Imx6ull bare metal development learning 1-assembly lit LED

adopt GNU ARM Assembly implementation is right led Light flashing control .

Programming environment building :

Development board : Wildfire Imx6ull mini plate

Programming environment :Ubuntu18.04         +          VScode

Assemble the code directly :

/*******************
* file name :    led.s
* author     :      Guizhiwei 
* mailbox     ：  [email protected]
* describe     ： Bare metal experimental test 1  Assembly light up led The lamp 
 ********************/

 .global    _start      @ Global label 

 /*****
 * describe  : _start function 
  */
  _start :

  /*****
  * Lighten up LED The lamp  GPIO5_IO03
  * Open drain output 
  */

  /*****
  *1. Enable to control the clock 
   */
ldr r0, =0x020c4068      @ Configuration register CCM_CCGR0
ldr r1, =0xffffffff
str r1, [r0]

ldr r0, =0x020c406C      @ Configuration register CCM_CCGR1
ldr r1, =0xffffffff
str r1, [r0]

ldr r0, =0x020c4070      @ Configuration register CCM_CCGR2
ldr r1, =0xffffffff
str r1, [r0]

ldr r0, =0x020c4074      @ Configuration register CCM_CCGR3
ldr r1, =0xffffffff
str r1, [r0]

ldr r0, =0x020c4078      @ Configuration register CCM_CCGR4
ldr r1, =0xffffffff
str r1, [r0]

ldr r0, =0x020c407C      @ Configuration register CCM_CCGR5
ldr r1, =0xffffffff
str r1, [r0]

ldr r0, =0x020c4080      @ Configuration register CCM_CCGR6
ldr r1, =0xffffffff
str r1, [r0]

  /*****
  *2.GPIO5_IO03  Reuse function configuration GPIO
  *IOMUXC_SNVS_SW_MUX_CTL_PAD_SNVS_TAMPER3  Address 229_0014h
   */
ldr r0, =0x02290014      @ Configuration register SNVS_TAMPER3
ldr r1, =0x5                        @AL5
str r1, [r0]

  /*****
  *3.GPIO5_IO03  To configure IO Property function 
  *IOMUXC_SNVS_SW_PAD_CTL_PAD_SNVS_TAMPER3  Address  229_0058h
  *BIT0  Swaying rate  0- Slow down 
  *BIT5-3  Driving ability R0/6  -110
  *BIT7-6  Speed  100mhz-10
  * BIT11  Open drain output enable  1- Turn on 
  *BIT12  The pull-down function is enabled  0- Close the pull-down button 
  *BIT13  Keep function 0
  *BIT15-14 100K Up and down resistance  -00
  *BIT16 hys-0 close 
  * Set the configuration value :8B0-100010110000
   */
ldr r0, =0x02290058      @ Configuration register SNVS_TAMPER3
ldr r1, =0x08B0                @AL5
str r1, [r0]

/*****
*4. Set up GPIO5_IO03  For export 
*GPIO5_GDIR    Address 20A_C004
*GPIO5_DR        Address 20A_C000
*/
ldr r0, =0x020AC004      @ Configuration register GPIO5_GDIR
ldr r1, =0x08                    @BIT3
str r1, [r0]

/*****
*5 open GPIO LED
*/
ldr r0, =0x020AC000      @GPIO5_DR
ldr r1, =0x00                     @BIT3
str r1, [r0]

/*****
*6 loop Cycling 
*/
loop:
   /**
   * turn on the light 
    */
   ldr r0, =0x020AC000      @GPIO5_DR
   ldr r1, =0x00                     @BIT3
   str r1, [r0]

   /**
   * Time delay 
    */
   bl delay

   /**
   * Turn off the lights 
    */
   ldr r0, =0x020AC000      @GPIO5_DR
   ldr r1, =0x08                     @BIT3
   str r1, [r0]

   /**
   * Time delay 
    */
   bl delay

    b loop

/**
 * Time delay 
*/
delay:
   ldr r2, =0xfffff
   ldr r3, =0x0
delay_loop:
   sub r2,r2, #1
   cmp r2,r3
   bne delay_loop
   mov pc,lr      @ Return the main function 

A simplified version of makefie

led.bin : led.s
	arm-linux-gnueabihf-gcc -g -c led.s -o led.o
	arm-linux-gnueabihf-ld -Ttext 0x87800000 led.o -o led.elf
	arm-linux-gnueabihf-objcopy -O binary -S -g led.elf led.bin

clean:
	rm -rf *.o led.bin led.elf led.dis

dump:
	arm-linux-gnueabihf-objdump -D led.elf > led.dis

dowmload:
	./imxdownload led.bin /dev/sdb

Final effect :

Probably 0.5s Time flashing .

Simple assembly delay code :

/**
 * Time delay 
*/
delay:
   ldr r2, =0xfffff
   ldr r3, =0x0
delay_loop:
   sub r2,r2, #1
   cmp r2,r3
   bne delay_loop
   mov pc,lr      @ Return the main function