2018年10月11日 | OK6410裸机学习之串口实验

start.S文件：

.globl _start

_start:

// 硬件相关的设置 

    // Peri port setup 

    ldr r0, =0x70000000

    orr r0, r0, #0x13

    mcr p15,0,r0,c15,c2,4       @ 256M(0x70000000-0x7fffffff)

// 关看门狗 

    // 往WTCON(0x7E004000)写0 

    ldr r0, =0x7E004000

    mov r1, #0

    str r1, [r0]

    // 设置栈 

    ldr sp, =8*1024

    // 设置时钟 

    bl clock_init

    bl main

halt:

    b halt    

=====================================================================

clock.c源码：

#define APLL_LOCK (*((volatile unsigned long *)0x7E00F000))

#define MPLL_LOCK (*((volatile unsigned long *)0x7E00F004))

#define EPLL_LOCK (*((volatile unsigned long *)0x7E00F008))

#define OTHERS    (*((volatile unsigned long *)0x7e00f900))

#define CLK_DIV0  (*((volatile unsigned long *)0x7E00F020))

#define ARM_RATIO    0   // ARMCLK = DOUTAPLL / (ARM_RATIO + 1)    

#define HCLKX2_RATIO 4   // HCLKX2 = HCLKX2IN / (HCLKX2_RATIO + 1) = 100MHz 

#define HCLK_RATIO   0   // HCLK = HCLKX2 / (HCLK_RATIO + 1)   = 100MHz       

#define PCLK_RATIO   1   // PCLK   = HCLKX2 / (PCLK_RATIO + 1) = 50MHz    

#define MPLL_RATIO   0   // DOUTMPLL = MOUTMPLL / (MPLL_RATIO + 1)     

#define APLL_CON  (*((volatile unsigned long *)0x7E00F00C))

#define APLL_CON_VAL  ((1<<31) | (250 << 16) | (3 << 8) | (1))  

#define MPLL_CON  (*((volatile unsigned long *)0x7E00F010))

#define MPLL_CON_VAL  ((1<<31) | (250 << 16) | (3 << 8) | (1))

#define CLK_SRC  (*((volatile unsigned long *)0x7E00F01C))

//MDIV=250 对应： ARMCLK = 500MHz, HCLK = 100MHz, PCLK = 50MHZ 

//MDIV=266 对应： ARMCLK = 532MHz, HCLK = 133MHz, PCLK = 66.5MHZ 

void clock_init(void)

{

    APLL_LOCK = 0xffff;

    MPLL_LOCK = 0xffff;

    EPLL_LOCK = 0xffff;

    // set async mode 当CPU时钟 != HCLK时，要设为异步模式 

    OTHERS &= ~0xc0;

    while ((OTHERS & 0xf00) != 0);

    CLK_DIV0 = (ARM_RATIO) | (MPLL_RATIO << 4) | (HCLK_RATIO << 8) | (HCLKX2_RATIO << 9) | (PCLK_RATIO << 12);

    APLL_CON = APLL_CON_VAL;    // 500MHz 

    MPLL_CON = MPLL_CON_VAL;  // 500MHz 

    CLK_SRC = 0x03;

}

====================================================================

uart.c源码：

#define ULCON0     (*((volatile unsigned long *)0x7F005000))

#define UCON0      (*((volatile unsigned long *)0x7F005004))

#define UFCON0     (*((volatile unsigned long *)0x7F005008))

#define UMCON0     (*((volatile unsigned long *)0x7F00500C))

#define UTRSTAT0   (*((volatile unsigned long *)0x7F005010))

#define UFSTAT0    (*((volatile unsigned long *)0x7F005018))

#define UTXH0      (*((volatile unsigned char *)0x7F005020))

#define URXH0      (*((volatile unsigned char *)0x7F005024))

#define UBRDIV0    (*((volatile unsigned short *)0x7F005028))

#define UDIVSLOT0  (*((volatile unsigned short *)0x7F00502C))

#define GPACON     (*((volatile unsigned long *)0x7F008000))

void init_uart(void)

{

    GPACON &= ~0xff;

    GPACON |= 0x22;

    // ULCON0 

    ULCON0 = 0x3;  // 数据位:8, 无较验, 停止位: 1, 8n1 

    UCON0  = 0x5;  // 使能UART发送、接收 

    UFCON0 = 0x01; // FIFO ENABLE 

    UMCON0 = 0;

    // 波特率 

    // DIV_VAL = (PCLK / (bps x 16 ) ) - 1 

    // bps = 57600

    // DIV_VAL = (66500000 / (115200 x 16 ) ) - 1 

    //         = 35.08

    UBRDIV0   = 35;

    // x/16 = 0.08

    // x = 1

    UDIVSLOT0 = 0x1;

}

char getchar(void)

{

    while ((UFSTAT0 & 0x7f) == 0);                           //判断接收缓存区是否为空

    return URXH0;

}

void putchar(char c)

{

    while (UFSTAT0 & (1<<14));                                //判断发送缓存区是否已满

    UTXH0 = c;

}

=====================================================================

main.c源码：

#include "uart.h"

int main()

{

    char c;

    init_uart();

    while (1)

    {

        c = getchar();

        putchar(c+1);

    }

    return 0;

}

=====================================================================

Makefile：

uart.bin: start.o main.o uart.o clock.o

    arm-linux-ld -Ttext 0 -o uart.elf $^

    arm-linux-objcopy -O binary uart.elf uart.bin

    arm-linux-objdump -D uart.elf > uart.dis

%.o : %.S

    arm-linux-gcc -o $@ $< -c

%.o : %.c

    arm-linux-gcc -o $@ $< -c -fno-builtin-putc   //-fno-builtin-putc避免putc函数名冲突

clean:

    rm *.o uart.elf uart.bin uart.dis