Re: [Discuss-gnuradio] What to do after binary slicer?

[Paul Boven]

Hi Guilherme,

On 08/14/2018 05:45 PM, Guilherme Theis wrote:
> I made this FSK flow and I noticed that my outpout is getting zero 
> padded, which means that if I have a bit 1 my output comes as "00000001" 
> and if I have a bit 0 my output come as "00000000", I suppose that this 
> is something related to the binary slicer. How can I delete those extra 
> zeros? I thought I could do that with one of those blocks:
>
> 1) Binary repack;
> 2) Packed to unpacked
> 3) Unpacked to packed
>
> I made some test with those blocks, but I can't understand how they 
> work, even if they present a "expected" output. 

The outcome of the slicer will always be a zero or one, and each sample 
is sent as a byte, either 0x00 or 0x01 as you already discovered.

To store them more efficiently, you would use either the 'Unpacked to 
Packed', the 'Pack K bits' blocks or the 'Repack Bits' blocks.

If you use 'Pack K bits' and set K to 8, it neatly packs every 8 bytes 
(with only a 0 or 1 in them) into a single byte. The first bit to arrive 
will get weight 128, then 64, then 32 etc, and the last bit will have a 
weight of 1. The data rate out of that block is therefore only 1/8th of 
its input data rate.

You can use that block between your slicer and file source in the flowchart.

Regards, Paul Boven.