Embedded Linux Learning Primer: Control LED Lights

Keep track of your Linux learning process so that you can keep going

1. Schematic analysis:

Nled_1, Nled_2, Nled_4, to the low level of the corresponding LED light, high-level corresponding to the LED light off,

s3c2440 chip Gpf4-gpf6 corresponds to Nled_1, Nled_2, Nled_4,

So the code inside the Operation GPF4-GPF6 can control led light off.

2. Know things before writing code

First step: Configure GPF0-GPF4 as output function

Step two: Control the GPF0-GPF4 output low level

3. Write code

1 . Text2 . Global _start3 _start:4 LDR R0, =0x53000000 @ Watchdog register address5             movR1, #0x06             StrR1, [r0] @ Write 0, prohibit watchdog, otherwise the CPU will continue to restart7             8Ldr sp, =1024x768*4@ set Stack, note: cannot be greater than 4k, because memory available now is only 4 K9 code in NAND Flash is moved to internal RAM after reset, this RAM is only 4 KTen BL Main @ Call the main function in C program One Halt_loop: Ab halt_loop

Refer to the Assembly section of Vedon video mimic writing, mainly for calling C language programs, preparing conditions

1 #defineGpfcon (* (volatile unsigned long *) 0x56000050)2 #defineGpfdat (* (volatile unsigned long *) 0x56000054)3 4 5 intMainvoid)6 {7UnsignedLongi =0;8 9Gpfcon =0x00001500;//set the GPF4 GPF5 GPF6 to outputTen  One      while(1) A     { -  -Gpfdat =0x00000060;//control GPF4 output low level, LED1 bright the          for(i=0; i<30000; i++);//Delay -  -Gpfdat =0x00000050;//control GPF5 output low level, LED2 bright -          for(i=0; i<30000; i++);  +  -Gpfdat =0x00000030;//control GPF6 output low level, LED4 bright +          for(i=0; i<30000; i++); A     } at      -     return 0; -}

4, compiling code, burning execution

Using GCC compilation in a Linux environment, as well as video learning to write makefile

led_test:main.c start. S arm-linux-gcc-c start. S-o start.o arm-linux-gcc-c main.c-o main.o arm0x0000000 start.o main.o-o led_test_el F arm-linux-objcopy-o binary-S led_test_elf led_test.bin arm-linux-objdump-d-m arm led_test_elf >
   
    -F *.o led_test.bin led_test_elf Led_test.dis
   

The generated led_test.bin burned to the board, observe the phenomenon, according to the expected running lights go up!

Embedded Linux Learning Primer: Control LED Lights