HPS_LED_HEX代码解读
刚刚学习SOC不久。这几天在DE1-SoC上编译和运行了友晶提供的一些sample，初步学习了一些相关代码，把自己的理解写下来，希望各位大侠不吝赐教。
1. 硬件（HPS-FPGA）架构在Qsys中连接h2f_lw_axi_master 到led_pio
把信号输出到10个FPGA 引脚：
soc_system_led_pio.v
always @(posedge clk or negedge reset_n)
begin
if (reset_n == 0)
data_out <= 1023;
else if (chipselect && ~write_n && (address == 0))
data_out <= writedata[9 : 0];
end
2. HPS侧软件打开内存设备
main.c
if(( fd = open( "/dev/mem", ( O_RDWR | O_SYNC ) ) ) == -1 ) {
printf("ERROR: could not open \"/dev/mem\"...\n" );
return(1 );
}
进行地址映射
virtual_base =mmap( NULL, HW_REGS_SPAN, ( PROT_READ | PROT_WRITE ), MAP_SHARED, fd,HW_REGS_BASE );
通过LWH2F bridge 映射到连接LED的PIO端口
h2p_lw_led_addr=virtual_base+ ((unsigned long)(ALT_LWFPGASLVS_OFST + LED_PIO_BASE ) & ( unsigned long)(HW_REGS_MASK ) );
其中LED_PIO_BASE 对应于Qsys中定义的地址
hps_0.h(87):#define LED_PIO_BASE 0x10040
创建点灯线程
ret=pthread_create(&id,NULL,(void*)led_blink,NULL);
点灯函数中调用LEDR_LightCount
void led_blink(void)
{
…
LEDR_LightCount(i);
}
LEDR_LightCount函数中调用alt_write_word
led.c
void LEDR_LightCount(unsigned char LightCount)
{ // 1: light, 0:unlight
…
alt_write_word(h2p_lw_led_addr, Mask ); //0:ligh, 1:unlight
}
alt_write_word实际上就是指针操作，把src地址的内容拷贝到dest
C:\altera\14.0\embedded\ip\altera\hps\altera_hps\hwlib\include\socal\socal.h
#define alt_write_word(dest, src) (*ALT_CAST(volatile uint32_t *, (dest))= (src))
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