transceiver/Src/oregon.c

#include "app.h"
#include "nexa.h"
#include "oregon.h"

// Constructor must run resetDecoder()

unsigned char total_bits, bits, flip, state, pos, data[25];

enum { UNKNOWN, T0, T1, T2, T3, OK, DONE };


    boolean nextPulse (unsigned short width) {
        if (state != DONE)
        
            switch (decode(width)) {
                case -1: resetDecoder(); break;
                case 1:  done(); break;
            }
        return isDone();
    }
    
    boolean isDone() {
      return state == DONE;
    }

    const unsigned char* getData (unsigned char& count) {
        count = pos;
        return data; 
    }
    
    void resetDecoder () {
        total_bits = bits = pos = flip = 0;
        state = UNKNOWN;
    }
    
    // add one bit to the packet data buffer
    
    virtual void gotBit (unsigned char value) {
        total_bits++;
        byte *ptr = data + pos;
        *ptr = (*ptr >> 1) | (value << 7);

        if (++bits >= 8) {
            bits = 0;
            if (++pos >= sizeof data) {
                resetDecoder();
                return;
            }
        }
        state = OK;
    }
    
    // store a bit using Manchester encoding
    void manchester (char value) {
        flip ^= value; // manchester code, long pulse flips the bit
        gotBit(flip);
    }
    
    // move bits to the front so that all the bits are aligned to the end
    void alignTail (byte max =0) {
        // align bits
        if (bits != 0) {
            data[pos] >>= 8 - bits;
            for (byte i = 0; i < pos; ++i)
                data[i] = (data[i] >> bits) | (data[i+1] << (8 - bits));
            bits = 0;
        }
        // optionally shift bytes down if there are too many of 'em
        if (max > 0 && pos > max) {
            byte n = pos - max;
            pos = max;
            for (byte i = 0; i < pos; ++i)
                data[i] = data[i+n];
        }
    }
    
    void reverseBits () {
        for (byte i = 0; i < pos; ++i) {
            byte b = data[i];
            for (byte j = 0; j < 8; ++j) {
                data[i] = (data[i] << 1) | (b & 1);
                b >>= 1;
            }
        }
    }
    
    void reverseNibbles () {
        for (byte i = 0; i < pos; ++i)
            data[i] = (data[i] << 4) | (data[i] >> 4);
    }
    
    void done () {
        while (bits)
            gotBit(0); // padding
        state = DONE;
    }


    
    // add one bit to the packet data buffer
    void gotBit (char value) {
        data[pos] = (data[pos] >> 1) | (value ? 0x80 : 00);
        total_bits++;
        pos = total_bits >> 3;
        if (pos >= sizeof data) {
            resetDecoder();
            return;
        }
        state = OK;
    }
    
    virtual char decode (word width) {
        if (200 <= width && width < 1200) {
            byte w = width >= 700;
            switch (state) {
                case UNKNOWN:
                    if (w == 0)
                        ++flip;
                    else if (32 <= flip) {
                        flip = 1;
                        manchester(1);
                    } else
                        return -1;
                    break;
                case OK:
                    if (w == 0)
                        state = T0;
                    else
                        manchester(1);
                    break;
                case T0:
                    if (w == 0)
                        manchester(0);
                    else
                        return -1;
                    break;
            }
        } else {
            return -1;
        }
        return  total_bits == 80 ? 1: 0;
    }