Peter Scholtens / Mbed 2 deprecated SimpleDecimationFilter

A simple example.

Dependencies:   mbed FastIO

How does it work?

Oversampling

The core loop of the sampling does only one thing: it continuously looks at the input pin and increments a counter. Only when the input toggles, the counter value is used as an index and the histogram is updated and the counter is reset. By doing so the histogram will contain the run length of observed zeroes or ones, expressed in the time grid of the sampler. For a 1MHz bit stream the LPC 1768 should be capable to over sample approximately four times.

Grouping of run length

A filled histogram of run lengths, of both the zero and one symbols, will contain groups of adjacent run lengths values separated by empty spaces. If the sigma delta is connected to an analog voltage at exactly 25% of the range, the output pattern of the bit stream, expressed in the time grid of the ADC, will be close to 000100001000100001000100001... With approximately four times oversampling the LPC board may capture a data stream like: 0000, or expressed in run lengths: 10, 4, 16, 3, 12, 3, 15, 3, 11, 3, 16, 4. The histogram of zeroes will be filled with 1 at positions 10, 11, 12, 15 and 16, while the histogram of ones will be filled with 4 and 2 respectively at position 3 and 4.

Assign values to groups

After captured the data, the histogram will be scanned for groups of adjacent run lengths. A begin and end pointer/index of each will be stored in object type "Recovered". Once the whole histogram is scanned, a list of run length groups is determined. For each groups the average value of the run length will be determined.

Calculate Over Sample Ratio and Offset

The minimum distance between two average values will be a reasonable accurate value of the over sample factor. In our example the group of symbols consists of ADC run lengths of:

  • one: occurs 4 times with length 3 and 2 times 4, thus the average is 3.333.
  • three: consists of 11, 12 and 13 and thus an average of 12.0.
  • four: consists of one time 15 and two times 16: average equals 15.666.

The average distance between one and three is now 8.666. Therefore the average distance between three and four, only 3.666, a reasonable approximation of the over sample ratio. When acquiring more data, the average values will approximate the oversampling ratio better. An alternative method would be two take the shortest symbol as a value of the oversample factor, as this is the unit. However, as the loop requires some pre-processing before actively it can start counting, the average run length of the symbol with run length one will always be to lower than the actual over sample ratio. This creates an offset in the correlation of bit stream symbol to over sample data..

Known limitations

  • The amount of samples is only approximated, or more accurate, taken as a minimum value. As only the counter is compared once a complete run length of the same symbols is seen, it will be always slightly above the require value.
  • The amount of samples taken is hard coded. No means to vary this while running the application.
  • When the ADC input is very close or the maximum input voltage (or very close tot the minimum input voltage) the resulting bit stream will contain mostly very long run length of one's and hardly any zero (or vice versa). As no clock is connected, the stream may become out of synchronization for these cases.
  • Only the DC level is calculated, as a sum of all ones divided by the amount of symbols. Technically one could add Fourier transform in the post-processing and calculate SNR, THD, SINAD, ENOB etc, This requires another data structure of the histogram: store run length in the sequence they appear.
  • The algorithm works only correct given two assumptions. There should be exactly one group of empty spaces between two groups of captured run lengths (each representing a different bit stream run length). And each group of run lengths may not contain any empty position. Another decoder http://en.wikipedia.org/wiki/Viterbi_algorithm would possibly do better and even could estimate a qualification number.

main.cpp@7:5141bd76b08d, 2015-04-22 (annotated)

Committer:
pscholtens
Date:
Wed Apr 22 18:15:20 2015 +0000
Revision:
7:5141bd76b08d
Parent:
6:a5fc4e2ff34b
Child:
8:38175daee62b
Version 0.1.0 More sophisticated recovery of symbols. Should extend duty cycle range from [1/3,2/3] to almost full scale [1/128,127/128].

Who changed what in which revision?

UserRevisionLine numberNew contents of line
pscholtens 0:dc1b041f713e 1 #include "mbed.h"
pscholtens 0:dc1b041f713e 2
pscholtens 7:5141bd76b08d 3 /* version 0.1.0, P.C.S. Scholtens, Datang NXP, April 22th 2015, Nijmegen, Netherlands
pscholtens 7:5141bd76b08d 4 - Added more sophisticated method to find the correct symbol values. This one should
pscholtens 7:5141bd76b08d 5 be able to interpret the signals even if not all intermediate run length are present.
pscholtens 7:5141bd76b08d 6 This extends the usable input duty cycle range from [1/3,2/3] to [1/128, 127/128],
pscholtens 7:5141bd76b08d 7 if neither analog performance nor timing quantization errors create interference.
pscholtens 7:5141bd76b08d 8 */
pscholtens 7:5141bd76b08d 9
pscholtens 6:a5fc4e2ff34b 10 /* version 0.0.9, P.C.S. Scholtens, Datang NXP, April 21th 2015, Nijmegen, Netherlands
pscholtens 6:a5fc4e2ff34b 11 - Run time counter overflow fill now continue looking for same bit, however
pscholtens 6:a5fc4e2ff34b 12 clipping the actual store value. This prevents underflow occurence of other symbol
pscholtens 6:a5fc4e2ff34b 13 and may create lock if no bitstream is present.
pscholtens 6:a5fc4e2ff34b 14 - Time out function added to prevent lock in case no bitstream is present.
pscholtens 6:a5fc4e2ff34b 15 - Timer object renamed for clarity from t to timer, see http://xkcd.org/1513/
pscholtens 6:a5fc4e2ff34b 16 - Includes updated build of library mbed.
pscholtens 6:a5fc4e2ff34b 17 - Out-of-range of run length moved outside core loop, to speed up bitstream sampling
pscholtens 6:a5fc4e2ff34b 18 and consequently improving accuracy.
pscholtens 6:a5fc4e2ff34b 19 */
pscholtens 6:a5fc4e2ff34b 20
pscholtens 5:1c0bfd69719f 21 /* version 0.0.8, P.C.S. Scholtens, Datang NXP, April 17th 2015, Shanghai, PR China
pscholtens 5:1c0bfd69719f 22 - Corrected assigned synchronized values, as the first appearance wasn't assigned.
pscholtens 5:1c0bfd69719f 23 */
pscholtens 5:1c0bfd69719f 24
pscholtens 4:27a2eaee71ac 25 /* version 0.0.7, P.C.S. Scholtens, Datang NXP, April 16/17th 2015, Shanghai, PR China
pscholtens 4:27a2eaee71ac 26 - Method written to assign synchronized values to run-length.
pscholtens 4:27a2eaee71ac 27 - Added warnings for underflow.
pscholtens 4:27a2eaee71ac 28 - After skipped run-in cycles, copy the current bit, to prevent false single hit.
pscholtens 4:27a2eaee71ac 29 */
pscholtens 4:27a2eaee71ac 30
pscholtens 4:27a2eaee71ac 31 /* version 0.0.6, P.C.S. Scholtens, Datang NXP, April 15th, 2015, Shanghai, PR China
pscholtens 3:8d13bf073e92 32 - Corrected duty-cycle output for actual value of symbols (Thanks to Richard Zhu!).
pscholtens 3:8d13bf073e92 33 - Skipped run-in cycles to avoid pollution of the histogram with the first, most
pscholtens 3:8d13bf073e92 34 likely partial, sequence captured.
pscholtens 3:8d13bf073e92 35 - Added warnings for overflow.
pscholtens 3:8d13bf073e92 36 */
pscholtens 3:8d13bf073e92 37
pscholtens 2:5e37831540c7 38 /* version 0.0.5, P.C.S. Scholtens, Datang NXP, April 14th, 2015, Shanghai, PR China
pscholtens 3:8d13bf073e92 39 Implement histogram to find run lengths of zeroes and ones. */
pscholtens 2:5e37831540c7 40
pscholtens 1:2551859fbc25 41 /* version 0.0.4, P.C.S. Scholtens, Datang NXP, April 14th, 2015, Shanghai, PR China
pscholtens 1:2551859fbc25 42 Implement histogram to find run lengths of zroes and ones. */
pscholtens 1:2551859fbc25 43
pscholtens 1:2551859fbc25 44 /* version 0.0.3, P.C.S. Scholtens, Datang NXP, April 14th, 2015, Shanghai, PR China
pscholtens 6:a5fc4e2ff34b 45 Initial version. No synchronization of the symbols is done. */
pscholtens 0:dc1b041f713e 46
pscholtens 0:dc1b041f713e 47 /* See also:
pscholtens 0:dc1b041f713e 48 https://developer.mbed.org/forum/bugs-suggestions/topic/3464/
pscholtens 0:dc1b041f713e 49 */
pscholtens 0:dc1b041f713e 50
pscholtens 1:2551859fbc25 51 #define DEPTH 128
pscholtens 6:a5fc4e2ff34b 52 #define WATCH_DOG_TIME 4
pscholtens 1:2551859fbc25 53
pscholtens 1:2551859fbc25 54 /* Reserve memory space for the histogram */
pscholtens 1:2551859fbc25 55 unsigned int zeros[DEPTH];
pscholtens 1:2551859fbc25 56 unsigned int ones[DEPTH];
pscholtens 4:27a2eaee71ac 57 unsigned int assign[DEPTH];
pscholtens 1:2551859fbc25 58
pscholtens 6:a5fc4e2ff34b 59 DigitalIn bitstream(p11);
pscholtens 0:dc1b041f713e 60 DigitalOut myled(LED1);
pscholtens 6:a5fc4e2ff34b 61 Serial pc(USBTX, USBRX); // tx, rx
pscholtens 6:a5fc4e2ff34b 62 Timer timer;
pscholtens 6:a5fc4e2ff34b 63 Timeout timeout;
pscholtens 0:dc1b041f713e 64
pscholtens 7:5141bd76b08d 65 class Recovered {
pscholtens 7:5141bd76b08d 66 public:
pscholtens 7:5141bd76b08d 67 Recovered();
pscholtens 7:5141bd76b08d 68 virtual ~Recovered();
pscholtens 7:5141bd76b08d 69 float average;
pscholtens 7:5141bd76b08d 70 void calc_average();
pscholtens 7:5141bd76b08d 71 unsigned int index_start;
pscholtens 7:5141bd76b08d 72 unsigned int index_stop;
pscholtens 7:5141bd76b08d 73 unsigned int assigned_val;
pscholtens 7:5141bd76b08d 74 Recovered *next;
pscholtens 7:5141bd76b08d 75 private:
pscholtens 7:5141bd76b08d 76 };
pscholtens 7:5141bd76b08d 77
pscholtens 7:5141bd76b08d 78 /* Constructor */
pscholtens 7:5141bd76b08d 79 Recovered::Recovered()
pscholtens 7:5141bd76b08d 80 {
pscholtens 7:5141bd76b08d 81 next = NULL;
pscholtens 7:5141bd76b08d 82 };
pscholtens 7:5141bd76b08d 83
pscholtens 7:5141bd76b08d 84
pscholtens 7:5141bd76b08d 85 /* Destructor */
pscholtens 7:5141bd76b08d 86 Recovered::~Recovered()
pscholtens 7:5141bd76b08d 87 {
pscholtens 7:5141bd76b08d 88 if (next != NULL)
pscholtens 7:5141bd76b08d 89 delete next;
pscholtens 7:5141bd76b08d 90 };
pscholtens 7:5141bd76b08d 91
pscholtens 7:5141bd76b08d 92 /* Calculate average function, only call when index start and stop are defined. */
pscholtens 7:5141bd76b08d 93 void Recovered::calc_average()
pscholtens 7:5141bd76b08d 94 {
pscholtens 7:5141bd76b08d 95 unsigned int index = index_start;
pscholtens 7:5141bd76b08d 96 unsigned int sum;
pscholtens 7:5141bd76b08d 97 unsigned int amount = 0;
pscholtens 7:5141bd76b08d 98 float avg = 0;
pscholtens 7:5141bd76b08d 99 /* Test assumptions */
pscholtens 7:5141bd76b08d 100 if (index_start > DEPTH-1 ) pc.printf("ERROR: start value to high in average function.\n");
pscholtens 7:5141bd76b08d 101 if (index_stop > DEPTH-1 ) pc.printf("ERROR: stop value to high in average function.\n");
pscholtens 7:5141bd76b08d 102 if (index_start > index_stop) pc.printf("ERROR: start value beyond stop value in average function.\n");
pscholtens 7:5141bd76b08d 103 /* Core function */
pscholtens 7:5141bd76b08d 104 while (index < index_stop) {
pscholtens 7:5141bd76b08d 105 sum = zeros[index]+ones[index];
pscholtens 7:5141bd76b08d 106 amount += sum;
pscholtens 7:5141bd76b08d 107 avg += index*sum;
pscholtens 7:5141bd76b08d 108 index++;
pscholtens 7:5141bd76b08d 109 };
pscholtens 7:5141bd76b08d 110 avg /= amount;
pscholtens 7:5141bd76b08d 111 return;
pscholtens 7:5141bd76b08d 112 };
pscholtens 7:5141bd76b08d 113
pscholtens 1:2551859fbc25 114 /* A function to clear the contents of both histograms */
pscholtens 1:2551859fbc25 115 void clear_histogram() {
pscholtens 1:2551859fbc25 116 for(unsigned int i = 0; i < DEPTH; i++) {
pscholtens 1:2551859fbc25 117 zeros[i] = 0;
pscholtens 1:2551859fbc25 118 ones[i] = 0;
pscholtens 1:2551859fbc25 119 }
pscholtens 1:2551859fbc25 120 }
pscholtens 1:2551859fbc25 121
pscholtens 1:2551859fbc25 122 /* Print the contents of the histogram, excluding the empty values */
pscholtens 1:2551859fbc25 123 void print_histogram() {
pscholtens 4:27a2eaee71ac 124 pc.printf(" Sequence Zeros Ones Assign\n");
pscholtens 4:27a2eaee71ac 125 if ( zeros[0]+ones[0] != 0 ) {
pscholtens 4:27a2eaee71ac 126 pc.printf("Underflow %8i %8i\n",zeros[0],ones[0]);
pscholtens 4:27a2eaee71ac 127 }
pscholtens 4:27a2eaee71ac 128 for (unsigned int i = 1; i < DEPTH-1; i++) {
pscholtens 1:2551859fbc25 129 if ( zeros[i]+ones[i] != 0 ) {
pscholtens 4:27a2eaee71ac 130 pc.printf(" %8i %8i %8i %8i\n",i,zeros[i],ones[i],assign[i]);
pscholtens 1:2551859fbc25 131 }
pscholtens 1:2551859fbc25 132 }
pscholtens 3:8d13bf073e92 133 if ( zeros[DEPTH-1]+ones[DEPTH-1] != 0 ) {
pscholtens 4:27a2eaee71ac 134 pc.printf("Overflow %8i %8i\n",zeros[DEPTH-1],ones[DEPTH-1]);
pscholtens 3:8d13bf073e92 135 }
pscholtens 3:8d13bf073e92 136
pscholtens 1:2551859fbc25 137 }
pscholtens 1:2551859fbc25 138
pscholtens 6:a5fc4e2ff34b 139 /* Will only be called if measurement time exceeds preset watch dog timer. */
pscholtens 6:a5fc4e2ff34b 140 void at_time_out() {
pscholtens 6:a5fc4e2ff34b 141 pc.printf("Input clipped to level %i, no bitstream present.\n", (int) bitstream);
pscholtens 6:a5fc4e2ff34b 142 timeout.attach(&at_time_out, WATCH_DOG_TIME);
pscholtens 6:a5fc4e2ff34b 143 }
pscholtens 6:a5fc4e2ff34b 144
pscholtens 1:2551859fbc25 145 /* Function which fill the histogram */
pscholtens 1:2551859fbc25 146 void fill_histogram(unsigned int num_unsync_samples) {
pscholtens 1:2551859fbc25 147 unsigned int count = 0;
pscholtens 1:2551859fbc25 148 unsigned int run_length = 0;
pscholtens 2:5e37831540c7 149 bool previous_bit = (bool) bitstream;
pscholtens 6:a5fc4e2ff34b 150 /* Switch on watch dog timer */
pscholtens 6:a5fc4e2ff34b 151 timeout.attach(&at_time_out, WATCH_DOG_TIME);
pscholtens 3:8d13bf073e92 152 /* Implements run-in: skip the first sequence as it is only a partial one. */
pscholtens 6:a5fc4e2ff34b 153 while(previous_bit == (bool) bitstream) {
pscholtens 6:a5fc4e2ff34b 154 /* Do nothing, intentionally */;
pscholtens 3:8d13bf073e92 155 };
pscholtens 4:27a2eaee71ac 156 previous_bit = !previous_bit;
pscholtens 3:8d13bf073e92 157 run_length = 0;
pscholtens 6:a5fc4e2ff34b 158 /* Start actual counting here, store in variable run_length (will be clipped to DEPTH) */
pscholtens 1:2551859fbc25 159 while(count < num_unsync_samples) {
pscholtens 6:a5fc4e2ff34b 160 /* Core of the loop */
pscholtens 6:a5fc4e2ff34b 161 while(previous_bit == (bool) bitstream) {
pscholtens 1:2551859fbc25 162 run_length++;
pscholtens 1:2551859fbc25 163 };
pscholtens 6:a5fc4e2ff34b 164 /* Increment counter before clipping to preserve accuracy. */
pscholtens 6:a5fc4e2ff34b 165 count += run_length;
pscholtens 6:a5fc4e2ff34b 166 /* Test if run length exceeds depth of histogram, if so assign clip value. */
pscholtens 6:a5fc4e2ff34b 167 if (run_length < DEPTH-1) {
pscholtens 6:a5fc4e2ff34b 168 run_length = DEPTH-1;
pscholtens 6:a5fc4e2ff34b 169 }
pscholtens 6:a5fc4e2ff34b 170 /* Now write in histogram array of interest */
pscholtens 1:2551859fbc25 171 if (previous_bit) {
pscholtens 1:2551859fbc25 172 ones[run_length]++;
pscholtens 1:2551859fbc25 173 }
pscholtens 1:2551859fbc25 174 else {
pscholtens 1:2551859fbc25 175 zeros[run_length]++;
pscholtens 1:2551859fbc25 176 }
pscholtens 6:a5fc4e2ff34b 177 /* Reset for next run length counting loop */
pscholtens 2:5e37831540c7 178 run_length = 0;
pscholtens 2:5e37831540c7 179 previous_bit = !previous_bit;
pscholtens 1:2551859fbc25 180 }
pscholtens 6:a5fc4e2ff34b 181 /* Switch off watch dog timer */
pscholtens 6:a5fc4e2ff34b 182 timeout.detach();
pscholtens 1:2551859fbc25 183 }
pscholtens 1:2551859fbc25 184
pscholtens 1:2551859fbc25 185 /* Here we count the number of unsynchronized symbols, mimicing previous implementation */
pscholtens 1:2551859fbc25 186 unsigned int get_num_unsync_symbols(int symbol) {
pscholtens 1:2551859fbc25 187 unsigned int sum = 0;
pscholtens 1:2551859fbc25 188 for (unsigned int i = 0; i < DEPTH; i++) {
pscholtens 1:2551859fbc25 189 if (symbol == 0) {
pscholtens 1:2551859fbc25 190 sum += zeros[i];
pscholtens 1:2551859fbc25 191 } else {
pscholtens 1:2551859fbc25 192 sum += ones[i];
pscholtens 1:2551859fbc25 193 }
pscholtens 1:2551859fbc25 194 }
pscholtens 1:2551859fbc25 195 return sum;
pscholtens 1:2551859fbc25 196 }
pscholtens 1:2551859fbc25 197
pscholtens 3:8d13bf073e92 198 /* Calculate the value, using the unsynchronized method */
pscholtens 3:8d13bf073e92 199 unsigned int get_value_unsync_symbols(int symbol) {
pscholtens 3:8d13bf073e92 200 unsigned int sum = 0;
pscholtens 3:8d13bf073e92 201 for (unsigned int i = 0; i < DEPTH; i++) {
pscholtens 3:8d13bf073e92 202 if (symbol == 0) {
pscholtens 3:8d13bf073e92 203 sum += i*zeros[i];
pscholtens 3:8d13bf073e92 204 } else {
pscholtens 3:8d13bf073e92 205 sum += i*ones[i];
pscholtens 3:8d13bf073e92 206 }
pscholtens 3:8d13bf073e92 207 }
pscholtens 3:8d13bf073e92 208 return sum;
pscholtens 3:8d13bf073e92 209 }
pscholtens 3:8d13bf073e92 210
pscholtens 4:27a2eaee71ac 211 /* Calculate the value, using the synchronization algorithm */
pscholtens 4:27a2eaee71ac 212 unsigned int get_value_synced_symbols(int symbol) {
pscholtens 4:27a2eaee71ac 213 bool presence = false;
pscholtens 4:27a2eaee71ac 214 int value = 0;
pscholtens 4:27a2eaee71ac 215 for (unsigned int i = 0; i < DEPTH; i++) {
pscholtens 4:27a2eaee71ac 216 if ( zeros[i]+ones[i] != 0 ) {
pscholtens 4:27a2eaee71ac 217 if (presence) {
pscholtens 5:1c0bfd69719f 218 assign[i] = value;
pscholtens 4:27a2eaee71ac 219 } else {
pscholtens 4:27a2eaee71ac 220 value++;
pscholtens 5:1c0bfd69719f 221 presence = true;
pscholtens 5:1c0bfd69719f 222 assign[i] = value;
pscholtens 4:27a2eaee71ac 223 }
pscholtens 4:27a2eaee71ac 224 } else {
pscholtens 4:27a2eaee71ac 225 presence = false;
pscholtens 4:27a2eaee71ac 226 }
pscholtens 4:27a2eaee71ac 227 }
pscholtens 4:27a2eaee71ac 228 /* Now do the actual summation of symbol values */
pscholtens 4:27a2eaee71ac 229 unsigned int sum = 0;
pscholtens 4:27a2eaee71ac 230 for (unsigned int i = 0; i < DEPTH; i++) {
pscholtens 4:27a2eaee71ac 231 if (symbol == 0) {
pscholtens 4:27a2eaee71ac 232 sum += assign[i]*zeros[i];
pscholtens 4:27a2eaee71ac 233 } else {
pscholtens 4:27a2eaee71ac 234 sum += assign[i]*ones[i];
pscholtens 4:27a2eaee71ac 235 }
pscholtens 4:27a2eaee71ac 236 }
pscholtens 4:27a2eaee71ac 237 return sum;
pscholtens 4:27a2eaee71ac 238 }
pscholtens 4:27a2eaee71ac 239
pscholtens 7:5141bd76b08d 240 /* Calculate the value, using the new synchronization algorithm */
pscholtens 7:5141bd76b08d 241 float get_dutycycle_synced_symbols_new_method() {
pscholtens 7:5141bd76b08d 242 /* First step (第一步): scan areas of non-zero content in histogram, starting at first non-overflow sequence at the end */
pscholtens 7:5141bd76b08d 243 bool presence = false;
pscholtens 7:5141bd76b08d 244 Recovered *list = NULL;
pscholtens 7:5141bd76b08d 245 Recovered *first = NULL;
pscholtens 7:5141bd76b08d 246 for (signed int i = DEPTH-2; i > -1 ; i--) {
pscholtens 7:5141bd76b08d 247 if ( zeros[i]+ones[i] != 0 ) {
pscholtens 7:5141bd76b08d 248 if (presence) {
pscholtens 7:5141bd76b08d 249 first->index_start = i;
pscholtens 7:5141bd76b08d 250 } else {
pscholtens 7:5141bd76b08d 251 /* Create new Recovered symbol and position it at the beginning of the list of dis(/re)covered symbols */
pscholtens 7:5141bd76b08d 252 first = new Recovered;
pscholtens 7:5141bd76b08d 253 first->next = list;
pscholtens 7:5141bd76b08d 254 first->index_stop = i+1;
pscholtens 7:5141bd76b08d 255 list = first;
pscholtens 7:5141bd76b08d 256 presence = true;
pscholtens 7:5141bd76b08d 257 }
pscholtens 7:5141bd76b08d 258 } else {
pscholtens 7:5141bd76b08d 259 presence = false;
pscholtens 7:5141bd76b08d 260 }
pscholtens 7:5141bd76b08d 261 }
pscholtens 7:5141bd76b08d 262 /* Step two (第二步): for each found area, calculate average values */
pscholtens 7:5141bd76b08d 263 Recovered* index = list;
pscholtens 7:5141bd76b08d 264 while (index != NULL) {
pscholtens 7:5141bd76b08d 265 index->calc_average();
pscholtens 7:5141bd76b08d 266 index = index->next;
pscholtens 7:5141bd76b08d 267 }
pscholtens 7:5141bd76b08d 268 /* Step three (第三步): Find smallest distance between two adjacent symbols, e.g. with run length of 0.91, 6.99, 8.01, the last two define the grid/oversample ratio. */
pscholtens 7:5141bd76b08d 269 float oversample = DEPTH;
pscholtens 7:5141bd76b08d 270 Recovered* cmp1 = list;
pscholtens 7:5141bd76b08d 271 Recovered* cmp2 = list->next;
pscholtens 7:5141bd76b08d 272 if (list != NULL) {
pscholtens 7:5141bd76b08d 273 while (cmp2 != NULL) {
pscholtens 7:5141bd76b08d 274 float diff = cmp2->average-cmp1->average;
pscholtens 7:5141bd76b08d 275 if (diff < oversample) {
pscholtens 7:5141bd76b08d 276 oversample = diff;
pscholtens 7:5141bd76b08d 277 }
pscholtens 7:5141bd76b08d 278 cmp1=cmp2;
pscholtens 7:5141bd76b08d 279 cmp2=cmp1->next;
pscholtens 7:5141bd76b08d 280 }
pscholtens 7:5141bd76b08d 281 }
pscholtens 7:5141bd76b08d 282 /* Step four (第四步): Divide the average run length of all found recovered symbol by the found oversample ratio. */
pscholtens 7:5141bd76b08d 283 index = list;
pscholtens 7:5141bd76b08d 284 while (index != NULL) {
pscholtens 7:5141bd76b08d 285 index->average /= oversample;
pscholtens 7:5141bd76b08d 286 index = index->next;
pscholtens 7:5141bd76b08d 287 }
pscholtens 7:5141bd76b08d 288
pscholtens 7:5141bd76b08d 289 /* Step five (第五步): find offset and remove it (Assumption that there are always symbol with run length 1 ) */
pscholtens 7:5141bd76b08d 290 index = list;
pscholtens 7:5141bd76b08d 291 float offset = oversample-index->average;
pscholtens 7:5141bd76b08d 292 while (index != NULL) {
pscholtens 7:5141bd76b08d 293 index->average -= offset;
pscholtens 7:5141bd76b08d 294 index = index->next;
pscholtens 7:5141bd76b08d 295 }
pscholtens 4:27a2eaee71ac 296
pscholtens 7:5141bd76b08d 297 /* Step six (第六步): round to nearest integer and assign value to both arrays */
pscholtens 7:5141bd76b08d 298 index = list;
pscholtens 7:5141bd76b08d 299 while (index != NULL) {
pscholtens 7:5141bd76b08d 300 index->assigned_val = (int) (index->average+0.5);
pscholtens 7:5141bd76b08d 301 for (int i = index->index_start; i < index->index_stop; i++ ) {
pscholtens 7:5141bd76b08d 302 assign[i] = index->assigned_val;
pscholtens 7:5141bd76b08d 303 }
pscholtens 7:5141bd76b08d 304 index = index->next;
pscholtens 7:5141bd76b08d 305 }
pscholtens 7:5141bd76b08d 306
pscholtens 7:5141bd76b08d 307 /* Step seven (第七步): Now do the actual summation of symbol values */
pscholtens 7:5141bd76b08d 308 unsigned int sum0 = 0, sum1 = 0;
pscholtens 7:5141bd76b08d 309 for (unsigned int i = 0; i < DEPTH; i++) {
pscholtens 7:5141bd76b08d 310 sum0 += assign[i]*zeros[i];
pscholtens 7:5141bd76b08d 311 sum1 += assign[i]*ones[i];
pscholtens 7:5141bd76b08d 312 }
pscholtens 7:5141bd76b08d 313 /* Step eight (第八步): Delete the recovered symbol object to clear memory. As a destructor is defined
pscholtens 7:5141bd76b08d 314 this will be automatically handled recursively. And of course return the duty cycle */
pscholtens 7:5141bd76b08d 315 delete list;
pscholtens 7:5141bd76b08d 316 return ((float) sum0)/sum1;
pscholtens 7:5141bd76b08d 317 }
pscholtens 7:5141bd76b08d 318
pscholtens 7:5141bd76b08d 319 /* The main (主程序) routine of the program */
pscholtens 1:2551859fbc25 320
pscholtens 0:dc1b041f713e 321 int main() {
pscholtens 7:5141bd76b08d 322 unsigned int num_of_zeros, num_of_ones, value_of_unsync_zeros, value_of_unsync_ones, value_of_synced_zeros, value_of_synced_ones,
pscholtens 7:5141bd76b08d 323 sum_of_unsync_symbols, sum_of_synced_symbols;
pscholtens 7:5141bd76b08d 324 float unsync_dutycycle, synced_dutycycle, unsync_voltage, synced_voltage, synced_dutycycle_new, synced_voltage_new;
pscholtens 1:2551859fbc25 325 pc.baud(115200);
pscholtens 7:5141bd76b08d 326 pc.printf("Bitstream counter, version 0.1.0, P.C.S. Scholtens, April 22th 2015, Nijmegen, Netherlands.\n");
pscholtens 6:a5fc4e2ff34b 327 pc.printf("Build " __DATE__ " " __TIME__ "\n");
pscholtens 0:dc1b041f713e 328 /*LPC_TIM2->PR = 0x0000002F; / * decimal 47 */
pscholtens 0:dc1b041f713e 329 /*LPC_TIM3->PR = 24;*/
pscholtens 1:2551859fbc25 330 clear_histogram();
pscholtens 0:dc1b041f713e 331 while(1) {
pscholtens 6:a5fc4e2ff34b 332 timer.reset();
pscholtens 0:dc1b041f713e 333 myled = 1;
pscholtens 1:2551859fbc25 334 clear_histogram();
pscholtens 6:a5fc4e2ff34b 335 timer.start();
pscholtens 5:1c0bfd69719f 336 fill_histogram(1e7);
pscholtens 6:a5fc4e2ff34b 337 timer.stop();
pscholtens 4:27a2eaee71ac 338 pc.printf("\n------ Captured Histogram ------\n");
pscholtens 1:2551859fbc25 339 print_histogram();
pscholtens 1:2551859fbc25 340 num_of_zeros = get_num_unsync_symbols(0);
pscholtens 1:2551859fbc25 341 num_of_ones = get_num_unsync_symbols(1);
pscholtens 3:8d13bf073e92 342 value_of_unsync_zeros = get_value_unsync_symbols(0);
pscholtens 3:8d13bf073e92 343 value_of_unsync_ones = get_value_unsync_symbols(1);
pscholtens 7:5141bd76b08d 344 sum_of_unsync_symbols = value_of_unsync_zeros+value_of_unsync_ones;
pscholtens 7:5141bd76b08d 345 unsync_dutycycle = ((float) value_of_unsync_ones)/sum_of_unsync_symbols; /* We need to typecast one of the integers to float, otherwise the result is rounded till zero. */
pscholtens 3:8d13bf073e92 346 unsync_voltage = (0.5*13*unsync_dutycycle+1)*0.9; /* This is the ADC formula, see analysisSigmaDeltaADC.pdf */
pscholtens 4:27a2eaee71ac 347 value_of_synced_zeros = get_value_synced_symbols(0);
pscholtens 4:27a2eaee71ac 348 value_of_synced_ones = get_value_synced_symbols(1);
pscholtens 7:5141bd76b08d 349 sum_of_synced_symbols = value_of_synced_zeros+value_of_synced_ones;
pscholtens 7:5141bd76b08d 350 synced_dutycycle = ((float) value_of_synced_ones)/sum_of_synced_symbols; /* We need to typecast one of the integers to float, otherwise the result is rounded till zero. */
pscholtens 4:27a2eaee71ac 351 synced_voltage = (0.5*13*synced_dutycycle+1)*0.9; /* This is the ADC formula, see analysisSigmaDeltaADC.pdf */
pscholtens 7:5141bd76b08d 352 synced_dutycycle_new = get_dutycycle_synced_symbols_new_method();
pscholtens 7:5141bd76b08d 353 synced_voltage_new = (0.5*13*synced_dutycycle+1)*0.9; /* This is the ADC formula, see analysisSigmaDeltaADC.pdf */
pscholtens 4:27a2eaee71ac 354 pc.printf("------ Unsynchronized Results ------\n");
pscholtens 4:27a2eaee71ac 355 pc.printf("Counted Sequences %8i %8i\n", num_of_zeros , num_of_ones);
pscholtens 4:27a2eaee71ac 356 pc.printf("Summed Values %8i %8i\n", value_of_unsync_zeros, value_of_unsync_ones);
pscholtens 4:27a2eaee71ac 357 pc.printf("Duty Cycle %f, equals %f Volt\n", unsync_dutycycle , unsync_voltage);
pscholtens 4:27a2eaee71ac 358 pc.printf("------ Synchronized Results ------\n");
pscholtens 4:27a2eaee71ac 359 pc.printf("Summed Values %8i %8i\n", value_of_synced_zeros, value_of_synced_ones);
pscholtens 4:27a2eaee71ac 360 pc.printf("Duty Cyle %f, equals %f Volt\n", synced_dutycycle , synced_voltage);
pscholtens 7:5141bd76b08d 361 pc.printf("----- Synchronized Results NEW -----\n");
pscholtens 7:5141bd76b08d 362 pc.printf("Duty Cyle %f, equals %f Volt\n", synced_dutycycle_new , synced_voltage_new);
pscholtens 4:27a2eaee71ac 363 pc.printf("------------------------------------\n");
pscholtens 6:a5fc4e2ff34b 364 pc.printf("Measured in %f sec.\n", timer.read());
pscholtens 4:27a2eaee71ac 365 pc.printf("====================================\n");
pscholtens 0:dc1b041f713e 366 myled = 0;
pscholtens 5:1c0bfd69719f 367 wait(0.1);
pscholtens 0:dc1b041f713e 368 }
pscholtens 4:27a2eaee71ac 369 }