatile unsigned long *)0x56000050)
#define GPFDAT (*(volatile unsigned long *)0x56000054)
int main()
{
int a = 10;
init_uart();
/*
* 調(diào)用我們自己的 uart_printf，將數(shù)據(jù)輸出到串口,稍后你將
* 在超級終端上看到顯示結果。之所以不叫 printf 是為了不與
* arm-linux-gcc 的庫函數(shù) printf 相沖突
*/
uart_printf("Hello,Embeded!\n");
uart_printf("%d\n",a);
return 0;
}
最后要說的是 Makefile，這個Makefile 在前面 Makefile的基礎上作了很大的改進，
它不需要你再指定源文件，而是在當前目錄下讀取擴展名為 .s 和 .c 的文件作為輸入文件，
你只需指定最終要生成的可執(zhí)行文件即可，只是它還是不太完美, 你還要指定它依賴的目標文
件，因為 head.o mem.o flash.o nand_read.o 這些文件被連接生成可執(zhí)行文件后它
們的代碼必須位于前 4K， 這樣才能保證它們自動被 ARM 加載，從而設置堆棧、初始化內(nèi)存、
讀取 Nand Flash 的代碼完成自身到 SDRAM 的 self-copying。將來我們會用連接腳本
來解決這個問題。
# Makefile for compiling ARM program
# Author: Jianbin Wang
CC=arm-linux-gcc
CFLAGS=-Wall -g -c
LD=arm-linux-ld
LDFLAGS:=$(LDFLAGS) -Ttext 0x30000000
INCLUDES=-I./
CFLAGS:=$(CFLAGS) $(INCLUDES)
LIBS=-lgcc -L/usr/local/arm/3.3.2/lib/gcc-lib/arm-linux/3.3.2
CONVERT=arm-linux-objcopy
CVFLAGS=-O binary -S
RM=rm -f
SRCDIRS=.
TARGET=main
TMPOBJ=$(TARGET)_tmp.o
SRCS=$(foreach dir,$(SRCDIRS),$(wildcard $(dir)/*.c $(dir)/*.s))
OBJS=head.o mem.o flash.o nand_read.o main.o printf.o serl.o
all:$(TARGET)
$(TARGET):$(OBJS)
$(LD) $(LDFLAGS) -o $(TMPOBJ) $(OBJS) $(LIBS)
$(CONVERT) $(CVFLAGS) $(TMPOBJ) $(TARGET)
$(OBJS):$(SRCS)
$(CC) $(CFLAGS) $(SRCS)
clean:
$(RM) $(TARGET)
$(RM) $(TMPOBJ)
$(RM) $(OBJS)
三、編譯、燒寫、測試
Make 一下就會生成我們要的文件 main, 將其通過 JTAG 燒入 Nand Flash。用超級終
連接到開發(fā)板，注意波特率設為 57600，數(shù)據(jù)位 8，無奇偶校正，停止位1，無數(shù)據(jù)流控制。現(xiàn)
在 Reset 一下的開發(fā)板，然后靜靜的等待吧，生成的二進制文件 main 有 39K 大呢，要等它
完全復制到 SDRAM 至少要兩三分鐘...之后，在超級終端上是不是出現(xiàn)了字符串:
Hello,Embeded!
10
呵呵，至此我們的愿望變現(xiàn)實，是不是很不可思議 :-)