Guys, please help me, I've been stuck for 3 days and can't figure it out

51...

Guys, please help me, I've been stuck for 3 days and can't figure it out [Copy link]

Why is it that in Figure 2, the light matrix can be lit up using the sub-function format, but in Figure 1 the format only lights up for a moment and never lights up again?

51...

annysky2012

You copied the code into the post, the photo is not clear

PiThta

Sorry, I don't see what the problem is. If you solve it, please give me a kick.

damiaa

hang =hang<<1;

Changes the contents of the hang[] array.

To:

dat=hang[b]; //后面内容同右边试下。

for(i=0;i<8;i++)

{

  ....

}

A function that takes a variable as a parameter will not change the contents of the parameter. The contents of the parameter can only be changed if it takes a pointer or array as a parameter.

That dat=hang ; can't be changed, so I changed it below:

damiaa

dat=hang[b];

wangerxian

The above answer is correct. In Figure 1, the [hang] array has been modified, and in Figure 2, an intermediate variable dat is used, and the [hang] array has not been modified.

huo_hu

My understanding is that it is optimized. The compiler thinks that hang[b]=hang[b]<<1; is unnecessary to execute. You can check the assembly code to verify it.

In addition, for (i = 0; i < 8... and then look up 8421 in the table is a bit cumbersome, so it is smoother to change it to for (i = 1; i! = 0; i <<= 1)

PiThta

Absolutely, after reading the above, I realized the original poster's question:

Can only be output once.

At this point, the problem is indeed as described above. I always thought that this operation could output data, which is quite different from what the poster asked.

After the first output, each byte of data is shifted right by 8 bits. Generally speaking, right or left shifts (unsigned numbers) are filled with 0. That is to say, after the first output, the host's data has all become 0, which is why there is no output.

PiThta

You can use the second method to write in the future and pass the value into a temporary variable.

or

unsigned char temp=0x80;

for(i = 0; i < 8; i++) {

temp=0x80;

if(TRUE == hang[i] & temp) {

/* Corresponding operation*/

} else {

/* Corresponding operation*/

}

temp >>= 1;

/* Similarly, perform bit judgment from high to low */

}