小程序有几条语句不太懂。

cat12620 · 发表于 2019-9-2 13:45

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本帖最后由 cat12620 于 2019-9-2 15:29 编辑

#include <stdio.h>
#include <unistd.h>
#include <fcntl.h>
#include <sys/mman.h>
#include "hwlib.h"
#include "socal/socal.h"
#include "socal/hps.h"
#include "socal/alt_gpio.h"
#include "hps_0.h"

#define HW_REGS_BASE ( ALT_STM_OFST )
#define HW_REGS_SPAN ( 0x04000000 )
#define HW_REGS_MASK ( HW_REGS_SPAN - 1 )

int main() {

      void *virtual_base;
      int fd;
      int loop_count;
      int led_direction;
      int led_mask;
      void *h2p_lw_led_addr;

      // map the address space for the LED registers into user space so we can interact with them.
      // we'll actually map in the entire CSR span of the HPS since we want to access various registers within that span

      if( ( fd = open( "/dev/mem", ( O_RDWR | O_SYNC ) ) ) == -1 ) {
            printf( "ERROR: could not open \"/dev/mem\"...\n" );
            return( 1 );
      }

      virtual_base = mmap( NULL, HW_REGS_SPAN, ( PROT_READ | PROT_WRITE ), MAP_SHARED, fd, HW_REGS_BASE );

      if( virtual_base == MAP_FAILED ) {
            printf( "ERROR: mmap() failed...\n" );
            close( fd );
            return( 1 );
      }

      h2p_lw_led_addr=virtual_base + ( ( unsigned long  )( ALT_LWFPGASLVS_OFST + PIO_LED_BASE ) & ( unsigned long)( HW_REGS_MASK ) );


      // toggle the LEDs a bit

      loop_count = 0;
      led_mask = 0x01;
      led_direction = 0; // 0: left to right direction
      while( loop_count < 60 ) {

            // control led,  add ~ because the led is low-active
            *(uint32_t *)h2p_lw_led_addr = ~led_mask;

            // wait 100ms
            usleep( 100*1000 );

            // update led mask
            if (led_direction == 0){
                     led_mask <<= 1;
                     if (led_mask == (0x01 << (PIO_LED_DATA_WIDTH-1)))
                              led_direction = 1;
            }else{
                     led_mask >>= 1;
                     if (led_mask == 0x01){
                              led_direction = 0;
                              loop_count++;
                     }
            }

      } // while


      // clean up our memory mapping and exit

      if( munmap( virtual_base, HW_REGS_SPAN ) != 0 ) {
            printf( "ERROR: munmap() failed...\n" );
            close( fd );
            return( 1 );
      }

      close( fd );

      return( 0 );
}
首先说h2p_lw_led_addr=virtual_base + ( ( unsigned long  )( ALT_LWFPGASLVS_OFST + PIO_LED_BASE ) & ( unsigned long)( HW_REGS_MASK ) );，ALT_LWFPGASLVS_OFST 是什么？

我发现他的值是0xff200000，在<hps.h>头文件里。在qsys工程里面有一个Pio_led的元件，他相对于lwaxi的偏移地址被宏定义为PIO_LED_BASE，其值为0x0，( unsigned long  )( ALT_LWFPGASLVS_OFST + PIO_LED_BASE，这两个加起来是什么意思，为什么要加起来？

然后为什么又与 HW_REGS_MASK进行一个与?最开始的几个宏定义的值代表着什么意思？在其中一个宏定义里面有用到ALT_STM_OFST，这个是什么？

上面几个问题请教大神，非常感谢！

xixihahaheihei · 发表于 2019-9-2 21:15

还以为是分享的代码

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小程序有几条语句不太懂。

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