软件：Quatus II 6.1,Nios II 6.1

硬件：EP1C3T144 FPGA开发板

实验目的:熟悉nios II开发,掌握中断程序调试

系统配置：CPU+OnChipRam(4K)+LED_PIO+BUTTON_PIO

功能描述：按键实现中断，使led亮或灭

led配置成开发板上的led0,led1,led2,led3

按键采用简单按钮B17,B18,19,B20

不给过多注释了(其实注释够多了)

#include

#include

#include "sys/alt_irq.h"

#include "altera_avalon_pio_regs.h"

#include "system.h"

/* A variable to hold the value of the button pio edge capture register. */

volatile int edge_capture;

#ifdef BUTTON_PIO_BASE

/* 按键中断服务程序*/

static void handle_button_interrupts(void* context, alt_u32 id)

{

/* Cast context to edge_capture's type. It is important that this be

* declared volatile to avoid unwanted compiler optimization.

*/

volatile int* edge_capture_ptr = (volatile int*) context;

/* Store the value in the Button's edge capture register in *context. */

*edge_capture_ptr = IORD_ALTERA_AVALON_PIO_EDGE_CAP(BUTTON_PIO_BASE);

/* Reset the Button's edge capture register. */

IOWR_ALTERA_AVALON_PIO_EDGE_CAP(BUTTON_PIO_BASE, 0);

}

/* Initialize the button_pio. */

static void init_button_pio()

{

/* Recast the edge_capture pointer to match the alt_irq_register() function

* prototype. */

void* edge_capture_ptr = (void*) &edge_capture;

/* Enable all 4 button interrupts. */

IOWR_ALTERA_AVALON_PIO_IRQ_MASK(BUTTON_PIO_BASE, 0xf);

/* Reset the edge capture register. */

IOWR_ALTERA_AVALON_PIO_EDGE_CAP(BUTTON_PIO_BASE, 0x0);

/* Register the interrupt handler. */

alt_irq_register( BUTTON_PIO_IRQ, edge_capture_ptr,

handle_button_interrupts );

}

#endif

int main (void) __attribute__ ((weak, alias ("alt_main")));

int alt_main(void)

{

alt_irq_init(ALT_IRQ_BASE); //necessary,enable interrupts

alt_sys_init();//unnecessary

alt_io_redirect(ALT_STDOUT,ALT_STDIN,ALT_STDERR);//unnecessary

init_button_pio();

while(1)

{

switch(edge_capture)

{

case 0x01:

IOWR_ALTERA_AVALON_PIO_DATA(LED_PIO_BASE,0xFF);

break;

case 0x02:

IOWR_ALTERA_AVALON_PIO_DATA(LED_PIO_BASE,0x00);

break;

case 0x04:

IOWR_ALTERA_AVALON_PIO_DATA(LED_PIO_BASE,0xFF);

break;

case 0x08:

IOWR_ALTERA_AVALON_PIO_DATA(LED_PIO_BASE,0x00);

break;

default:

IOWR_ALTERA_AVALON_PIO_DATA(LED_PIO_BASE,0x0A);

break;

}

}

return 0;

}

1 因为使用的是片上RAM,容量有限,故得重载alt_main(), 否则空间不够

2 系统默认的alt_main()是干了很多活的...比如系统中断,IO设备驱动等,改写的时候得注意,哪些用户程序用到了.比如本例用到中断,故 alt_irq_init(ALT_IRQ_BASE);函数是必须的.开始没有调试成功就是因为没有开总中断

中断的调试过程可以依次看以下:

status:最低位PIE（使能），为０禁止，为１允许中断

ienable:32３２位，每位对应一个外部中断，为１则对应使能

ipending:表示处理器正在处理的中断

全局变量：alt_irq.若注册成功的话就会向向量表写入ＩＳＲ和Context.注册完后返回０则成功，为负则失败