开发环境：

系统：Ubuntu 10.04.4

单板：micro2440

编译器：arm-linux-gcc-4.3.2

搭建开发环境详见Ubuntu 10.04.4开发环境配置。http://www.linuxidc.com/Linux/2013-04/83609.htm

目标：实现micro2440单板上4个led灯闪烁

第一个程序很简单，用汇编实现。硬件如下：

nLED_1——>GPB5

nLED_2——>GPB6

nLED_3——>GPB7

nLED_4——>GPB8

根据s3c2440手册编写代码，包括2个文件1_led.s和Makefile.

文件·1_led.s：

.text
.global _start
_start: 
 ldr r0,=0x56000010
 mov r1,#0x00015400
 str r1,[r0]
 ldr r0,=0x56000014
loop: mov r1,#0x00000000
 str r1,[r0]
 bl delay
 mov r1,#0x00000ff0
 str r1,[r0]
 bl delay
 b loop

delay:
 mov r4,#100
del1: mov r5,#1000
del2: sub r5,r5,#1
 nop
 cmp r5,#1
 bne del2
 sub r4,r4,#1
 nop
 cmp r4,#1
 bne del1
 mov pc,lr

文件Makefile:

1_led.bin:1_led.s
 arm-linux-gcc -g -c -o 1_led.o 1_led.s
 arm-linux-ld -Ttext 0x00000000 -g 1_led.o -o 1_led_elf
 arm-linux-objcopy -O binary -S 1_led_elf 1_led.bin
 arm-linux-objdump -D 1_led_elf > 1_led.dis
clean:
 rm -f 1_led.bin *.o 1_led_elf 1_led.dis

linuxidc@linuxidc:~$ cd /home/linuxidc/Si/micro2440/1_led/
 
linuxidc@linuxidc:~/Si/micro2440/1_led$ make
 arm-linux-gcc -g -c -o 1_led.o 1_led.s
 arm-linux-ld -Ttext 0x00000000 -g 1_led.o -o 1_led_elf
 arm-linux-objcopy -O binary -S 1_led_elf 1_led.bin
 arm-linux-objdump -D 1_led_elf > 1_led.dis
 linuxidc@linuxidc:~/Si/micro2440/1_led$ ls
 1_led.bin  1_led.dis  1_led_elf  1_led.o  1_led.s  Makefile

烧写、测试：
 
很多人电脑都没有并口或者openjtag编程器，这里介绍直接用u-boot烧写。前提是单板已有u-boot并且支持网卡。
 
我用NOR Flash里的u-boot烧写程序到NAND Flash,过程如下：
 
单板NOR Flash启动上电：

U-Boot 2012.04.01 (Oct 25 2012 - 22:47:25)

CPUID: 32440001
FCLK:      400 MHz
HCLK:      100 MHz
PCLK:      50 MHz
DRAM:  64 MiB
WARNING: Caches not enabled
Flash: 2 MiB
NAND:  256 MiB
In:    serial
Out:  serial
Err:  serial
Net:  dm9000
Warning: dm9000 MAC addresses don't match:
Address in SROM is        ff:ff:ff:ff:ff:ff
Address in environment is  00:0c:29:4d:e4:f4

Hit any key to stop autoboot:  0
SMDK2410 # printenv
baudrate=115200
bootargs=console=ttySAC0 root=/dev/mtdblock3
bootcmd=nand read 30000000 kernel;bootm 30000000
bootdelay=5
ethact=dm9000
ethaddr=00:0c:29:4d:e4:f4
gatewayip=172.16.1.1
ipaddr=172.16.1.133
mtddevname=u-boot
mtddevnum=0
mtdids=nand0=micro2440-0
mtdparts=mtdparts=micro2440-0:256k(u-boot),128k(params),2M(kernel),-(rootfs)
netmask=255.255.255.0
partition=nand0,0
serverip=172.16.1.135
stderr=serial
stdin=serial
stdout=serial

Environment size: 476/131068 bytes
SMDK2410 # tftp 0x30000000 1_led.bin
dm9000 i/o: 0x20000000, id: 0x90000a46
DM9000: running in 16 bit mode
MAC: 00:0c:29:4d:e4:f4
could not establish link
Using dm9000 device
TFTP from server 172.16.1.135; our IP address is 172.16.1.133
Filename '1_led.bin'.
Load address: 0x30000000
Loading: #
done
Bytes transferred = 96 (60 hex)
SMDK2410 # nand erase 0 0x40000

NAND erase: device 0 offset 0x0, size 0x40000
Erasing at 0x20000 -- 100% complete.
OK
SMDK2410 # nand write 0x30000000 0 0x40000

NAND write: device 0 offset 0x0, size 0x40000
 262144 bytes written: OK
SMDK2410 # 

注意printenv发现网卡参数不对，需要设置如下：
 
SMDK2410 # set ipaddr 172.16.1.133
 SMDK2410 # set gatewayip 172.16.1.1
 SMDK2410 # set serverip 172.16.1.135
 SMDK2410 # save
 
接着单板断电，拨到NAND Flash启动，上电，4个LED灯就开始闪烁。