实验：PIO外部中断
?轉自：http://www.cnblogs.com/chentuo/articles/1427402.html
?
實驗：PIO外部中斷
Author：Chen Tuo
Copyright ? Chen Tuo, 2008-2009. All rights reserved.
2008年3月1日創建
2009年3月26日修改
1.????? 實驗目的
熟悉NiosII PIO設備的訪問方法。學習邊沿觸發中斷。
2.????? 實驗設備
硬件：PC機，EP1C3或EP1C12核心板，MyEpx3實驗版。
軟件：Quartus II 7.2；MagaCore 7.2；Nios II IDE 7.2。
3.????? 實驗內容
用一個按鍵控制一個LED燈顯示。
4.????? 實驗預習要求
熟悉PIO外設的訪問和控制和PIO的中斷控制機制。
5.????? 實驗步驟
(1)??? 創建一個Quartus II項目PIOEINT。
(2)??? 如下圖，定制一個Nios II CPU，命名為myniosii。
?
其中：
l???????? onchip_mem為8K。啟動向量和異常向量配置如下：
?
l???????? KEY_PIO為1位輸入，如下圖設置為下降沿觸發中斷。
l???????? LED_PIO為1位輸出。
(3)??? 在Quartus II中創建一個原理圖，放置一個上面定制好的Nios II核myniosii，并如圖設置引腳。編譯、下載硬件配置到FPGA。
?
(4)??? 啟動Nios II IDE，新建一個空白Nios II C/C++ Application項目，并命名為pio_eint。
(5)??? 在pio_eint項目中添加一個C文件pio_eint.c。
(6)??? 設置pio_eint項目Properties屬性，對該項目的代碼編譯進行優化：
C/C++ Build > Tool Settings > General > Optimize size (-Os)
(7)??? 設置pio_eint_syslib項目Properties屬性，對該項目的代碼編譯進行優化：
a)?????? C/C++ Build > Tool Settings > General > Optimize size (-Os)
b)????? 在System library屬性頁面，清除Support C++和Clean exit (flush buffers)；選上Program、LightWeight device driver API、Reduced device drivers和Small C library。
(8)??? 編譯、調試、運行。
?????? 從上面的編譯、鏈接信息看到，優化后，pio_eint.elf文件代碼加指令總共只有1728字節，這樣實驗就完全可以在低成本的EP1C3系列芯片上進行。
6.????? 程序清單
PIO外部中斷實驗程序
/*************************************************************
?* 文件名：pio_eint.c
?* 功?能：用按鍵以中斷方式控制LED。每當有一次按鍵中斷時，取反LED一次
?* 說?明：按下KEY1觀察LED1的狀態
?************************************************************/
#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;???? //信號量：通知中斷事件發生
/*************************************************************
?* 名??? 稱：KeyDown_interrupts()
?* 功??? 能：鍵按下事件中斷服務子程序，當鍵按下時，通過down標志告知外界
?* 入口參數：context，一般用于傳遞中斷狀態寄存器的值，這里未使用
?*???????? id，中斷號，這里未使用
?* 出口參數：無
?************************************************************/
static void KeyDown_interrupts(void* context, alt_u32 id)
{
??? /* 清中斷捕獲寄存器 */
??? IOWR_ALTERA_AVALON_PIO_EDGE_CAP(PIO_KEY_BASE, ~KEYCON);
??? /* 通知外部有中斷事件發生 */
??? done++;
}
/*************************************************************
?* 名??? 稱：InitPIO()
?* 功??? 能：初始化PIO_KEY為輸入，PIO_LED為輸出，開中斷，清邊沿捕獲寄存器
?* 入口參數：無
?* 出口參數：無
?************************************************************/
void InitPIO(void)
{
??? /* 初始化PIO_KEY為輸入，PIO_LED為輸出 */??
??? IOWR_ALTERA_AVALON_PIO_DIRECTION(PIO_KEY_BASE, ~KEYCON); //0為輸入
??? IOWR_ALTERA_AVALON_PIO_DIRECTION(PIO_LED_BASE, LEDCON);?//1為輸出
??? /* 開PIO_KEY中斷 */
??? IOWR_ALTERA_AVALON_PIO_IRQ_MASK(PIO_KEY_BASE, KEYCON);
??? /* 清邊沿捕獲寄存器 */
??? IOWR_ALTERA_AVALON_PIO_EDGE_CAP(PIO_KEY_BASE, ~KEYCON);
??? /* 注冊中斷服務子程序 */
??? alt_irq_register(PIO_KEY_IRQ, NULL, KeyDown_interrupts);
}
/*************************************************************
?* 名??? 稱：main()
?* 功??? 能：等待按鍵中斷，并輸出控制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熄滅
??? InitPIO();
??? while(1)
??? {
??????? if(0 != done)
??????? {
??????????? done--;???????????????????? ???? //中斷事件數量減1
??????????? alt_busy_sleep(5000);?????? ?? //延時5ms
??????????? key_state = IORD_ALTERA_AVALON_PIO_DATA(PIO_KEY_BASE)&KEYCON;
??????????? if(key_state == 0xFF)?????? ?? //如果是由短暫脈沖引起的中斷，則忽略
??????????????? continue;?????????????? ??? //消除鍵盤抖動
??????????? new_state = ~(old_state^key_state); //按鍵按下時LED取反。
??????????? old_state = new_state;????? ?? //保存LED的狀態
??????????? IOWR_ALTERA_AVALON_PIO_DATA(PIO_LED_BASE, new_state);
??????? }
??? }
??? return(0);
}
?????? 注意：不要在中斷服務程序中進行等待或者其他阻塞性操作。
7.????? 中斷服務程序的調試
l???????? 在中斷服務程序內設置斷點。當中斷發生后，處理器會在斷點處停下，用戶可以單步調試中斷服務程序。
l???????? 使用spintf()函數把關鍵數據寫到內存中，然后觸發外部分析程序。在中斷服務程序中，不可調用printf()函數，因為它可能引起阻塞且運行時間無法預知，但可以調用sprintf()。
8.????? 鍵盤去抖動
?????? 由于按鍵的按下與抬起都會有10～20ms的抖動毛刺存在，如下圖所示。因此，為了獲取穩定的按鍵信息，須要避開這段抖動期。
?????? 去抖動的方法有很多種，如使用R-S觸發器的硬件方法、運用不同算法的各種軟件方法等。硬件方法會增加成本和體積，對于按鍵較多的矩陣式鍵盤，一般會使用硬件方法；一般情況下軟件方法用的比較普遍，但加固定延時的去抖動法效率最低，它以無謂地耗費機時來實現去抖動。本例采用短延時加異或算法消除鍵盤抖動。
9.????? system.h
?????? system.h文件在路徑"PIOEINT"software"pio_eint_syslib"Debug"system_description下。注意：system.h要編譯以后才有。system.h頭文件是根據SOPC Builder生成的myniosii.ptf文件產生的系統硬件信息的宏定義文件，清單如下：
/* 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位于路徑C:"altera"72"ip"sopc_builder_ip"altera_avalon_pio"inc下。該頭文件提供PIO內核寄存器訪問宏定義，程序中對I/O端口操作的宏定義都在該文件中。其清單如下：
#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__ */
?????? 下面是與中斷屏蔽寄存器相關的宏定義說明。
中斷屏蔽寄存器訪問宏定義
| 宏定義 | 意義 |
| IOADDR_ALTERA_AVALON_PIO_IRQ_MASK(base) | 計算中斷屏蔽寄存器的物理地址。參數base為PIO內核的基地址 |
| IORD_ALTERA_AVALON_PIO_IRQ_MASK(base) | 讀取中斷屏蔽寄存器的內容 |
| IOWR_ALTERA_AVALON_PIO_IRQ_MASK(base, data) | 寫中斷屏蔽寄存器。參數data為向中斷屏蔽寄存器寫入的數據 |
11.alt_types.h
?????? alt_types.h位于路徑C:"altera"72"nios2eds"components"altera_nios2"HAL"inc下。它定義與altera Nios II自己的與編譯器無關的數據類型。其清單如下：
#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位于路徑C:"altera"72"nios2eds"components"altera_nios2"HAL"inc"sys下。它定義了與中斷相關的函數（參見定時器實驗），如alt_irq_register()。其清單如下：
#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位于路徑C:"altera"72"nios2eds"components"altera_nios2"HAL"inc"priv下。它定義了延時函數alt_busy_sleep。其清單如下：
#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 */
14.參考文獻
[1] 周立功，等. SOPC嵌入式系統實驗教程(一)[M]. 北京:北京航空航天大學出版社,2006.
[2] 李蘭英，等. Nios II 嵌入式軟核 SOPC設計原理及應用[M]. 北京:北京航空航天大學出版社,2006.
[3] http://www.altera.com.cn/.
[4] http://www.icembed.com/info-16530.htm 一種軟件去除鍵抖動的方法.
?
轉載于:https://www.cnblogs.com/xinjie/archive/2009/07/31/1536174.html
總結
以上是生活随笔為你收集整理的实验：PIO外部中断的全部內容，希望文章能夠幫你解決所遇到的問題。
- 上一篇： 舵机工作原理及程序[通俗易懂]
- 下一篇： ACCESS 文本文件导入和导出指定字段