Stanford Student Space Initiative / Mbed 2 deprecated Optical3cmRX

SSI OpComms 3CM Board RX

Dependencies:   mbed

Fork of Optical3cmRX by Thomas Teisberg

main.cpp@7:41b22e5a1d8d, 2015-11-16 (annotated)

Committer:
bhz
Date:
Mon Nov 16 00:08:19 2015 +0000
Revision:
7:41b22e5a1d8d
Parent:
6:6c996fb7a742
Child:
8:20d405a03cb9
Implemented basic checksum

Who changed what in which revision?

UserRevisionLine numberNew contents of line
mbed_official 0:879aa9d0247b 1 #include "mbed.h"
bhz 6:6c996fb7a742 2 #include <sstream>
bhz 5:fc3ce1c5db88 3 #include <string>
bhz 6:6c996fb7a742 4 #include <queue>
bhz 5:fc3ce1c5db88 5 using namespace std;
tteisberg 1:b446f401a861 6
tteisberg 1:b446f401a861 7 AnalogIn rx(p20);
tteisberg 1:b446f401a861 8
mbed_official 0:879aa9d0247b 9 Serial pc(USBTX, USBRX); // tx, rx
tteisberg 1:b446f401a861 10
bhz 5:fc3ce1c5db88 11 // e.g. PPM_BITS = 2 --> 4-PPM; PPM_BITS = 3 --> 8-PPM, etc.
bhz 4:037345932888 12 static const int PPM_BITS = 2;
bhz 4:037345932888 13 static const int N_PPM = 1 << PPM_BITS;
bhz 6:6c996fb7a742 14 static const int EOM = N_PPM;
bhz 6:6c996fb7a742 15 static int PULSE_TIME; // microseconds
bhz 6:6c996fb7a742 16 static int SAMPLE_RATE; // must be a divisor of PULSE_TIME;
bhz 6:6c996fb7a742 17 static int SAMPLE_GAP;
bhz 6:6c996fb7a742 18 static int HALF_SAMPLE;
bhz 6:6c996fb7a742 19 static double THRESH; // threshold for 1 vs 0. Must adjust in the field by testing.
bhz 2:eb447fcd8284 20
bhz 6:6c996fb7a742 21 queue<int> sbuf;
bhz 2:eb447fcd8284 22 bool sample_lock = false;
bhz 2:eb447fcd8284 23 int offCount, onCount;
tteisberg 1:b446f401a861 24
bhz 5:fc3ce1c5db88 25 string getLine(string prompt)
bhz 5:fc3ce1c5db88 26 {
bhz 5:fc3ce1c5db88 27 while(pc.readable()) pc.getc();
bhz 5:fc3ce1c5db88 28 pc.printf(prompt.c_str());
bhz 5:fc3ce1c5db88 29 string out;
bhz 5:fc3ce1c5db88 30 char c;
bhz 5:fc3ce1c5db88 31 while((c = pc.getc()) != '\n')
bhz 5:fc3ce1c5db88 32 {
bhz 5:fc3ce1c5db88 33 out += c;
bhz 5:fc3ce1c5db88 34 }
bhz 5:fc3ce1c5db88 35 pc.printf((out + "\r\n").c_str());
bhz 5:fc3ce1c5db88 36 return out;
bhz 5:fc3ce1c5db88 37 }
bhz 5:fc3ce1c5db88 38
bhz 5:fc3ce1c5db88 39 double getNumber(string prompt, double def)
bhz 5:fc3ce1c5db88 40 {
bhz 5:fc3ce1c5db88 41 string s = getLine(prompt);
bhz 5:fc3ce1c5db88 42 istringstream ints(s);
bhz 5:fc3ce1c5db88 43 double out;
bhz 5:fc3ce1c5db88 44 if(!(ints >> out)) out = def;
bhz 5:fc3ce1c5db88 45 return out;
bhz 5:fc3ce1c5db88 46 }
bhz 5:fc3ce1c5db88 47
bhz 5:fc3ce1c5db88 48 void set_constants()
bhz 5:fc3ce1c5db88 49 {
bhz 5:fc3ce1c5db88 50 PULSE_TIME = (int) getNumber("Input pulse time (us; blank for 1000): ", 1000);
bhz 5:fc3ce1c5db88 51 SAMPLE_RATE = (int) getNumber("Input sample rate (blank for 10): ", 10);
bhz 5:fc3ce1c5db88 52 THRESH = getNumber("Input threshold (blank for 0.005): ", 0.005);
bhz 6:6c996fb7a742 53 pc.printf("Parameters: PULSE_TIME=%d, SAMPLE_RATE=%d, THRESH=%f\r\n", PULSE_TIME, SAMPLE_RATE, THRESH);
bhz 5:fc3ce1c5db88 54 SAMPLE_GAP = PULSE_TIME / SAMPLE_RATE;
bhz 5:fc3ce1c5db88 55 HALF_SAMPLE = SAMPLE_RATE / 2;
bhz 5:fc3ce1c5db88 56 }
bhz 5:fc3ce1c5db88 57
bhz 6:6c996fb7a742 58 void printDecodeBuf()
bhz 6:6c996fb7a742 59 {
bhz 6:6c996fb7a742 60 char cur = 0;
bhz 6:6c996fb7a742 61 int k = 0;
bhz 6:6c996fb7a742 62 string data;
bhz 7:41b22e5a1d8d 63 //pc.printf("\r\nsbuf: ");
bhz 6:6c996fb7a742 64 while(!sbuf.empty())
bhz 6:6c996fb7a742 65 {
bhz 6:6c996fb7a742 66 int c = sbuf.front();
bhz 6:6c996fb7a742 67 sbuf.pop();
bhz 6:6c996fb7a742 68 if(c == EOM) break;
bhz 7:41b22e5a1d8d 69 //pc.printf("%d ", c);
bhz 6:6c996fb7a742 70 if(sbuf.empty())
bhz 6:6c996fb7a742 71 {
bhz 6:6c996fb7a742 72 pc.printf("\r\nWarning: reached end of buffer\r\n");
bhz 6:6c996fb7a742 73 }
bhz 6:6c996fb7a742 74 for(int j = 0; j < PPM_BITS; j++)
bhz 6:6c996fb7a742 75 {
bhz 6:6c996fb7a742 76 // do some bit hacking to put the bit into the proper character in the output array
bhz 6:6c996fb7a742 77 bool bit = (c >> (PPM_BITS - j - 1)) & 1;
bhz 6:6c996fb7a742 78 cur |= bit << (7 - k%8);
bhz 6:6c996fb7a742 79 k++;
bhz 6:6c996fb7a742 80 if(k%8 == 0)
bhz 6:6c996fb7a742 81 {
bhz 6:6c996fb7a742 82 data += cur;
bhz 6:6c996fb7a742 83 cur = 0;
bhz 6:6c996fb7a742 84 }
bhz 6:6c996fb7a742 85 }
bhz 6:6c996fb7a742 86 }
bhz 7:41b22e5a1d8d 87 int rcv_checksum = data[data.size()-1];
bhz 7:41b22e5a1d8d 88 data.erase(data.size()-1, data.size());
bhz 7:41b22e5a1d8d 89 pc.printf("Received: \"");
bhz 6:6c996fb7a742 90 pc.printf(data.c_str());
bhz 6:6c996fb7a742 91 pc.printf("\"\r\n");
bhz 7:41b22e5a1d8d 92
bhz 7:41b22e5a1d8d 93 int checksum = 0;
bhz 7:41b22e5a1d8d 94 for(int i = 0; i < data.size(); i++) checksum ^= data[i];
bhz 7:41b22e5a1d8d 95
bhz 7:41b22e5a1d8d 96 pc.printf("Received: %d | Computed: %d\r\n", rcv_checksum, checksum);
bhz 6:6c996fb7a742 97 }
bhz 6:6c996fb7a742 98
tteisberg 1:b446f401a861 99
bhz 5:fc3ce1c5db88 100 // Samples once, and writes to the buffer if necessary.
bhz 2:eb447fcd8284 101 void sample()
bhz 2:eb447fcd8284 102 {
bhz 2:eb447fcd8284 103 if(sample_lock) pc.printf("\r\nWarning: Sampling too fast\r\n");
bhz 2:eb447fcd8284 104 sample_lock = true;
bhz 2:eb447fcd8284 105 float v = rx.read();
bhz 3:1235cbe67ec9 106 if(v < THRESH){
bhz 2:eb447fcd8284 107 offCount++;
bhz 3:1235cbe67ec9 108 if(onCount > HALF_SAMPLE)
bhz 3:1235cbe67ec9 109 {
bhz 3:1235cbe67ec9 110 onCount = 0;
bhz 3:1235cbe67ec9 111 }
bhz 2:eb447fcd8284 112 }else{ // Pulse
bhz 3:1235cbe67ec9 113 if(offCount > HALF_SAMPLE)
bhz 2:eb447fcd8284 114 {
bhz 3:1235cbe67ec9 115 int offPulses = (offCount + HALF_SAMPLE) / SAMPLE_RATE - 1;
bhz 6:6c996fb7a742 116 if(offPulses < N_PPM)
bhz 2:eb447fcd8284 117 {
bhz 7:41b22e5a1d8d 118 pc.printf("%d ", offPulses);
bhz 6:6c996fb7a742 119 sbuf.push(offPulses);
bhz 2:eb447fcd8284 120 }
bhz 2:eb447fcd8284 121 offCount = 0;
bhz 2:eb447fcd8284 122 }
bhz 2:eb447fcd8284 123 onCount++;
tteisberg 1:b446f401a861 124 }
bhz 2:eb447fcd8284 125 sample_lock = false;
tteisberg 1:b446f401a861 126 }
tteisberg 1:b446f401a861 127
tteisberg 1:b446f401a861 128 int main()
tteisberg 1:b446f401a861 129 {
bhz 2:eb447fcd8284 130 pc.printf("3 CM Link Board - Recieve\r\n");
bhz 5:fc3ce1c5db88 131 //*
tteisberg 1:b446f401a861 132 bool calib = true;
tteisberg 1:b446f401a861 133 if(calib){
tteisberg 1:b446f401a861 134 while(true){
bhz 5:fc3ce1c5db88 135 // Just prints raw values until the user gives some input
bhz 2:eb447fcd8284 136 pc.printf("%f\r\r\n", rx.read());
tteisberg 1:b446f401a861 137 wait_ms(100);
bhz 5:fc3ce1c5db88 138 if(pc.readable()) {
bhz 5:fc3ce1c5db88 139 break;
bhz 5:fc3ce1c5db88 140 }
tteisberg 1:b446f401a861 141 }
tteisberg 1:b446f401a861 142 }
bhz 5:fc3ce1c5db88 143 set_constants();
bhz 5:fc3ce1c5db88 144 pc.printf("Ready! \r\n");
bhz 2:eb447fcd8284 145 offCount = 0;
tteisberg 1:b446f401a861 146 offCount = 0;
bhz 4:037345932888 147 //*/
bhz 2:eb447fcd8284 148 Ticker sampler;
bhz 2:eb447fcd8284 149 sampler.attach_us(&sample, SAMPLE_GAP);
bhz 2:eb447fcd8284 150
tteisberg 1:b446f401a861 151 while(true){
bhz 7:41b22e5a1d8d 152 if((offCount + HALF_SAMPLE) / SAMPLE_RATE > N_PPM && !sbuf.empty()){ // synchronize
bhz 6:6c996fb7a742 153 pc.printf("\r\n");
bhz 6:6c996fb7a742 154 sbuf.push(EOM);
bhz 6:6c996fb7a742 155 printDecodeBuf();
tteisberg 1:b446f401a861 156 }
bhz 4:037345932888 157 wait_us(PULSE_TIME);
mbed_official 0:879aa9d0247b 158 }
mbed_official 0:879aa9d0247b 159 }