ARM development (4) How to read the chip manual for novice Xiaobai, bare metal driver development steps and pure assembly to achieve lighting, assembly combined with c lighting, c to achieve lighting

一.How to read the chip manual（datasheet）

        as an embedded learner,How to read the chip manual is the top priority.No matter what the chip manual,How hype is written,Its essence is the instruction manual.

        可是问题来了,它YThis is the manual in English,But friends who are not good at English should not be too anxious,We now have good translation software,And as long as we read more and read more,Accumulate at a point in the future,Reading the chip manual is no longer a problem for you.

        Next, I will use a Samsung chip manual in a vivid image to lead you to read the chip manual together with how to carry out simple driver development,Learn how powerful it is.

二.Bare metal driver development steps

        1.When we get a board,If you want to achieve specific functions,The first thing we must think about is to understand what kind of function we want to achieve.（Here, I will take the lighting of lamps that students are annoying to see as an example）

        2.Now that we understand that our goal is to light up the lights,Then all we have to do next is find the little light bulb on the board（发光二极管）

        如图：

 然后我们看到了led【2-5】There are four small bulbs in total

        After finding the small light bulb and the name, we officially opened the road to lighting our lights.

Bare metal driver development

        （1）看电路图

                --1.Find the device I want to control（Take the small light bulb hereled2来举例）

                Open our peripheral hardware manual and search in the search barled2

                如图

                

         We know from this picture,这是一个npn三极管,The base is connectedcpuside control pinsCHG_COK,由cpuTo perform analog-to-digital conversion to control the high and low potentials,Determines the turn-on and turn-off of the transistor.Here we ignore the already marked onesGPX2_7.

        （2）看芯片手册

        搜索,The corresponding control module in the circuit diagram,然后如果有coreboardIf so, go there to find the corresponding oneGPX2-7.

        看模块的overviewLearn about the approximate functionality of this module.

        （3）Look at the control register

        What should we do if there are more registers？

        See sample programs provided by Technical Support,Find the register that needs to be modified（Often there are only a few）.

        Some manufacturers provide configuration software,Configure functions through the interface,We just need to use the value of the configured register.

Come to the chip manual,如图所示：

        

         （4）编程

        1.A macro that defines the register to be controlled（Corresponds to the register address in the manual）

        2.设备初始化（如设置GPIO的输出状态） tips：GPIO就是与cpu相连的引脚

        3.Break the functionality into the most basic pieces,逐个实现,如：点亮灯——灭灯——加延时——闪烁——跑马灯

        

The following code is in thiscpuand implemented on the development board：

cpu：samsung Exynos

开发板： FS4412

三.Pure assembly to achieve lighting

@ GPX2CON	寄存器地址： 0x11000000 + 0x0c40
	.text
	ldr r0, =0x11000c40		@ 将GPX2CONThe register address is moved to r0,那么r0 就代表 GPX2CON
	ldr r1, [r0]
	bic r1, #0xf0000000		@ 将 28~31The number bit is cleared
	orr r1, #0x10000000		@ 28The number bit is set1,The other bits remain unchanged,设置GPX2_7输出功能
	str r1, [r0]

	ldr r0, =0x114001e0		@ 将GPF3CONThe register address is moved to r0		GPF3_4
	ldr r1, [r0]			@ Get the contents of the address 4字节,相当于取出GPF3CON寄存器的内容
	bic r1, #0xf0000
	orr r1, #0x10000
	str r1, [r0]

while:
	ldr r2, =0x11000c44		@ 将GPX2DATThe address of the register is moved to r2
	ldr r3, [r2]
	orr r3, #0x80			@ 将GPX2DAT的7号位置 1,亮灯
	str r3, [r2]

	ldr r2, =0x114001e4		@ 将GPF3DAT
	ldr r3, [r2]
	orr r3, #0x10			@ 将GPF3DAT的4号位置 1,亮灯
	str r3, [r2]

	bl delay_1s

	ldr r2, =0x11000c44		@ 将GPX2DATThe address of the register is moved to r2
	ldr r3, [r2]
	bic r3, #0x80
	str r3, [r2]

	ldr r2, =0x114001e4		@ 将GPF3DAT
	ldr r3, [r2]
	bic r3, #0x10			@ 将GPF3DAT的4号位置 0,灭灯
	str r3, [r2]

	bl delay_1s

	b while
delay_1s:
	ldr r10, =0x4ffffff
loop:
	cmp r10, #0
	subgt r10, #1
	bgt loop
	mov pc, lr

	.end

makefile

CROSS=arm-linux-
CC=gcc
LD=ld
OC=objcopy

all: 
	$(CROSS)$(CC) -c start.s
	$(CROSS)$(LD) start.o -Ttext 40008000 -o start.elf
	$(CROSS)$(OC) -O binary -S start.elf start.bin

clean:
	rm *.o *.elf *.bin

四. assemblyc点灯

mian.c 实现延时

      > Created Time: 2022年08月10日 星期三 15时43分06秒
 ***********************************************************************/


void delay()
{
	int i, j;
	for(i = 0; i < 10000; i++)
		for(j = 0; j < 256; j++);
}


/*******************************end of file*****************************/

@ GPX2CON	寄存器地址： 0x11000000 + 0x0c40
	.text
	ldr r0, =0x11000c40		@ 将GPX2CONThe register address is moved to r0,那么r0 就代表 GPX2CON
	ldr r1, [r0]
	bic r1, #0xf0000000		@ 将 28~31The number bit is cleared
	orr r1, #0x10000000		@ 28The number bit is set1,The other bits remain unchanged,设置GPX2_7输出功能
	str r1, [r0]

	ldr r0, =0x114001e0		@ 将GPF3CONThe register address is moved to r0		GPF3_4
	ldr r1, [r0]			@ Get the contents of the address 4字节,相当于取出GPF3CON寄存器的内容
	bic r1, #0xf0000
	orr r1, #0x10000
	str r1, [r0]

while:
	ldr r2, =0x11000c44		@ 将GPX2DATThe address of the register is moved to r2
	ldr r3, [r2]
	orr r3, #0x80			@ 将GPX2DAT的7号位置 1,亮灯
	str r3, [r2]

	ldr r2, =0x114001e4		@ 将GPF3DAT
	ldr r3, [r2]
	orr r3, #0x10			@ 将GPF3DAT的4号位置 1,亮灯
	str r3, [r2]

	bl delay				@ 调用main.c中的delay函数,进行延时

	ldr r2, =0x11000c44		@ 将GPX2DATThe address of the register is moved to r2
	ldr r3, [r2]
	bic r3, #0x80
	str r3, [r2]

	ldr r2, =0x114001e4		@ 将GPF3DAT
	ldr r3, [r2]
	bic r3, #0x10			@ 将GPF3DAT的4号位置 0,灭灯
	str r3, [r2]

	bl delay				@ 调用main.c中的delay函数,进行延时

	b while


	.end

makefile

CROSS=arm-linux-
CC=gcc
LD=ld
OC=objcopy

all: 
	$(CROSS)$(CC) -c start.s
	$(CROSS)$(CC) -c main.c
	$(CROSS)$(LD) start.o main.o -Ttext 40008000 -o start.elf
	$(CROSS)$(OC) -O binary -S start.elf start.bin

clean:
	rm *.o *.elf *.bin

五.c实现点灯,This method is what we use the most,Also the easiest

 main.c

 ***********************************************************************/
void delay()
{
	int i, j;
	for(i = 0; i < 10000; i++)
		for(j = 0; j < 256; j++);
}

#define GPX2CON			*(volatile  unsigned int *)0x11000c40
#define GPX2DAT			*(volatile  unsigned int *)0x11000c44

void led2_init()
{
	// GPX2CON = GPX2CON & 0x0fffffff | (1 << 28)
	GPX2CON	= GPX2CON & (~(0xf << 28)) | ( 0x1 << 28 );
}
void led2_on()
{
	GPX2DAT = GPX2DAT | (1 << 7);
}
void led2_off()
{
	GPX2DAT = GPX2DAT & (~(1 << 7));
}
int main()
{
	led2_init();
	while(1){
		led2_on();
		delay();
		led2_off();
		delay();
	}
}

/*******************************end of file*****************************/

	.text

	b main

	.end

makefile

CROSS=arm-linux-
CC=gcc
LD=ld
OC=objcopy

all: 
	$(CROSS)$(CC) -c start.s
	$(CROSS)$(CC) -c main.c
	$(CROSS)$(LD) start.o main.o -Ttext 40008000 -o start.elf
	$(CROSS)$(OC) -O binary -S start.elf start.bin

clean:
	rm *.o *.elf *.bin

六.Pure assembly to achieve marquee

@ GPX2CON	寄存器地址： 0x11000000 + 0x0c40
	.text
	ldr r0, =0x11000c40		@ 将GPX2CONThe register address is moved to r0,那么r0 就代表 GPX2CON
	ldr r1, [r0]
	bic r1, #0xf0000000		@ 将 28~31The number bit is cleared
	orr r1, #0x10000000		@ 28The number bit is set1,The other bits remain unchanged,设置GPX2_7输出功能
	str r1, [r0]
    
    ldr r0,=0x11000c20
    ldr r1,[r0]
    bic r1,#0xf
    orr r1,#0x1
    str r1,[r0]

	ldr r0, =0x114001e0		@ 将GPF3CONThe register address is moved to r0		GPF3_4
	ldr r1, [r0]			@ Get the contents of the address 4字节,相当于取出GPF3CON寄存器的内容
	bic r1, #0xf0000
	orr r1, #0x10000
	str r1, [r0]

    ldr r0,=0x114001E0
    ldr r1,[r0]
    bic r1,#0xf00000
    orr r1,#0x100000
    str r1,[r0]

while:
@开灯led2
	ldr r2, =0x11000c44		@ 将GPX2DATThe address of the register is moved to r2
	ldr r3, [r2]
	orr r3, #0x80			@ 将GPX2DAT的7号位置 1,亮灯
	str r3, [r2]
	bl delay_1s
@开灯led3
    ldr r2,=0x11000c24
    ldr r3,[r2]
    orr r3,#0x1
    str r3,[r2]
	bl delay_1s


@开灯led4
	ldr r2, =0x114001e4		@ 将GPF3DAT
	ldr r3, [r2]
	orr r3, #0x10			@ 将GPF3DAT的4号位置 1,亮灯
	str r3, [r2]
	bl delay_1s
@开灯led5
    ldr r2,=0x114001E4
    ldr r3,[r2]
    orr r3,#0x20
    str r3,[r2]

	bl delay_1s
@关灯led2
	ldr r2, =0x11000c44		@ 将GPX2DATThe address of the register is moved to r2
	ldr r3, [r2]
	bic r3, #0x80
	str r3, [r2]
	bl delay_1s
@关灯led3
    ldr r2,=0x11000c24
    ldr r3,[r2]
    bic r3,#0x1
    str r3,[r2]
	bl delay_1s
@关灯led4
	ldr r2, =0x114001e4		@ 将GPF3DAT
	ldr r3, [r2]
	bic r3, #0x10			@ 将GPF3DAT的4号位置 0,灭灯
	str r3, [r2]
	bl delay_1s
@关灯led5
    ldr r2,=0x114001E4
    ldr r3,[r2]
    bic r3,#0x20
    str r3,[r2]

	bl delay_1s

	b while
delay_1s:
	ldr r10, =0x4ffffff
loop:
	cmp r10, #0
	subgt r10, #1
	bgt loop
	mov pc, lr

	.end

makefile

CROSS=arm-linux-
CC=gcc
LD=ld
OC=objcopy

all: 
	$(CROSS)$(CC) -c start.s
	$(CROSS)$(LD) start.o -Ttext 40008000 -o start.elf
	$(CROSS)$(OC) -O binary -S start.elf start.bin

clean:
	rm *.o *.elf *.bin