1. Lab 4 Instructions By Yeong Choo and Sam Kanawati
The University of Texas at Austin, March 19, 2018

2. DSK Implementation of PN Sequence Generation
Create a talk-through project in CCS such as in Lab 1 introductory lab.
Inside ISRs.c, please comment out the following lines:
xLeft = CodecDataIn.Channel[ LEFT];
xRight = CodecDataIn.Channel[ RIGHT];
yLeft = xLeft;
yRight = xRight;
Also inside ISRs.c, please do the following:
Implement a PN sequence generator with SSRG [5,2]s where 2nd and 5th taps are the feedbacks
Represent the SSRG state as a single integer variable:
Declare int SSRG_state; to represent up to 32-bit state, or declare long long SSRG_state; to represent 64-bit state
Create a function prototype that does the following:
Update SSRG [5,2]s next state and return a newest bit
   i.e. y[n] = y[n-2] + y[n-5] mod 2
Inputs: pointer to state variable
Output: newest bit at time n
Implement int SSRG_update (int * state_ptrn);
Leverage on bitwise operations (&, |, ^) and logical operations (<<, >>)
Set initial condition of the SSRG_state to any value of range {1, …, 2 5 −1}
Pass current output bit to Serial Port Codec such as the following:
#define A 32000 …
CodecDataOut.Channel[ LEFT] = A*((SSRG_state >> 4)&1);
WriteCodecData(CodecDataOut.UINT);
Note that SSRG_state has the oldest bit in the least significant bit, modify your code accordingly
Verify periodic operation of SSRG [5,2]s by observing the following:
Oscilloscope waveform (Include one screenshot in lab report)
Collect an array of first 100 states (Include one table in lab report)
For performance analysis
Profile your implementation of SSRG [5,2]s (Include one screenshot in lab report)

3. DSK Implementation of Data Scrambler and Data Descrambler
Implement data scrambling and data descrambling using the same SSRG [5,2]s
Represent the Data Scrambler and Data Descrambler states as two separate integer variables:
Declare int DS_state, DD_state; to represent up to 32-bit state
Modify the above implementation to take in input bit “in” such that int SSRG_update (int *state_ptr, int in);
Note that newest bit at time n to the Data Scrambler is function of bits to be sent and newest bit at time n-1
Pass the scrambled bit from Data Scrambler as an input to Data Descrambler
Run Data Scrambler followed by Data Descrambler once at every ISR execution
Send input vector to one channel of audio codec and data scrambler output to another channel of audio codec such as the following:
#define A 32000
#define input 1 …
int output;
CodecDataOut.Channel[ LEFT] = A*(input);
CodecDataOut.Channel[ RIGHT] = A*((DS_state >> 4) & 1);
WriteCodecData(CodecDataOut.UINT);
Note that this test uses constant input of 1 into data scrambler, to test your implementation, also use constant input of 0
Remember to update the DS_state and DD_state separately
A few notes on debugging:
To verify correct operation of data scrambler and descrambler, Input vector of all ones or all zeros.
Please note that the intermediate vector between Data Scrambler and Data Descrambler must be different than the input vector
Please verify that the output vector of data descrambler is exactly similar as the input vector
Collect an array of first 100 states of data scrambler and data descrambler (Include two tables in lab report)
Profile your implementation of data scrambler and data descrambler (Include two screenshots in lab report)

4. Autocorrelation Graphs
Find out the period of PN sequence from the array of first 100 states of SSRG [5,2]s
Verify that the experimental measurement of period matches the theoretical value
Generate an autocorrelation graph on two periods worth of PN sequence output bit
(Include one graph on lab report and supply all source code)
Generate an autocorrelation graph on two periods worth of data scrambler output bit
Don’t use Matlab Function call
Please implement the autocorrelation from scratch following the slide below
Expected output