转自：http://www.cnblogs.com/chentuo/articles/1427402.html

实验：PIO外部中断

Author：Chen Tuo

Copyright © Chen Tuo, 2008-2009. All rights reserved.

2008年3月1日创建

2009年3月26日修改

1. 实验目的

熟悉NiosII PIO设备的访问方法。学习边沿触发中断。

2. 实验设备

硬件：PC机，EP1C3或EP1C12核心板，MyEpx3实验版。

软件：Quartus II 7.2；MagaCore 7.2；Nios II IDE 7.2。

3. 实验内容

用一个按键控制一个LED灯显示。

4. 实验预习要求

熟悉PIO外设的访问和控制和PIO的中断控制机制。

5. 实验步骤

(1) 创建一个Quartus II项目PIOEINT。

(2) 如下图，定制一个Nios II CPU，命名为myniosii。

其中：

l onchip_mem为8K。启动向量和异常向量配置如下：

l KEY_PIO为1位输入，如下图设置为下降沿触发中断。

l LED_PIO为1位输出。

(3) 在Quartus II中创建一个原理图，放置一个上面定制好的Nios II核myniosii，并如图设置引脚。编译、下载硬件配置到FPGA。

(4) 启动Nios II IDE，新建一个空白Nios II C/C++ Application项目，并命名为pio_eint。

(5) 在pio_eint项目中添加一个C文件pio_eint.c。

(6) 设置pio_eint项目Properties属性，对该项目的代码编译进行优化：

C/C++ Build > Tool Settings > General > Optimize size (-Os)

(7) 设置pio_eint_syslib项目Properties属性，对该项目的代码编译进行优化：

a) C/C++ Build > Tool Settings > General > Optimize size (-Os)

b) 在System library属性页面，清除Support C++和Clean exit (flush buffers)；选上Program、LightWeight device driver API、Reduced device drivers和Small C library。

(8) 编译、调试、运行。

从上面的编译、链接信息看到，优化后，pio_eint.elf文件代码加指令总共只有1728字节，这样实验就完全可以在低成本的EP1C3系列芯片上进行。

6. 程序清单

PIO外部中断实验程序

/*************************************************************

* 文件名：pio_eint.c

* 功能：用按键以中断方式控制LED。每当有一次按键中断时，取反LED一次

* 说明：按下KEY1观察LED1的状态

************************************************************/

#include <stdio.h>

#include "system.h"

#include "altera_avalon_pio_regs.h"

#include "alt_types.h"

#include "sys/alt_irq.h"

#include "priv/alt_busy_sleep.h"

#define LEDCON 0x01

#define KEYCON 0x01

volatile alt_u32 done = 0;     //信号量：通知中断事件发生

/*************************************************************

* 名 称：KeyDown_interrupts()

* 功 能：键按下事件中断服务子程序，当键按下时，通过down标志告知外界

* 入口参数：context，一般用于传递中断状态寄存器的值，这里未使用

*         id，中断号，这里未使用

* 出口参数：无

************************************************************/

static void KeyDown_interrupts(void* context, alt_u32 id)

{

/* 清中断捕获寄存器 */

IOWR_ALTERA_AVALON_PIO_EDGE_CAP(PIO_KEY_BASE, ~KEYCON);

/* 通知外部有中断事件发生 */

done++;

}

/*************************************************************

* 名 称：InitPIO()

* 功 能：初始化PIO_KEY为输入，PIO_LED为输出，开中断，清边沿捕获寄存器

* 入口参数：无

* 出口参数：无

************************************************************/

void InitPIO(void)

{

/* 初始化PIO_KEY为输入，PIO_LED为输出 */

IOWR_ALTERA_AVALON_PIO_DIRECTION(PIO_KEY_BASE, ~KEYCON); //0为输入

IOWR_ALTERA_AVALON_PIO_DIRECTION(PIO_LED_BASE, LEDCON); //1为输出

/* 开PIO_KEY中断 */

IOWR_ALTERA_AVALON_PIO_IRQ_MASK(PIO_KEY_BASE, KEYCON);

/* 清边沿捕获寄存器 */

IOWR_ALTERA_AVALON_PIO_EDGE_CAP(PIO_KEY_BASE, ~KEYCON);

/* 注册中断服务子程序 */

alt_irq_register(PIO_KEY_IRQ, NULL, KeyDown_interrupts);

}

/*************************************************************

* 名 称：main()

* 功 能：等待按键中断，并输出控制LED

************************************************************/

int main(void)

{

volatile alt_u32 key_state, old_state, new_state;

old_state = KEYCON;

IOWR_ALTERA_AVALON_PIO_DATA(PIO_LED_BASE, old_state); //初始化LED熄灭

InitPIO();

while(1)

{

if(0 != done)

{

done--;                          //中断事件数量减1

alt_busy_sleep(5000);          //延时5ms

key_state = IORD_ALTERA_AVALON_PIO_DATA(PIO_KEY_BASE)&KEYCON;

if(key_state == 0xFF)          //如果是由短暂脉冲引起的中断，则忽略

continue;                   //消除键盘抖动

new_state = ~(old_state^key_state); //按键按下时LED取反。

old_state = new_state;         //保存LED的状态

IOWR_ALTERA_AVALON_PIO_DATA(PIO_LED_BASE, new_state);

}

}

return(0);

}

注意：不要在中断服务程序中进行等待或者其他阻塞性操作。

7. 中断服务程序的调试

l 在中断服务程序内设置断点。当中断发生后，处理器会在断点处停下，用户可以单步调试中断服务程序。

l 使用spintf()函数把关键数据写到内存中，然后触发外部分析程序。在中断服务程序中，不可调用printf()函数，因为它可能引起阻塞且运行时间无法预知，但可以调用sprintf()。

8. 键盘去抖动

由于按键的按下与抬起都会有10～20ms的抖动毛刺存在，如下图所示。因此，为了获取稳定的按键信息，须要避开这段抖动期。

去抖动的方法有很多种，如使用R-S触发器的硬件方法、运用不同算法的各种软件方法等。硬件方法会增加成本和体积，对于按键较多的矩阵式键盘，一般会使用硬件方法；一般情况下软件方法用的比较普遍，但加固定延时的去抖动法效率最低，它以无谓地耗费机时来实现去抖动。本例采用短延时加异或算法消除键盘抖动。

9. system.h

system.h文件在路径"PIOEINT"software"pio_eint_syslib"Debug"system_description下。注意：system.h要编译以后才有。system.h头文件是根据SOPC Builder生成的myniosii.ptf文件产生的系统硬件信息的宏定义文件，清单如下：

/* system.h

*

* Machine generated for a CPU named "cpu" as defined in:

* d:"lecture"embed"FPGA"SOPCExample1C12"PIO"PIOEINT"software"pio_eint_syslib"..".."myniosii.ptf

*

* Generated: 2009-03-31 07:55:41.873

*

*/

#ifndef __SYSTEM_H_

#define __SYSTEM_H_

/*

* system configuration

*

*/

#define ALT_SYSTEM_NAME "myniosii"

#define ALT_CPU_NAME "cpu"

#define ALT_CPU_ARCHITECTURE "altera_nios2"

#define ALT_DEVICE_FAMILY "CYCLONE"

#define ALT_STDIN "/dev/null"

#define ALT_STDIN_TYPE ""

#define ALT_STDIN_BASE UNDEFINED VARIABLE %BASE_ADDRESS%

#define ALT_STDIN_DEV null

#define ALT_STDOUT "/dev/null"

#define ALT_STDOUT_TYPE ""

#define ALT_STDOUT_BASE UNDEFINED VARIABLE %BASE_ADDRESS%

#define ALT_STDOUT_DEV null

#define ALT_STDERR "/dev/null"

#define ALT_STDERR_TYPE ""

#define ALT_STDERR_BASE UNDEFINED VARIABLE %BASE_ADDRESS%

#define ALT_STDERR_DEV null

#define ALT_CPU_FREQ 50000000

#define ALT_IRQ_BASE NULL

/*

* processor configuration

*

*/

#define NIOS2_CPU_IMPLEMENTATION "tiny"

#define NIOS2_BIG_ENDIAN 0

#define NIOS2_ICACHE_SIZE 0

#define NIOS2_DCACHE_SIZE 0

#define NIOS2_ICACHE_LINE_SIZE 0

#define NIOS2_ICACHE_LINE_SIZE_LOG2 0

#define NIOS2_DCACHE_LINE_SIZE 0

#define NIOS2_DCACHE_LINE_SIZE_LOG2 0

#define NIOS2_FLUSHDA_SUPPORTED

#define NIOS2_EXCEPTION_ADDR 0x00002020

#define NIOS2_RESET_ADDR 0x00002000

#define NIOS2_BREAK_ADDR 0x00004820

#define NIOS2_HAS_DEBUG_STUB

#define NIOS2_CPU_ID_SIZE 1

#define NIOS2_CPU_ID_VALUE 0

/*

* A define for each class of peripheral

*

*/

#define __ALTERA_AVALON_ONCHIP_MEMORY2

#define __ALTERA_AVALON_PIO

/*

* onchip_mem configuration

*

*/

#define ONCHIP_MEM_NAME "/dev/onchip_mem"

#define ONCHIP_MEM_TYPE "altera_avalon_onchip_memory2"

#define ONCHIP_MEM_BASE 0x00002000

#define ONCHIP_MEM_SPAN 8192

#define ONCHIP_MEM_ALLOW_MRAM_SIM_CONTENTS_ONLY_FILE 0

#define ONCHIP_MEM_RAM_BLOCK_TYPE "M4K"

#define ONCHIP_MEM_INIT_CONTENTS_FILE "onchip_mem"

#define ONCHIP_MEM_NON_DEFAULT_INIT_FILE_ENABLED 0

#define ONCHIP_MEM_GUI_RAM_BLOCK_TYPE "Automatic"

#define ONCHIP_MEM_WRITEABLE 1

#define ONCHIP_MEM_DUAL_PORT 0

#define ONCHIP_MEM_SIZE_VALUE 8192

#define ONCHIP_MEM_SIZE_MULTIPLE 1

#define ONCHIP_MEM_USE_SHALLOW_MEM_BLOCKS 0

#define ONCHIP_MEM_INIT_MEM_CONTENT 1

#define ONCHIP_MEM_ALLOW_IN_SYSTEM_MEMORY_CONTENT_EDITOR 0

#define ONCHIP_MEM_INSTANCE_ID "NONE"

#define ONCHIP_MEM_IGNORE_AUTO_BLOCK_TYPE_ASSIGNMENT 1

#define ONCHIP_MEM_CONTENTS_INFO "QUARTUS_PROJECT_DIR/onchip_mem.hex 1238111903"

#define ALT_MODULE_CLASS_onchip_mem altera_avalon_onchip_memory2

/*

* pio_key configuration

*

*/

#define PIO_KEY_NAME "/dev/pio_key"

#define PIO_KEY_TYPE "altera_avalon_pio"

#define PIO_KEY_BASE 0x00005000

#define PIO_KEY_SPAN 16

#define PIO_KEY_IRQ 0

#define PIO_KEY_DO_TEST_BENCH_WIRING 0

#define PIO_KEY_DRIVEN_SIM_VALUE 0

#define PIO_KEY_HAS_TRI 0

#define PIO_KEY_HAS_OUT 0

#define PIO_KEY_HAS_IN 1

#define PIO_KEY_CAPTURE 1

#define PIO_KEY_DATA_WIDTH 1

#define PIO_KEY_EDGE_TYPE "RISING"

#define PIO_KEY_IRQ_TYPE "EDGE"

#define PIO_KEY_BIT_CLEARING_EDGE_REGISTER 0

#define PIO_KEY_FREQ 50000000

#define ALT_MODULE_CLASS_pio_key altera_avalon_pio

/*

* pio_led configuration

*

*/

#define PIO_LED_NAME "/dev/pio_led"

#define PIO_LED_TYPE "altera_avalon_pio"

#define PIO_LED_BASE 0x00005010

#define PIO_LED_SPAN 16

#define PIO_LED_DO_TEST_BENCH_WIRING 0

#define PIO_LED_DRIVEN_SIM_VALUE 0

#define PIO_LED_HAS_TRI 0

#define PIO_LED_HAS_OUT 1

#define PIO_LED_HAS_IN 0

#define PIO_LED_CAPTURE 0

#define PIO_LED_DATA_WIDTH 1

#define PIO_LED_EDGE_TYPE "NONE"

#define PIO_LED_IRQ_TYPE "NONE"

#define PIO_LED_BIT_CLEARING_EDGE_REGISTER 0

#define PIO_LED_FREQ 50000000

#define ALT_MODULE_CLASS_pio_led altera_avalon_pio

/*

* system library configuration

*

*/

#define ALT_MAX_FD 32

#define ALT_SYS_CLK none

#define ALT_TIMESTAMP_CLK none

/*

* Devices associated with code sections.

*

*/

#define ALT_TEXT_DEVICE       ONCHIP_MEM

#define ALT_RODATA_DEVICE     ONCHIP_MEM

#define ALT_RWDATA_DEVICE     ONCHIP_MEM

#define ALT_EXCEPTIONS_DEVICE ONCHIP_MEM

#define ALT_RESET_DEVICE      ONCHIP_MEM

/*

* The text section is initialised so no bootloader will be required.

* Set a variable to tell crt0.S to provide code at the reset address and

* to initialise rwdata if appropriate.

*/

#define ALT_NO_BOOTLOADER

#endif /* __SYSTEM_H_ */

10.altera_avalon_pio_regs.h

altera_avalon_pio_regs.h位于路径C:"altera"72"ip"sopc_builder_ip"altera_avalon_pio"inc下。该头文件提供PIO内核寄存器访问宏定义，程序中对I/O端口操作的宏定义都在该文件中。其清单如下：

#ifndef __ALTERA_AVALON_PIO_REGS_H__

#define __ALTERA_AVALON_PIO_REGS_H__

#include <io.h>

#define IOADDR_ALTERA_AVALON_PIO_DATA(base)           __IO_CALC_ADDRESS_NATIVE(base, 0)

#define IORD_ALTERA_AVALON_PIO_DATA(base)             IORD(base, 0)

#define IOWR_ALTERA_AVALON_PIO_DATA(base, data)       IOWR(base, 0, data)

#define IOADDR_ALTERA_AVALON_PIO_DIRECTION(base)      __IO_CALC_ADDRESS_NATIVE(base, 1)

#define IORD_ALTERA_AVALON_PIO_DIRECTION(base)        IORD(base, 1)

#define IOWR_ALTERA_AVALON_PIO_DIRECTION(base, data) IOWR(base, 1, data)

#define IOADDR_ALTERA_AVALON_PIO_IRQ_MASK(base)       __IO_CALC_ADDRESS_NATIVE(base, 2)

#define IORD_ALTERA_AVALON_PIO_IRQ_MASK(base)         IORD(base, 2)

#define IOWR_ALTERA_AVALON_PIO_IRQ_MASK(base, data)   IOWR(base, 2, data)

#define IOADDR_ALTERA_AVALON_PIO_EDGE_CAP(base)       __IO_CALC_ADDRESS_NATIVE(base, 3)

#define IORD_ALTERA_AVALON_PIO_EDGE_CAP(base)         IORD(base, 3)

#define IOWR_ALTERA_AVALON_PIO_EDGE_CAP(base, data)   IOWR(base, 3, data)

/* Defintions for direction-register operation with bi-directional PIOs */

#define ALTERA_AVALON_PIO_DIRECTION_INPUT 0

#define ALTERA_AVALON_PIO_DIRECTION_OUTPUT 1

#endif /* __ALTERA_AVALON_PIO_REGS_H__ */

下面是与中断屏蔽寄存器相关的宏定义说明。

中断屏蔽寄存器访问宏定义

宏定义	意义
IOADDR_ALTERA_AVALON_PIO_IRQ_MASK(base)	计算中断屏蔽寄存器的物理地址。参数base为PIO内核的基地址
IORD_ALTERA_AVALON_PIO_IRQ_MASK(base)	读取中断屏蔽寄存器的内容
IOWR_ALTERA_AVALON_PIO_IRQ_MASK(base, data)	写中断屏蔽寄存器。参数data为向中断屏蔽寄存器写入的数据

11.alt_types.h

alt_types.h位于路径C:"altera"72"nios2eds"components"altera_nios2"HAL"inc下。它定义与altera Nios II自己的与编译器无关的数据类型。其清单如下：

#ifndef __ALT_TYPES_H__

#define __ALT_TYPES_H__

/*

* Don't declare these typedefs if this file is included by assembly source.

*/

#ifndef ALT_ASM_SRC

typedef signed char alt_8;

typedef unsigned char alt_u8;

typedef signed short alt_16;

typedef unsigned short alt_u16;

typedef signed long alt_32;

typedef unsigned long alt_u32;

typedef long long alt_64;

typedef unsigned long long alt_u64;

#endif

#define ALT_INLINE        __inline__

#define ALT_ALWAYS_INLINE __attribute__ ((always_inline))

#define ALT_WEAK          __attribute__((weak))

#endif /* __ALT_TYPES_H__ */

12.sys/alt_irq.h

sys/alt_irq.h位于路径C:"altera"72"nios2eds"components"altera_nios2"HAL"inc"sys下。它定义了与中断相关的函数（参见定时器实验），如alt_irq_register()。其清单如下：

#endif /* __ALT_TYPES_H__ */

#ifndef __ALT_IRQ_H__

#define __ALT_IRQ_H__

/*

* alt_irq.h is the nios2 specific implementation of the interrupt controller

* interface.

*/

#include <errno.h>

#include "nios2.h"

#include "alt_types.h"

#ifdef __cplusplus

extern "C"

{

#endif /* __cplusplus */

/*

* Macros used by alt_irq_enabled

*/

#define ALT_IRQ_ENABLED 1

#define ALT_IRQ_DISABLED 0

/*

* number of available interrupts

*/

#define ALT_NIRQ NIOS2_NIRQ

/*

* Used by alt_irq_disable_all() and alt_irq_enable_all().

*/

typedef int alt_irq_context;

/*

* alt_irq_enabled can be called to determine if interrupts are enabled. The

* return value is zero if interrupts are disabled, and non-zero otherwise.

*/

static ALT_INLINE int ALT_ALWAYS_INLINE alt_irq_enabled (void)

{

int status;

NIOS2_READ_STATUS (status);

return status & NIOS2_STATUS_PIE_MSK;

}

/*

* alt_irq_init() is the device initialisation function. This is called at

* config time, before any other driver is initialised.

*/

static ALT_INLINE void ALT_ALWAYS_INLINE

alt_irq_init (const void* base)

{

NIOS2_WRITE_IENABLE (0);

NIOS2_WRITE_STATUS (NIOS2_STATUS_PIE_MSK);

}

/*

* alt_irq_register() can be used to register an interrupt handler. If the

* function is succesful, then the requested interrupt will be enabled upon

* return.

*/

extern int alt_irq_register (alt_u32 id,

void*   context,

void (*irq_handler)(void*, alt_u32));

/*

* alt_irq_disable_all() inhibits all interrupts.

*/

static ALT_INLINE alt_irq_context ALT_ALWAYS_INLINE

alt_irq_disable_all (void)

{

alt_irq_context context;

NIOS2_READ_STATUS (context);

NIOS2_WRITE_STATUS (0);

return context;

}

/*

* alt_irq_enable_all() re-enable all interrupts that currently have registered

* interrupt handlers (and which have not been masked by a call to

* alt_irq_disable()).

*/

static ALT_INLINE void ALT_ALWAYS_INLINE

alt_irq_enable_all (alt_irq_context context)

{

NIOS2_WRITE_STATUS (context);

}

/*

* alt_irq_disable() disables the individual interrupt indicated by "id".

*/

static ALT_INLINE int ALT_ALWAYS_INLINE alt_irq_disable (alt_u32 id)

{

alt_irq_context status;

extern volatile alt_u32 alt_irq_active;

status = alt_irq_disable_all ();

alt_irq_active &= ~(1 << id);

NIOS2_WRITE_IENABLE (alt_irq_active);

alt_irq_enable_all(status);

return 0;

}

/*

* alt_irq_enable() enables the individual interrupt indicated by "id".

*

*/

static ALT_INLINE int ALT_ALWAYS_INLINE alt_irq_enable (alt_u32 id)

{

alt_irq_context status;

extern volatile alt_u32 alt_irq_active;

status = alt_irq_disable_all ();

alt_irq_active |= (1 << id);

NIOS2_WRITE_IENABLE (alt_irq_active);

alt_irq_enable_all(status);

return 0;

}

#ifndef ALT_EXCEPTION_STACK

/*

* alt_irq_initerruptable() should only be called from within an ISR. It is used

* to allow higer priority interrupts to interrupt the current ISR. The input

* argument, "priority", is the priority, i.e. interrupt number of the current

* interrupt.

*

* If this function is called, then the ISR is required to make a call to

* alt_irq_non_interruptible() before returning. The input argument to

* alt_irq_non_interruptible() is the return value from alt_irq_interruptible().

*

* Care should be taken when using this pair of functions, since they increasing

* the system overhead associated with interrupt handling.

*

* If you are using an exception stack then nested interrupts won't work, so

* these functions are not available in that case.

*/

static ALT_INLINE alt_u32 ALT_ALWAYS_INLINE alt_irq_interruptible (alt_u32 priority)

{

extern volatile alt_u32 alt_priority_mask;

extern volatile alt_u32 alt_irq_active;

alt_u32 old_priority;

old_priority      = alt_priority_mask;

alt_priority_mask = (1 << priority) - 1;

NIOS2_WRITE_IENABLE (alt_irq_active & alt_priority_mask);

NIOS2_WRITE_STATUS (1);

return old_priority;

}

/*

* See Comments above for alt_irq_interruptible() for an explanation of the use of this

* function.

*/

static ALT_INLINE void ALT_ALWAYS_INLINE alt_irq_non_interruptible (alt_u32 mask)

{

extern volatile alt_u32 alt_priority_mask;

extern volatile alt_u32 alt_irq_active;

NIOS2_WRITE_STATUS (0);

alt_priority_mask = mask;

NIOS2_WRITE_IENABLE (mask & alt_irq_active);

}

#endif

/*

* alt_irq_pending() returns a bit list of the current pending interrupts.

* This is used by alt_irq_handler() to determine which registered interrupt

* handlers should be called.

*/

static ALT_INLINE alt_u32 ALT_ALWAYS_INLINE alt_irq_pending (void)

{

alt_u32 active;

NIOS2_READ_IPENDING (active);

return active;

}

#ifdef __cplusplus

}

#endif /* __cplusplus */

#endif /* __ALT_IRQ_H__ */

13.priv/alt_busy_sleep.h

priv/alt_busy_sleep.h位于路径C:"altera"72"nios2eds"components"altera_nios2"HAL"inc"priv下。它定义了延时函数alt_busy_sleep。其清单如下：

#ifndef __ALT_BUSY_SLEEP_H

#define __ALT_BUSY_SLEEP_H

/*

* The function alt_busy_sleep provides a busy loop implementation of usleep.

* This is used to provide usleep for the standalone HAL, or when the timer is

* unavailable in uC/OS-II.

*/

extern unsigned int alt_busy_sleep (unsigned int us);

#endif /* __ALT_BUSY_SLEEP_H */

14.参考文献

[1] 周立功，等. SOPC嵌入式系统实验教程(一)[M]. 北京:北京航空航天大学出版社,2006.

[2] 李兰英，等. Nios II 嵌入式软核 SOPC设计原理及应用[M]. 北京:北京航空航天大学出版社,2006.

[3] http://www.altera.com.cn/.

[4] http://www.icembed.com/info-16530.htm 一种软件去除键抖动的方法.