TX2440 bare metal program - LED

1. GPIO Description

GPIO (General Purpose I/O ports) is a general purpose input/output port. In practical applications, whether it is connecting an LCD, connecting a keyboard, controlling a running light, etc., it is inseparable from the operation of I/O. It can be said that GPIO operation is the basis of all hardware operations.

S3C2440 has 130 I/O ports, divided into nine groups: GPA, GPB, ..., GPJ. We can operate these IOs through registers. S3C2440 has three registers: GPxCON, GPxDAT, and GPxUP. GPxCON is used to select pin functions; GPxDAT is used to read/write pin data; GPxUp is used to determine whether to use internal pull-up resistors. It should be noted that Group A does not have a GPAUP register, that is, Group A I/O ports do not have a pull-up resistor selection function

1、GPxCON

The GPxCON of the A group I/O port is special. Each bit in GPACON corresponds to a pin (a total of 23 pins). When a bit is set to 0, the corresponding pin is an output pin. Otherwise, the corresponding pin is an address line or used for address control. In this case, GPADAT is useless.

The I/O of Group B to Group J are identical in register operation. Every two bits in GPxCON control one pin: 00 indicates input, 01 indicates output, 10 indicates special function, and 11 is reserved.

2、GPxDAT

GPxDAT is used to read/write pin data: when the pin is set to output, writing the corresponding bit of its register can make the pin output high or low level; when the pin is set to input, reading the corresponding bit of this register can determine whether the level state of the pin is high or low.

3、GPxUP

GPxUP is used to set whether the corresponding pin uses a pull-up resistor. When a bit is 0, a pull-up resistor is used; when a bit is 1, a pull-up resistor is not used.

2. Development Environment

IDE environment: ADS1.2

Development board: TX2440

Hardware wiring diagram:

LED1---GPF0, common anode connection, to light up the LED, just give the corresponding low level.

LED2---GPF1

LED3---GPF2

LED4---GPF3

3. Source code and analysis

//======================================================================

// Project name: LED.mcp

// Function description: Use GPIO to control four LEDs

// IDE environment: ADS v1.2

// Component file: main.c

//======================================================================

//====================================================

// Include header file area

//====================================================

#include "2440addr.h"

#include "2440lib.h"

#include "option.h"

#include "def.h"

#include "uart.h"

#define LED1ON 0xFE //LED1 lighting value is 0xFE (low level lighting)

#define LED2ON (LED1ON<<1) //LED2 lighting value is LED1 shifted left by 1 bit

#define LED3ON (LED1ON<<2) //LED3 light value is LED2 shifted left by 1 bit

#define LED4ON (LED1ON<<3) //LED4 lighting value is LED3 shifted left by 1 bit

extern unsigned int PCLK;

void usDelay(unsigned long time)

{

U32 i,j;

for (i = time; i > 0; i--)

for (j = 50; j > 0; j--);

}

void Main(void)

{

   rGPFCON = (rGPFCON | 0xFFFF) & 0xFFFFFF55; //GPF0--GPF3 are set to output       

   rGPFUP  =  0xFFFF;

   rGPFDAT = 0x0F; //GPF lower 4 bits are initialized to 1

   while(1)

    {

    rGPFDAT = LED1ON; //Turn on LED1

        usDelay(10000);

        rGPFDAT = LED2ON; //Turn on LED2

         usDelay(10000);

        rGPFDAT = LED3ON; //Turn on LED3

        usDelay(10000);

         rGPFDAT = LED4ON; //Turn on LED4   

         usDelay(10000);       

    }

}

Test result: LED1--4 light up in sequence, all go out, and then light up in sequence.