"Embedded Linux+arm" Gpio operation

1.GPIO Introduction

GPIO (General purpose I/O ports) means universal input/output port, which is popularly said to be some pins.

We can use them to output high or low levels or the state of the read-in PIN.

There are 130 I/O ports in the s3c2440, divided into 9 groups A~j, GPA, GPB 、..... GPJ

2.GPIO Registers

Since the gpio is to be manipulated, the corresponding registers must be operated, and the GPIO registers in 2440 are:

gpxcon--Select Pin function (input, output, retention, etc.)

gpxdat--used to read and write pins

gpcup--One is 1 o'clock, the corresponding pin has no internal pull-up resistor; for 0 o'clock, there is an internal pull-up resistor

3. Schematic diagram

Led:

Keys:

4. Experiment Code: >> using assembly language to achieve illumination:

led_on. S

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2. . text
4. . Global _start
6. _start:
8. LDR R0, =0x56000050 //gpfcon Register Address
10. MOV R1, #0x00001500 //See technical Manual corresponding configuration, general 01 for the output pin
12. STR R1, [R0] //set to output
16. LDR R0, =0x56000054 //gpfdat Register
18. MOV R1, #0x00000000
20. STR R1, [R0] //gpfdat Register write value
22. Main_loop:
24. B main_loop //Cycle wait

Makefile:

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1. led_on.bin:led_on. S
2. Arm-linux-gcc-g-C led_on. S-o LED_ON.O
3. Arm-linux-ld-ttext 0x00000000-g led_on.o-o led_on_elf //-ttext to set the connection address
4. Arm-linux-objcopy-o binary-s led_on_elf led_on.bin //convert elf files to. bin Files
5. Clean
6. RM-RF *.bin *.O *elf

>> Lighting with C language

Use C to write, need a boot file, can be used to close the door, set the stack and so on.

Crt0. S

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2. . text
4. . Global _begin
6. _begin:
8. LDR R0, =0x53000000 //watchdog register address
10. MOV R1, #0x00000000 //write 0 forbidden watchdog
12. STR R1, [R0]
16. LDR SP, =1024*4 //Set stack, note cannot be greater than 4 K, because now the available SRAM space is only 4 K
18. BL main //Call the main function, and finally note that the assembly language case does not matter
20. _loop:
22. B _loop

Led_on_c.c

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1. #define GPFCON * (volatile unsigned long *) 0x56000050
2. #define GPFDAT * (volatile unsigned long *) 0x56000054
4. int main ()
5. {
6. gpfcon=0x00001500; //Simple configuration for Output
7. gpfdat=0x00000000; ///Simple output 0, the above schematic shows that the corresponding LED will illuminate
9. return 0;
10. }

Makefile

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2. Led_on_c.bin:crt0. S LED_ON_C.C
4. Arm-linux-gcc-g-c-o crt0.o crt0. S
6. Arm-linux-gcc-g-c-o LED_ON_C.O LED_ON_C.C
8. Arm-linux-ld-ttext 0x0000000-g crt0.o Led_on_c.o-o led_on_c_elf
10. Arm-linux-objcopy-o binary-s led_on_c_elf Led_on_c.bin
12. arm-linux-objdump-d-M arm led_on_c_elf > Led_on_c.dis //convert elf files to disassembly files
14. Clean
16. Rm-f Led_on_c.dis led_on_c.bin led_on_c_elf *.o

>> use key +c language for lighting

Look at the schematic diagram above, the principle is that the PIN PIN is configured as input pin, to read the status of the pin;

When the key is pressed, the pin reads low, and when the key is released, it is read to a high level;

Crt0. s ibid;

Key_led.c

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2. /*
4. GPF4 GPF5 GPF6--led
8. GPF0 GPF2 GPG3--key
10. */
14. #define GPFCON (* (volatile unsigned long *) 0x56000050)
16. #define GPFDAT (* (volatile unsigned long *) 0x56000054)
20. #define GPGCON (* (volatile unsigned long *) 0x56000060)
22. #define GPGDAT (* (volatile unsigned long *) 0x56000064)
26. #define Gpf4_out (1<< (4*2))
28. #define Gpf5_out (1<< (5*2))
30. #define Gpf6_out (1<< (6*2))
34. #define GPF4_MSK (3<< (4*2))
36. #define GPF5_MSK (3<< (5*2))
38. #define GPF6_MSK (3<< (6*2))
42. #define GPF0_IN (0<< (0*2))
44. #define GPF2_IN (0<< (2*2))
46. #define GPG3_IN (0<< (3*2))
50. #define GPF0_MSK (3<< (0*2))
52. #define GPF2_MSK (3<< (2*2))
54. #define GPG3_MSK (3<< (3*2))
58. int main ()
60. {
62. unsigned long dwdat;
64. //1 Output Pin
66. Gpfcon &= ~ (Gpf4_msk | Gpf5_msk | GPF6_MSK);
68. Gpfcon |= (Gpf4_out | Gpf5_out | Gpf6_out);
72. //input Pin
74. Gpfcon &= ~ (Gpf0_msk | GPF2_MSK);
76. Gpfcon |= (gpf0_in | GPF2_IN);
78. Gpgcon &= ~gpg3_msk;
80. Gpgcon |= gpg3_in;
84. While (1)
86. {
88. Dwdat = Gpfdat;
90. if (Dwdat & (1<<0))
92. Gpfdat |= (1<<4);
94. Else
96. Gpfdat &= ~ (1<<4); //light
100. if (Dwdat & (1<<2))
102. Gpfdat |= (1<<5);
104. Else
106. Gpfdat &= ~ (1<<5);
110. Dwdat = Gpgdat;
112. if (Dwdat & (1<<3))
114. Gpfdat |= (1<<6);
116. Else
118. Gpfdat &= ~ (1<<6);
120. }
124. return 0;
126. }

Makefile the corresponding modification can be;

The above program compiles will get bin file, we burn it into NAND flash, can use tools, can also be cured in NOR flash uboot to burn, many methods, after burning, power on, 2440CPU will automatically put NAND Flash 4k content, copied to 2440 in 4k SRAM run, this memory commonly known as stepping stone area.

Note: Original article, reproduced please specify the source: http://blog.csdn.net/scottly1/article/details/38960309

"Embedded Linux+arm" Gpio operation