2018年10月12日 | Tiny210裸机PWM控制蜂鸣器

start.S源码：

.global _start

_start:

    ldr sp, =0xD0030000  // 初始化栈，因为后面要调用C函数 

    bl clock_init                // 初始化时钟 

    bl ddr_init                   // 初始化内存 

    bl nand_init                // 初始化NAND 

    ldr r0, =0x36000000  // 要拷贝到DDR中的位置 

    ldr r1, =0x0                // 从NAND的0地址开始拷贝 

    ldr r2, =bss_start       // BSS段的开始地址 

    sub r2,r2,r0                // 要拷贝的大小 

    bl nand_read            // 拷贝数据 

clean_bss:

    ldr r0, =bss_start

    ldr r1, =bss_end

    mov r3, #0

    cmp r0, r1

    ldreq pc, =on_ddr

clean_loop:

    str r3, [r0], #4

    cmp r0, r1    

    bne clean_loop        

    ldr pc, =on_ddr

on_ddr:

    ldr sp, =0x3f000000    // 重新初始化栈，指向内存 

    ldr pc, =main

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

timer.c源码：

#define    GPD0CON     (*(volatile unsigned int *)0xE02000A0) 

#define    TCFG0           (*(volatile unsigned int *)0xE2500000) 

#define    TCFG1           (*(volatile unsigned int *)0xE2500004) 

#define    TCON            (*(volatile unsigned int *)0xE2500008) 

#define    TCNTB0         (*(volatile unsigned int *)0xE250000C) 

#define    TCMPB0        (*(volatile unsigned int *)0xE2500010) 

#define    TCNTO0        (*(volatile unsigned int *)0xE2500014) 

void pwm_init(void)

{

    // 配置为GPD0_0用于PWM输出 

    GPD0CON |= (0x2 << 0);     // TOUT_0 

}

void timer0_init(void)

{

    // 设置时钟源

    // Timer0 input clock Frequency = 66700000 / ( {prescaler + 1} ) / {divider value} 

    //      = 66700000 / (1+1) / 1

    //      = 33350000( 即1s计数33350000次 )

    TCFG0 &= ~(0xff);

    TCFG0  |= 1;        // Prescaler = 1 

    TCFG1  &= ~0xf;     // 0000 = 1/1 

    // 设置TCNTB0(即PWM的频率) 

    TCNTB0 = 33350;     // PWM的频率为1KHz  

    // 设置TCMPB0(即PWM的占空比) 

    TCMPB0 = 16675;     // 占空比为50% 

    TCON &= ~(1<<2);    // 不进行电平反转(即引脚初始值为0) 

    TCON |= (1<<3);     // auto-reload 

}

void pwm_start(void)

{

    TCON |= (1<<1);   // set manual update 

    TCON |= (1<<0);   // start timer 0 

    TCON &= ~(1<<1);  // clean manual update 

}

void pwm_stop(void)

{

    TCON &= ~(1<<0);   // stop timer 0 

}

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

command.c源码：

#include "lib.h"

#include "nand.h"

#include "timer.h"

int help(int argc, char * argv[])

{

    wy_printf("do_command 《%s》 \n", argv[0]);      //"《"实际为"<"

    wy_printf("help message: \n");

    wy_printf("md - memory dispaly\n");

    wy_printf("mw - memory write\n");

    wy_printf("nand read - nand read sdram_addr nand_addr size\n");

    wy_printf("nand write - nand write sdram_addr nand_addr size\n");

    wy_printf("pwm on - turn on buzzer \n");

    wy_printf("pwm off - turn off buzzer\n");

    return 0;

}

int md(int argc, char * argv[])

{    

    unsigned long *p = (unsigned long *)0;

    int i, j;

    wy_printf("do_command 《%s》 \n", argv[0]);

    if (argc <= 1) {

        wy_printf ("Usage:\n%s\n", "md address");

        return 1;

    }

    if (argc >= 2)

        p = (unsigned long *)atoi(argv[1]);

    for (j = 0; j < 16; j++)

    {    

        wy_printf("%x: ", p);

        for (i = 0; i < 4; i++)

            wy_printf("%x ", *p++);    

        wy_printf("\n");

    }

    return 0;

}

int mw(int argc, char * argv[])

{    

    unsigned long *p = (unsigned long *)0;

    int v = 0;

    wy_printf("do_command 《%s》 \n", argv[0]);//"《"实际为"<"

    if (argc <= 2) {

        wy_printf ("Usage:\n%s\n", "md address data");

        return 1;

    }

    if (argc >= 2)

        p = (unsigned long *)atoi(argv[1]);

    if (argc >= 3)

        v = atoi(argv[2]);

    *p = v;

    return 0;

}

int nand(int argc, char *argv[])

{

    int nand_addr, sdram_addr;

    unsigned int size;

    if (argc < 5)

    {

        wy_printf("nand read sdram_addr nand_addr size\n");

        wy_printf("nand write sdram_addr nand_addr size\n");

        return 0;

    }

    sdram_addr = atoi(argv[2]);

    nand_addr = atoi(argv[3]);

    size = atoi(argv[4]);

    wy_printf("do_command 《%s》 \n", argv[0]);

    wy_printf("sdram 0x%x, nand 0x%x, size 0x%x\n", sdram_addr, nand_addr, size);

    if (strcmp(argv[1], "read") == 0)

        nand_read((unsigned char *)sdram_addr, nand_addr, size);

    if (strcmp(argv[1], "write") == 0)

        nand_write(sdram_addr, nand_addr, size);    

    wy_printf("nand %s finished!\n", argv[1]);

    return 0;

}

int pwm(int argc, char *argv[])

{

    pwm_init();

    if (argc < 2)

    {

        wy_printf("pwm on - turn on buzzer \n");

        wy_printf("pwm off - turn on buzzer\n");

        return 0;

    }

    if (strcmp(argv[1], "on") == 0)

        pwm_start();

    if (strcmp(argv[1], "off") == 0)

        pwm_stop();

    return 0;

}

void run_command(int argc, char * argv[])

{

    if (strcmp(argv[0], "help") == 0)

    {

        help(argc, argv);

        return;

    }

    if (strcmp(argv[0], "md") == 0)

    {

        md(argc, argv);

        return;

    }

    if (strcmp(argv[0], "mw") == 0)

    {

        mw(argc, argv);

        return;

    }

    if (strcmp(argv[0], "pwm") == 0)

    {

        pwm(argc, argv);

        return;

    }

    if (strcmp(argv[0], "nand") == 0)

        nand(argc, argv);

    if(argc >= 1)

        wy_printf("Unknown command '%s' - try 'help' \n",argv[0]);

    return;

}

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

main.c源码：

#include "command.h"

#include "clock.h"

#include "led.h"

#include "uart.h"

#include "lib.h"

#include "nand.h"

#define   CFG_PROMPT  "WY_BOOT # " // Monitor Command Prompt    

#define   CFG_CBSIZE  256                      // Console I/O Buffer Size    

char *argv[10];

int readline (const char *const prompt)

{

    char console_buffer[CFG_CBSIZE];      // console I/O buffer    

    char *buf = console_buffer;

    int argc = 0;

    int state = 0;

    //puts(prompt);

    wy_printf("%s",prompt);

    gets(console_buffer);

    while (*buf)

    {

        if (*buf != ' ' && state == 0)

        {

            argv[argc++] = buf;

            state = 1;

        }

        if (*buf == ' ' && state == 1)

        {

            *buf = '\0';

            state = 0;

        }

        buf++;    

    }

    return argc;

}

void message(void)

{

    wy_printf("\nThis bootloader support some command to test peripheral:\n");

    wy_printf("Such as: LCD, IIS, BUZZER \n");

    wy_printf("Try 'help' to learn them \n\n");    

}

int main(void)

{

    char buf[6];

    int argc = 0;

    int i = 0;

    led_init();    // 设置对应管脚为输出 

    uart_init();   // 初始化UART0 

    nand_read_id(buf);

    timer0_init(); // 初始化定时器0，用于PWM输出，延时1S 

    wy_printf("\n**********************************************************\n");

    wy_printf("                     wy_bootloader\n");

    wy_printf("                     vars: %d \n",2012);

    wy_printf("                     nand id:");

    putchar_hex(buf[0]);

    putchar_hex(buf[1]);

    putchar_hex(buf[2]);

    putchar_hex(buf[3]);

    putchar_hex(buf[4]);

    wy_printf("\n**********************************************************\n");

    while (1)

    {

        argc = readline (CFG_PROMPT);

        if(argc == 0 && i ==0)

        {

            message();

            i=1;

        }

        run_command(argc, argv);

    }

    return 0;

}

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

Makefile文件：

uart.bin:start.s main.c uart.c clock.c led.c lib.c command.c nand.c mem_setup.S timer.c

    arm-linux-gcc -nostdlib -c start.s -o start.o

    arm-linux-gcc -nostdlib -c main.c -o main.o

    arm-linux-gcc -nostdlib -c uart.c -o uart.o

    arm-linux-gcc -nostdlib -c lib.c -o lib.o

    arm-linux-gcc -nostdlib -c clock.c -o clock.o    

    arm-linux-gcc -nostdlib -c led.c -o led.o    

    arm-linux-gcc -nostdlib -c command.c -o command.o    

    arm-linux-gcc -nostdlib -c nand.c -o nand.o    

    arm-linux-gcc -nostdlib -c timer.c -o timer.o    

    arm-linux-gcc -nostdlib -c mem_setup.S -o mem_setup.o    

    arm-linux-ld -T bootloader.lds start.o main.o uart.o lib.o clock.o led.o command.o nand.o mem_setup.o timer.o -o uart_elf

    arm-linux-objcopy -O binary -S uart_elf uart.bin

clean:

    rm -rf *.o *.bin uart_elf *.dis

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

bootloader.lds链接文件：

SECTIONS {

    . = 0x36000010;

    .text : {

        * (.text)

    }

    . = ALIGN(4);

    .rodata : {

        * (.rodata)

    }

    . = ALIGN(4);

    .data : {

        * (.data)

    }

    . = ALIGN(4);

    bss_start = .;

    .bss  : { *(.bss)  *(COMMON) }

    bss_end = .;

}

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

一，定时器用于PWM输出(驱动蜂鸣器)：

下面，先介绍下定时器的几个关键的寄存器吧：

问：大家都知道，定时器的实现，其实就是一个计数的过程(从0家到一个数字或从一个数字减到0)，那么这个数字从哪里来呢？

答：从寄存器TCNTBx中获得，当我们编程时，写入一个数组到该寄存器，然后通过手动装载或自动装载，就会把该寄存器的值用于"一个数字"了。

问：PWM波形是高低电平交替出现的，那么定时器输出的电平什么时候翻转呢？

答：这个情况和TCMPBx寄存器中的值有关系，当计数器中的值("一个数字")减到(或加到)和TCMPBx寄存器中的值相等时，电平翻转。

本来想多说点的，但是实在是没什么可说的，直接上部分代码吧：

void timer0_init(void)

{

    // 设置时钟源

    // Timer0 input clock Frequency = 66700000 / ( {prescaler + 1} ) / {divider value} 

    //      = 66700000 / (1+1) / 1

    //      = 33350000( 即1s计数33350000次 )

    TCFG0 &= ~(0xff);

    TCFG0  |= 1;            // Prescaler = 1 

    TCFG1  &= ~0xf;     // 0000 = 1/1 

    // 设置TCNTB0(即PWM的频率) 

    TCNTB0 = 33350;   // PWM的频率为1KHz   

    // 设置TCMPB0(即PWM的占空比) 

    TCMPB0 = 16675;  // 占空比为50% 

    TCON &= ~(1<<2); // 不进行电平反转(即引脚初始值为0) 

    TCON |= (1<<3);     // auto-reload 

}

以上是定时器的初始化代码，关于定时器用于PWM输出的代码我以经共享在了"Tiny210学习日记_代码"目录下了，名为"14_pwm"。请大家自己阅读，十分简单。

测试方法：(在终端输入命令)

pwm on           (蜂鸣器响)

pwm off           (蜂鸣器不响)