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How to read a nibble?

 
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eguti



Joined: 01 Jan 2012
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How to read a nibble?
PostPosted: Fri Jan 06, 2012 12:16 am     Reply with quote

The code "value = input_x()" could read an entire Byte from 8 pins. But, how to read just 4 pins in the same way of the input_x() command?

I think is easy with input(PIN_X) command, but is there another way?

thank
n-squared



Joined: 03 Oct 2006
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PostPosted: Fri Jan 06, 2012 12:25 am     Reply with quote

There is no way of reading a nibble DIRECTLY.
What you can do is input_x() and AND it with a mask:
Code:

  X = input_b() & 0x0F; / bits 0 to 3
  Y = input_b() >> 4; // bits 4 to 7
  Z = (input_b() & 0x3C) >> 2; // bits 2 to 5


BR
NN
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Ttelmah



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PostPosted: Fri Jan 06, 2012 2:56 am     Reply with quote

As an extra comment, look at the 'swap' function in CCS. This uses a single byte command to swap the high and low nibbles in a byte. Much more efficient than four rotations.

Best Wishes
eguti



Joined: 01 Jan 2012
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PostPosted: Fri Jan 06, 2012 8:01 am     Reply with quote

Thanks Ttelmah and n-squared. I will try both tips.

bye
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