LED Applications of S5PV210 (Part 2)

Prepare for analysis

This time we use C language to control the LED. We need to set the stack pointer. The start.S here is like crt0.o in the helloworld program with an operating system - it is a startup code.

The stack pointer is set to 0xD003_7D80.

Resource Tools

Same as "LED Application of S5PV210 (I)"

Start writing the program

@**************************************************************************************

@File:start.S

@ Function: Use it to transfer to C program

@**************************************************************************************

.text

.global _start

_start:

ldr sp, =0xD0037D80 @ Set up the stack to call the C function

bl main @ Call the main function in the C program

halt_loop:

b halt_loop

@**************************************************************************************

/**********************************************************************************

/* File: led.c

/* Turn on LED1

/**************************************************************************************/

#define GPJ2CON (*(volatile unsigned long *) 0xE0200280)

#define GPJ2DAT (*(volatile unsigned long *) 0xE0200284)

int main()

{

GPJ2CON = 0x00000001; //Set GPJ2_O to output

GPJ2DAT = 0; // LED1 on

while(1);

return 0;

}

Makefile:

led_sp.bin: start.o led.o

arm-linux-ld -Ttext 0x0 -o ​​led_sp.elf $^

arm-linux-objcopy -O binary led_sp.elf led_sp.bin

arm-linux-objdump -D led_sp.elf > led_sp_elf.dis

gcc mkv210_image.c -o mkv210

./mkv210 led_sp.bin 210.bin

%.o : %.S

arm-linux-gcc -o $@ $< -c

%.o : %.c

arm-linux-gcc -o $@ $< -c 

clean:

rm *.o *.elf *.bin *.dis mkv210 -f

Download and run

Same as "LED Application of S5PV210 (I)"

Run Debug

The program is simple and works fine.

Remaining problem

1. Knowing that the iROM program has already initialized the watchdog, I will not implement it myself yet. I will talk about the watchdog later.