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Original question:

Compiler/CC1350: FEC decoder at receiver side of CC1350

Compiler/CC1350: How payload enters the Convolutional Encoder- lsb first or msb first ?

Ryan Maroun
Intellectual 920 points
Part Number: CC1350

Tool/software: TI C/C++ Compiler

Hi guys, 

Im trying to understand how payload enters the Convolutional Encoder if first msb of payload enters or lsb of payload enters the Convolutional Encoder?

for example, lets assume in smartRF studio the payload in mode 2 is : 1f1f so it's in binary [0 0 0 1 1 1 1 1 0 0 0 1 1 1 1 1] , so payload in binary is: [0 0 0 1 1 1 1 1 0 0 0 1 1 1 1 1]  .

how this pattern (payload) enters the Convolutional Encoder? lsb (right most bit of the pattern - 1) first or msb(left most bit first- 0 )?

I mean by lsb first what's enter to the encoder => 0 then 0 then 0 then 1 then 1 then 1 then 1 then 1 then 0 ...etc

I mean by msb first what's enter to the encoder =>  1 then 1 then 1 then 1 then 1 then 0 then 0 then 0  ...etc

so how the payload data enters the encoder?

attaching down a graph from swr64 of encoding scheme of cc1350. the data bits in the left side is implicitly my payload binary data.

thanks alot for any assistance !

  • 0
    TI__Guru**** 317180 points

    Based on https://www.ti.com/lit/an/swra642/swra642.pdf, LSB first. 

    Is this for a University project? 

  • 0 in reply to TER
    Intellectual 920 points

    Thanks alot !

    for your question yes.

    Another question about DSSS block, the input top it enters as LSB first as encoder right?

    for instance for DSSS = 4  (according to swr64 the patterns are 0 -> 1100 , 1 -> 0011 ) if the input to block DSSS is [0 1] so the output of DSSS with DSSS=4 => [11000011] right?!

    thanks alot ,

  • 0 in reply to Ryan Maroun
    TI__Guru**** 317180 points

    LRM is well documented in the app note and the book we have linked to. It's also very easy to test how the data looks like in the receive chain by changing the data  you send. Send [0 1] and [1 0] and observe the difference if you are in doubt. Based on the information you have received so far it should be fully possible to compete your assignment. We are not going to do the assignment for you. The recommended usage is to let the chip do the decoding and hence your use case has limited interest for others.