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@9:8136aea421e3, 2015-04-30 (annotated)

Committer:
pscholtens
Date:
Thu Apr 30 06:34:56 2015 +0000
Revision:
9:8136aea421e3
Parent:
8:38175daee62b
Child:
10:42e390f304fc
Corrected output of new DC filter, still not working on bench.

Who changed what in which revision?

UserRevisionLine numberNew contents of line
pscholtens 0:dc1b041f713e 1 #include "mbed.h"
pscholtens 0:dc1b041f713e 2
pscholtens 8:38175daee62b 3 /* version 0.1.1, P.C.S. Scholtens, Datang NXP, April 24th 2015, Nijmegen, Netherlands
pscholtens 8:38175daee62b 4 - Average function did not return the calculated average, now repaired.
pscholtens 8:38175daee62b 5 - Offset was subtracted while it should be added to compensate loss of oversampling
pscholtens 8:38175daee62b 6 ratio in the first round of the core loop.
pscholtens 8:38175daee62b 7 - Misleading type cast set to final type as chosen by compiler.
pscholtens 8:38175daee62b 8 */
pscholtens 8:38175daee62b 9
pscholtens 7:5141bd76b08d 10 /* version 0.1.0, P.C.S. Scholtens, Datang NXP, April 22th 2015, Nijmegen, Netherlands
pscholtens 7:5141bd76b08d 11 - Added more sophisticated method to find the correct symbol values. This one should
pscholtens 7:5141bd76b08d 12 be able to interpret the signals even if not all intermediate run length are present.
pscholtens 7:5141bd76b08d 13 This extends the usable input duty cycle range from [1/3,2/3] to [1/128, 127/128],
pscholtens 7:5141bd76b08d 14 if neither analog performance nor timing quantization errors create interference.
pscholtens 7:5141bd76b08d 15 */
pscholtens 7:5141bd76b08d 16
pscholtens 6:a5fc4e2ff34b 17 /* version 0.0.9, P.C.S. Scholtens, Datang NXP, April 21th 2015, Nijmegen, Netherlands
pscholtens 6:a5fc4e2ff34b 18 - Run time counter overflow fill now continue looking for same bit, however
pscholtens 6:a5fc4e2ff34b 19 clipping the actual store value. This prevents underflow occurence of other symbol
pscholtens 6:a5fc4e2ff34b 20 and may create lock if no bitstream is present.
pscholtens 6:a5fc4e2ff34b 21 - Time out function added to prevent lock in case no bitstream is present.
pscholtens 6:a5fc4e2ff34b 22 - Timer object renamed for clarity from t to timer, see http://xkcd.org/1513/
pscholtens 6:a5fc4e2ff34b 23 - Includes updated build of library mbed.
pscholtens 6:a5fc4e2ff34b 24 - Out-of-range of run length moved outside core loop, to speed up bitstream sampling
pscholtens 6:a5fc4e2ff34b 25 and consequently improving accuracy.
pscholtens 6:a5fc4e2ff34b 26 */
pscholtens 6:a5fc4e2ff34b 27
pscholtens 5:1c0bfd69719f 28 /* version 0.0.8, P.C.S. Scholtens, Datang NXP, April 17th 2015, Shanghai, PR China
pscholtens 5:1c0bfd69719f 29 - Corrected assigned synchronized values, as the first appearance wasn't assigned.
pscholtens 5:1c0bfd69719f 30 */
pscholtens 5:1c0bfd69719f 31
pscholtens 4:27a2eaee71ac 32 /* version 0.0.7, P.C.S. Scholtens, Datang NXP, April 16/17th 2015, Shanghai, PR China
pscholtens 4:27a2eaee71ac 33 - Method written to assign synchronized values to run-length.
pscholtens 4:27a2eaee71ac 34 - Added warnings for underflow.
pscholtens 4:27a2eaee71ac 35 - After skipped run-in cycles, copy the current bit, to prevent false single hit.
pscholtens 4:27a2eaee71ac 36 */
pscholtens 4:27a2eaee71ac 37
pscholtens 4:27a2eaee71ac 38 /* version 0.0.6, P.C.S. Scholtens, Datang NXP, April 15th, 2015, Shanghai, PR China
pscholtens 3:8d13bf073e92 39 - Corrected duty-cycle output for actual value of symbols (Thanks to Richard Zhu!).
pscholtens 3:8d13bf073e92 40 - Skipped run-in cycles to avoid pollution of the histogram with the first, most
pscholtens 3:8d13bf073e92 41 likely partial, sequence captured.
pscholtens 3:8d13bf073e92 42 - Added warnings for overflow.
pscholtens 3:8d13bf073e92 43 */
pscholtens 3:8d13bf073e92 44
pscholtens 2:5e37831540c7 45 /* version 0.0.5, P.C.S. Scholtens, Datang NXP, April 14th, 2015, Shanghai, PR China
pscholtens 3:8d13bf073e92 46 Implement histogram to find run lengths of zeroes and ones. */
pscholtens 2:5e37831540c7 47
pscholtens 1:2551859fbc25 48 /* version 0.0.4, P.C.S. Scholtens, Datang NXP, April 14th, 2015, Shanghai, PR China
pscholtens 1:2551859fbc25 49 Implement histogram to find run lengths of zroes and ones. */
pscholtens 1:2551859fbc25 50
pscholtens 1:2551859fbc25 51 /* version 0.0.3, P.C.S. Scholtens, Datang NXP, April 14th, 2015, Shanghai, PR China
pscholtens 6:a5fc4e2ff34b 52 Initial version. No synchronization of the symbols is done. */
pscholtens 0:dc1b041f713e 53
pscholtens 0:dc1b041f713e 54 /* See also:
pscholtens 0:dc1b041f713e 55 https://developer.mbed.org/forum/bugs-suggestions/topic/3464/
pscholtens 9:8136aea421e3 56 To speed up, maybe bypass the mask function in the gpio_read function of file
pscholtens 9:8136aea421e3 57 ./mbed/targets/hal/TARGET_NXP/TARGET_LPC176X/gpio_object.h
pscholtens 9:8136aea421e3 58 from git
pscholtens 9:8136aea421e3 59 git clone https://github.com/mbedmicro/mbed.git
pscholtens 9:8136aea421e3 60
pscholtens 0:dc1b041f713e 61 */
pscholtens 0:dc1b041f713e 62
pscholtens 1:2551859fbc25 63 #define DEPTH 128
pscholtens 6:a5fc4e2ff34b 64 #define WATCH_DOG_TIME 4
pscholtens 1:2551859fbc25 65
pscholtens 1:2551859fbc25 66 /* Reserve memory space for the histogram */
pscholtens 1:2551859fbc25 67 unsigned int zeros[DEPTH];
pscholtens 1:2551859fbc25 68 unsigned int ones[DEPTH];
pscholtens 4:27a2eaee71ac 69 unsigned int assign[DEPTH];
pscholtens 1:2551859fbc25 70
pscholtens 6:a5fc4e2ff34b 71 DigitalIn bitstream(p11);
pscholtens 0:dc1b041f713e 72 DigitalOut myled(LED1);
pscholtens 6:a5fc4e2ff34b 73 Serial pc(USBTX, USBRX); // tx, rx
pscholtens 6:a5fc4e2ff34b 74 Timer timer;
pscholtens 6:a5fc4e2ff34b 75 Timeout timeout;
pscholtens 0:dc1b041f713e 76
pscholtens 7:5141bd76b08d 77 class Recovered {
pscholtens 7:5141bd76b08d 78 public:
pscholtens 7:5141bd76b08d 79 Recovered();
pscholtens 7:5141bd76b08d 80 virtual ~Recovered();
pscholtens 7:5141bd76b08d 81 float average;
pscholtens 7:5141bd76b08d 82 void calc_average();
pscholtens 7:5141bd76b08d 83 unsigned int index_start;
pscholtens 7:5141bd76b08d 84 unsigned int index_stop;
pscholtens 7:5141bd76b08d 85 unsigned int assigned_val;
pscholtens 7:5141bd76b08d 86 Recovered *next;
pscholtens 7:5141bd76b08d 87 private:
pscholtens 7:5141bd76b08d 88 };
pscholtens 7:5141bd76b08d 89
pscholtens 7:5141bd76b08d 90 /* Constructor */
pscholtens 7:5141bd76b08d 91 Recovered::Recovered()
pscholtens 7:5141bd76b08d 92 {
pscholtens 7:5141bd76b08d 93 next = NULL;
pscholtens 7:5141bd76b08d 94 };
pscholtens 7:5141bd76b08d 95
pscholtens 7:5141bd76b08d 96
pscholtens 7:5141bd76b08d 97 /* Destructor */
pscholtens 7:5141bd76b08d 98 Recovered::~Recovered()
pscholtens 7:5141bd76b08d 99 {
pscholtens 7:5141bd76b08d 100 if (next != NULL)
pscholtens 7:5141bd76b08d 101 delete next;
pscholtens 7:5141bd76b08d 102 };
pscholtens 7:5141bd76b08d 103
pscholtens 7:5141bd76b08d 104 /* Calculate average function, only call when index start and stop are defined. */
pscholtens 7:5141bd76b08d 105 void Recovered::calc_average()
pscholtens 7:5141bd76b08d 106 {
pscholtens 7:5141bd76b08d 107 unsigned int index = index_start;
pscholtens 7:5141bd76b08d 108 unsigned int sum;
pscholtens 7:5141bd76b08d 109 unsigned int amount = 0;
pscholtens 8:38175daee62b 110 average = 0;
pscholtens 7:5141bd76b08d 111 /* Test assumptions */
pscholtens 7:5141bd76b08d 112 if (index_start > DEPTH-1 ) pc.printf("ERROR: start value to high in average function.\n");
pscholtens 7:5141bd76b08d 113 if (index_stop > DEPTH-1 ) pc.printf("ERROR: stop value to high in average function.\n");
pscholtens 7:5141bd76b08d 114 if (index_start > index_stop) pc.printf("ERROR: start value beyond stop value in average function.\n");
pscholtens 7:5141bd76b08d 115 /* Core function */
pscholtens 7:5141bd76b08d 116 while (index < index_stop) {
pscholtens 8:38175daee62b 117 sum = zeros[index]+ones[index];
pscholtens 8:38175daee62b 118 amount += sum;
pscholtens 8:38175daee62b 119 average += index*sum;
pscholtens 7:5141bd76b08d 120 index++;
pscholtens 7:5141bd76b08d 121 };
pscholtens 8:38175daee62b 122 average /= amount;
pscholtens 7:5141bd76b08d 123 return;
pscholtens 7:5141bd76b08d 124 };
pscholtens 7:5141bd76b08d 125
pscholtens 1:2551859fbc25 126 /* A function to clear the contents of both histograms */
pscholtens 1:2551859fbc25 127 void clear_histogram() {
pscholtens 1:2551859fbc25 128 for(unsigned int i = 0; i < DEPTH; i++) {
pscholtens 1:2551859fbc25 129 zeros[i] = 0;
pscholtens 1:2551859fbc25 130 ones[i] = 0;
pscholtens 1:2551859fbc25 131 }
pscholtens 1:2551859fbc25 132 }
pscholtens 1:2551859fbc25 133
pscholtens 1:2551859fbc25 134 /* Print the contents of the histogram, excluding the empty values */
pscholtens 1:2551859fbc25 135 void print_histogram() {
pscholtens 4:27a2eaee71ac 136 pc.printf(" Sequence Zeros Ones Assign\n");
pscholtens 4:27a2eaee71ac 137 if ( zeros[0]+ones[0] != 0 ) {
pscholtens 4:27a2eaee71ac 138 pc.printf("Underflow %8i %8i\n",zeros[0],ones[0]);
pscholtens 4:27a2eaee71ac 139 }
pscholtens 4:27a2eaee71ac 140 for (unsigned int i = 1; i < DEPTH-1; i++) {
pscholtens 1:2551859fbc25 141 if ( zeros[i]+ones[i] != 0 ) {
pscholtens 4:27a2eaee71ac 142 pc.printf(" %8i %8i %8i %8i\n",i,zeros[i],ones[i],assign[i]);
pscholtens 1:2551859fbc25 143 }
pscholtens 1:2551859fbc25 144 }
pscholtens 3:8d13bf073e92 145 if ( zeros[DEPTH-1]+ones[DEPTH-1] != 0 ) {
pscholtens 4:27a2eaee71ac 146 pc.printf("Overflow %8i %8i\n",zeros[DEPTH-1],ones[DEPTH-1]);
pscholtens 3:8d13bf073e92 147 }
pscholtens 3:8d13bf073e92 148
pscholtens 1:2551859fbc25 149 }
pscholtens 1:2551859fbc25 150
pscholtens 6:a5fc4e2ff34b 151 /* Will only be called if measurement time exceeds preset watch dog timer. */
pscholtens 6:a5fc4e2ff34b 152 void at_time_out() {
pscholtens 6:a5fc4e2ff34b 153 pc.printf("Input clipped to level %i, no bitstream present.\n", (int) bitstream);
pscholtens 6:a5fc4e2ff34b 154 timeout.attach(&at_time_out, WATCH_DOG_TIME);
pscholtens 6:a5fc4e2ff34b 155 }
pscholtens 6:a5fc4e2ff34b 156
pscholtens 1:2551859fbc25 157 /* Function which fill the histogram */
pscholtens 1:2551859fbc25 158 void fill_histogram(unsigned int num_unsync_samples) {
pscholtens 1:2551859fbc25 159 unsigned int count = 0;
pscholtens 1:2551859fbc25 160 unsigned int run_length = 0;
pscholtens 2:5e37831540c7 161 bool previous_bit = (bool) bitstream;
pscholtens 6:a5fc4e2ff34b 162 /* Switch on watch dog timer */
pscholtens 6:a5fc4e2ff34b 163 timeout.attach(&at_time_out, WATCH_DOG_TIME);
pscholtens 3:8d13bf073e92 164 /* Implements run-in: skip the first sequence as it is only a partial one. */
pscholtens 6:a5fc4e2ff34b 165 while(previous_bit == (bool) bitstream) {
pscholtens 6:a5fc4e2ff34b 166 /* Do nothing, intentionally */;
pscholtens 3:8d13bf073e92 167 };
pscholtens 4:27a2eaee71ac 168 previous_bit = !previous_bit;
pscholtens 3:8d13bf073e92 169 run_length = 0;
pscholtens 6:a5fc4e2ff34b 170 /* Start actual counting here, store in variable run_length (will be clipped to DEPTH) */
pscholtens 1:2551859fbc25 171 while(count < num_unsync_samples) {
pscholtens 6:a5fc4e2ff34b 172 /* Core of the loop */
pscholtens 6:a5fc4e2ff34b 173 while(previous_bit == (bool) bitstream) {
pscholtens 1:2551859fbc25 174 run_length++;
pscholtens 1:2551859fbc25 175 };
pscholtens 6:a5fc4e2ff34b 176 /* Increment counter before clipping to preserve accuracy. */
pscholtens 6:a5fc4e2ff34b 177 count += run_length;
pscholtens 6:a5fc4e2ff34b 178 /* Test if run length exceeds depth of histogram, if so assign clip value. */
pscholtens 6:a5fc4e2ff34b 179 if (run_length < DEPTH-1) {
pscholtens 6:a5fc4e2ff34b 180 run_length = DEPTH-1;
pscholtens 6:a5fc4e2ff34b 181 }
pscholtens 6:a5fc4e2ff34b 182 /* Now write in histogram array of interest */
pscholtens 1:2551859fbc25 183 if (previous_bit) {
pscholtens 1:2551859fbc25 184 ones[run_length]++;
pscholtens 1:2551859fbc25 185 }
pscholtens 1:2551859fbc25 186 else {
pscholtens 1:2551859fbc25 187 zeros[run_length]++;
pscholtens 1:2551859fbc25 188 }
pscholtens 6:a5fc4e2ff34b 189 /* Reset for next run length counting loop */
pscholtens 2:5e37831540c7 190 run_length = 0;
pscholtens 2:5e37831540c7 191 previous_bit = !previous_bit;
pscholtens 1:2551859fbc25 192 }
pscholtens 6:a5fc4e2ff34b 193 /* Switch off watch dog timer */
pscholtens 6:a5fc4e2ff34b 194 timeout.detach();
pscholtens 1:2551859fbc25 195 }
pscholtens 1:2551859fbc25 196
pscholtens 1:2551859fbc25 197 /* Here we count the number of unsynchronized symbols, mimicing previous implementation */
pscholtens 1:2551859fbc25 198 unsigned int get_num_unsync_symbols(int symbol) {
pscholtens 1:2551859fbc25 199 unsigned int sum = 0;
pscholtens 1:2551859fbc25 200 for (unsigned int i = 0; i < DEPTH; i++) {
pscholtens 1:2551859fbc25 201 if (symbol == 0) {
pscholtens 1:2551859fbc25 202 sum += zeros[i];
pscholtens 1:2551859fbc25 203 } else {
pscholtens 1:2551859fbc25 204 sum += ones[i];
pscholtens 1:2551859fbc25 205 }
pscholtens 1:2551859fbc25 206 }
pscholtens 1:2551859fbc25 207 return sum;
pscholtens 1:2551859fbc25 208 }
pscholtens 1:2551859fbc25 209
pscholtens 3:8d13bf073e92 210 /* Calculate the value, using the unsynchronized method */
pscholtens 3:8d13bf073e92 211 unsigned int get_value_unsync_symbols(int symbol) {
pscholtens 3:8d13bf073e92 212 unsigned int sum = 0;
pscholtens 3:8d13bf073e92 213 for (unsigned int i = 0; i < DEPTH; i++) {
pscholtens 3:8d13bf073e92 214 if (symbol == 0) {
pscholtens 3:8d13bf073e92 215 sum += i*zeros[i];
pscholtens 3:8d13bf073e92 216 } else {
pscholtens 3:8d13bf073e92 217 sum += i*ones[i];
pscholtens 3:8d13bf073e92 218 }
pscholtens 3:8d13bf073e92 219 }
pscholtens 3:8d13bf073e92 220 return sum;
pscholtens 3:8d13bf073e92 221 }
pscholtens 3:8d13bf073e92 222
pscholtens 4:27a2eaee71ac 223 /* Calculate the value, using the synchronization algorithm */
pscholtens 4:27a2eaee71ac 224 unsigned int get_value_synced_symbols(int symbol) {
pscholtens 4:27a2eaee71ac 225 bool presence = false;
pscholtens 4:27a2eaee71ac 226 int value = 0;
pscholtens 4:27a2eaee71ac 227 for (unsigned int i = 0; i < DEPTH; i++) {
pscholtens 4:27a2eaee71ac 228 if ( zeros[i]+ones[i] != 0 ) {
pscholtens 4:27a2eaee71ac 229 if (presence) {
pscholtens 5:1c0bfd69719f 230 assign[i] = value;
pscholtens 4:27a2eaee71ac 231 } else {
pscholtens 4:27a2eaee71ac 232 value++;
pscholtens 5:1c0bfd69719f 233 presence = true;
pscholtens 5:1c0bfd69719f 234 assign[i] = value;
pscholtens 4:27a2eaee71ac 235 }
pscholtens 4:27a2eaee71ac 236 } else {
pscholtens 4:27a2eaee71ac 237 presence = false;
pscholtens 4:27a2eaee71ac 238 }
pscholtens 4:27a2eaee71ac 239 }
pscholtens 4:27a2eaee71ac 240 /* Now do the actual summation of symbol values */
pscholtens 4:27a2eaee71ac 241 unsigned int sum = 0;
pscholtens 4:27a2eaee71ac 242 for (unsigned int i = 0; i < DEPTH; i++) {
pscholtens 4:27a2eaee71ac 243 if (symbol == 0) {
pscholtens 4:27a2eaee71ac 244 sum += assign[i]*zeros[i];
pscholtens 4:27a2eaee71ac 245 } else {
pscholtens 4:27a2eaee71ac 246 sum += assign[i]*ones[i];
pscholtens 4:27a2eaee71ac 247 }
pscholtens 4:27a2eaee71ac 248 }
pscholtens 4:27a2eaee71ac 249 return sum;
pscholtens 4:27a2eaee71ac 250 }
pscholtens 4:27a2eaee71ac 251
pscholtens 7:5141bd76b08d 252 /* Calculate the value, using the new synchronization algorithm */
pscholtens 7:5141bd76b08d 253 float get_dutycycle_synced_symbols_new_method() {
pscholtens 7:5141bd76b08d 254 /* 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 255 bool presence = false;
pscholtens 7:5141bd76b08d 256 Recovered *list = NULL;
pscholtens 7:5141bd76b08d 257 Recovered *first = NULL;
pscholtens 7:5141bd76b08d 258 for (signed int i = DEPTH-2; i > -1 ; i--) {
pscholtens 7:5141bd76b08d 259 if ( zeros[i]+ones[i] != 0 ) {
pscholtens 7:5141bd76b08d 260 if (presence) {
pscholtens 7:5141bd76b08d 261 first->index_start = i;
pscholtens 7:5141bd76b08d 262 } else {
pscholtens 7:5141bd76b08d 263 /* Create new Recovered symbol and position it at the beginning of the list of dis(/re)covered symbols */
pscholtens 7:5141bd76b08d 264 first = new Recovered;
pscholtens 7:5141bd76b08d 265 first->next = list;
pscholtens 7:5141bd76b08d 266 first->index_stop = i+1;
pscholtens 7:5141bd76b08d 267 list = first;
pscholtens 7:5141bd76b08d 268 presence = true;
pscholtens 7:5141bd76b08d 269 }
pscholtens 7:5141bd76b08d 270 } else {
pscholtens 7:5141bd76b08d 271 presence = false;
pscholtens 7:5141bd76b08d 272 }
pscholtens 7:5141bd76b08d 273 }
pscholtens 7:5141bd76b08d 274 /* Step two (第二步): for each found area, calculate average values */
pscholtens 7:5141bd76b08d 275 Recovered* index = list;
pscholtens 7:5141bd76b08d 276 while (index != NULL) {
pscholtens 7:5141bd76b08d 277 index->calc_average();
pscholtens 7:5141bd76b08d 278 index = index->next;
pscholtens 7:5141bd76b08d 279 }
pscholtens 7:5141bd76b08d 280 /* 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 281 float oversample = DEPTH;
pscholtens 7:5141bd76b08d 282 Recovered* cmp1 = list;
pscholtens 7:5141bd76b08d 283 Recovered* cmp2 = list->next;
pscholtens 7:5141bd76b08d 284 if (list != NULL) {
pscholtens 7:5141bd76b08d 285 while (cmp2 != NULL) {
pscholtens 7:5141bd76b08d 286 float diff = cmp2->average-cmp1->average;
pscholtens 7:5141bd76b08d 287 if (diff < oversample) {
pscholtens 7:5141bd76b08d 288 oversample = diff;
pscholtens 7:5141bd76b08d 289 }
pscholtens 7:5141bd76b08d 290 cmp1=cmp2;
pscholtens 7:5141bd76b08d 291 cmp2=cmp1->next;
pscholtens 7:5141bd76b08d 292 }
pscholtens 7:5141bd76b08d 293 }
pscholtens 7:5141bd76b08d 294 /* Step four (第四步): Divide the average run length of all found recovered symbol by the found oversample ratio. */
pscholtens 7:5141bd76b08d 295 index = list;
pscholtens 7:5141bd76b08d 296 while (index != NULL) {
pscholtens 7:5141bd76b08d 297 index->average /= oversample;
pscholtens 7:5141bd76b08d 298 index = index->next;
pscholtens 7:5141bd76b08d 299 }
pscholtens 7:5141bd76b08d 300
pscholtens 7:5141bd76b08d 301 /* Step five (第五步): find offset and remove it (Assumption that there are always symbol with run length 1 ) */
pscholtens 7:5141bd76b08d 302 index = list;
pscholtens 7:5141bd76b08d 303 float offset = oversample-index->average;
pscholtens 7:5141bd76b08d 304 while (index != NULL) {
pscholtens 8:38175daee62b 305 index->average += offset;
pscholtens 7:5141bd76b08d 306 index = index->next;
pscholtens 7:5141bd76b08d 307 }
pscholtens 4:27a2eaee71ac 308
pscholtens 7:5141bd76b08d 309 /* Step six (第六步): round to nearest integer and assign value to both arrays */
pscholtens 7:5141bd76b08d 310 index = list;
pscholtens 7:5141bd76b08d 311 while (index != NULL) {
pscholtens 8:38175daee62b 312 index->assigned_val = (unsigned int) (index->average+0.5);
pscholtens 7:5141bd76b08d 313 for (int i = index->index_start; i < index->index_stop; i++ ) {
pscholtens 7:5141bd76b08d 314 assign[i] = index->assigned_val;
pscholtens 7:5141bd76b08d 315 }
pscholtens 7:5141bd76b08d 316 index = index->next;
pscholtens 7:5141bd76b08d 317 }
pscholtens 7:5141bd76b08d 318
pscholtens 7:5141bd76b08d 319 /* Step seven (第七步): Now do the actual summation of symbol values */
pscholtens 7:5141bd76b08d 320 unsigned int sum0 = 0, sum1 = 0;
pscholtens 7:5141bd76b08d 321 for (unsigned int i = 0; i < DEPTH; i++) {
pscholtens 7:5141bd76b08d 322 sum0 += assign[i]*zeros[i];
pscholtens 7:5141bd76b08d 323 sum1 += assign[i]*ones[i];
pscholtens 7:5141bd76b08d 324 }
pscholtens 7:5141bd76b08d 325 /* Step eight (第八步): Delete the recovered symbol object to clear memory. As a destructor is defined
pscholtens 7:5141bd76b08d 326 this will be automatically handled recursively. And of course return the duty cycle */
pscholtens 7:5141bd76b08d 327 delete list;
pscholtens 7:5141bd76b08d 328 return ((float) sum0)/sum1;
pscholtens 7:5141bd76b08d 329 }
pscholtens 7:5141bd76b08d 330
pscholtens 7:5141bd76b08d 331 /* The main (主程序) routine of the program */
pscholtens 1:2551859fbc25 332
pscholtens 0:dc1b041f713e 333 int main() {
pscholtens 7:5141bd76b08d 334 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 335 sum_of_unsync_symbols, sum_of_synced_symbols;
pscholtens 7:5141bd76b08d 336 float unsync_dutycycle, synced_dutycycle, unsync_voltage, synced_voltage, synced_dutycycle_new, synced_voltage_new;
pscholtens 1:2551859fbc25 337 pc.baud(115200);
pscholtens 9:8136aea421e3 338 pc.printf("Bitstream counter, version 0.1.1, P.C.S. Scholtens, April 24th 2015, Nijmegen, Netherlands.\n");
pscholtens 6:a5fc4e2ff34b 339 pc.printf("Build " __DATE__ " " __TIME__ "\n");
pscholtens 0:dc1b041f713e 340 /*LPC_TIM2->PR = 0x0000002F; / * decimal 47 */
pscholtens 0:dc1b041f713e 341 /*LPC_TIM3->PR = 24;*/
pscholtens 1:2551859fbc25 342 clear_histogram();
pscholtens 0:dc1b041f713e 343 while(1) {
pscholtens 6:a5fc4e2ff34b 344 timer.reset();
pscholtens 0:dc1b041f713e 345 myled = 1;
pscholtens 1:2551859fbc25 346 clear_histogram();
pscholtens 6:a5fc4e2ff34b 347 timer.start();
pscholtens 5:1c0bfd69719f 348 fill_histogram(1e7);
pscholtens 6:a5fc4e2ff34b 349 timer.stop();
pscholtens 4:27a2eaee71ac 350 pc.printf("\n------ Captured Histogram ------\n");
pscholtens 1:2551859fbc25 351 print_histogram();
pscholtens 1:2551859fbc25 352 num_of_zeros = get_num_unsync_symbols(0);
pscholtens 1:2551859fbc25 353 num_of_ones = get_num_unsync_symbols(1);
pscholtens 3:8d13bf073e92 354 value_of_unsync_zeros = get_value_unsync_symbols(0);
pscholtens 3:8d13bf073e92 355 value_of_unsync_ones = get_value_unsync_symbols(1);
pscholtens 7:5141bd76b08d 356 sum_of_unsync_symbols = value_of_unsync_zeros+value_of_unsync_ones;
pscholtens 7:5141bd76b08d 357 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 358 unsync_voltage = (0.5*13*unsync_dutycycle+1)*0.9; /* This is the ADC formula, see analysisSigmaDeltaADC.pdf */
pscholtens 4:27a2eaee71ac 359 value_of_synced_zeros = get_value_synced_symbols(0);
pscholtens 4:27a2eaee71ac 360 value_of_synced_ones = get_value_synced_symbols(1);
pscholtens 7:5141bd76b08d 361 sum_of_synced_symbols = value_of_synced_zeros+value_of_synced_ones;
pscholtens 7:5141bd76b08d 362 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 363 synced_voltage = (0.5*13*synced_dutycycle+1)*0.9; /* This is the ADC formula, see analysisSigmaDeltaADC.pdf */
pscholtens 7:5141bd76b08d 364 synced_dutycycle_new = get_dutycycle_synced_symbols_new_method();
pscholtens 9:8136aea421e3 365 synced_voltage_new = (0.5*13*synced_dutycycle_new+1)*0.9; /* This is the ADC formula, see analysisSigmaDeltaADC.pdf */
pscholtens 4:27a2eaee71ac 366 pc.printf("------ Unsynchronized Results ------\n");
pscholtens 4:27a2eaee71ac 367 pc.printf("Counted Sequences %8i %8i\n", num_of_zeros , num_of_ones);
pscholtens 4:27a2eaee71ac 368 pc.printf("Summed Values %8i %8i\n", value_of_unsync_zeros, value_of_unsync_ones);
pscholtens 4:27a2eaee71ac 369 pc.printf("Duty Cycle %f, equals %f Volt\n", unsync_dutycycle , unsync_voltage);
pscholtens 4:27a2eaee71ac 370 pc.printf("------ Synchronized Results ------\n");
pscholtens 4:27a2eaee71ac 371 pc.printf("Summed Values %8i %8i\n", value_of_synced_zeros, value_of_synced_ones);
pscholtens 4:27a2eaee71ac 372 pc.printf("Duty Cyle %f, equals %f Volt\n", synced_dutycycle , synced_voltage);
pscholtens 7:5141bd76b08d 373 pc.printf("----- Synchronized Results NEW -----\n");
pscholtens 7:5141bd76b08d 374 pc.printf("Duty Cyle %f, equals %f Volt\n", synced_dutycycle_new , synced_voltage_new);
pscholtens 4:27a2eaee71ac 375 pc.printf("------------------------------------\n");
pscholtens 6:a5fc4e2ff34b 376 pc.printf("Measured in %f sec.\n", timer.read());
pscholtens 4:27a2eaee71ac 377 pc.printf("====================================\n");
pscholtens 0:dc1b041f713e 378 myled = 0;
pscholtens 5:1c0bfd69719f 379 wait(0.1);
pscholtens 0:dc1b041f713e 380 }
pscholtens 4:27a2eaee71ac 381 }