BIT order LSB to MSB and vice versa

[Dirk Bubley]

Hello together,

i try to find my way with BIT manipulation inside a byte.

One problem i can`t solve is changing the bit order inside a byte.

Example i would like to change the order from LSB------MSB to MSB------LSB or vice versa.

Any help would be aprechiated.

BR

Dirk

[medelec35]

Hi Dirk,
Not sure if this is a helpful for you or not,
but here are could be couple of solutions?

1st Is from a V5 flowchart.
Since you have not got V5 here is a screen shot:

Binary swap.png

(15.82 KiB) Downloaded 1755 times

You could also go to:
http://www.matrixmultimedia.com/mmforum ... 891#p32952
Where you will find a post by Spanish_dude

Martin

[JonnyW]

The link Martin posts to will work great if you are streaming your data (highest bit first).

If you want to invert a byte and store the new value you can do this in 1 calculation icon:

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  byte = (byte >> 7) | (byte >> 5) | (byte >> 3) | (byte >> 1) | (byte << 1) | (byte << 3) | (byte << 5) | (byte << 7)

This is then the inverted byte. You could put this call in a macro for ease of use (argument is byte, return is inverted byte). If you upgrade to v5, then you can use this macro call direct (for neatness) in decision icons, calculations, etc:

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  byte = invert(byte)

I hope this is useful.

Jonny

[Dirk Bubley]

Hi Jonny,

your bit shift idea is looking good to me. Is this working in simulation too.

Because i feed the LCD Display with the new modified byte and i get strange results.


BR Dirk

[JonnyW]

Ah, sorry! That's what I get for posting after my bedtime. That will not work at all, forget that code.

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byte = (byte >> 7) & 1 | (byte >> 5) & 2 | (byte >> 3) & 4 | (byte >> 1) & 8 | (byte << 1) & 0x10 | (byte << 3) & 0x20 | (byte << 5) & 0x40| (byte << 7) & 0x80

The code I posted would have 'smeared' the bits across the byte, instead of shifting them on their own. The '&' will isolate each bit correctly.

Jonny

[Dirk Bubley]

Hi Jonny,

perfect it is working that solved my problem!! Many thanks!!

BR

Dirk