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https://github.com/SatDump/SatDump
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122 lines
No EOL
3.3 KiB
C++
122 lines
No EOL
3.3 KiB
C++
#include "noaa_deframer.h"
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#define ST_IDLE 0
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#define ST_SYNCED 1
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#define HRPT_SYNC1 0x0284
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#define HRPT_SYNC2 0x016F
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#define HRPT_SYNC3 0x035C
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#define HRPT_SYNC4 0x019D
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#define HRPT_SYNC5 0x020F
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#define HRPT_SYNC6 0x0095
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#define HRPT_MINOR_FRAME_SYNC 0x0A116FD719D83C95LL
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#define HRPT_SYNC_WORDS 6
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#define HRPT_MINOR_FRAME_WORDS 11090
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#define HRPT_BITS_PER_WORD 10
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namespace noaa
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{
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template <typename T>
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inline bool getBit(T &data, int &bit)
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{
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return (data >> bit) & 1;
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}
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// Compare 2 32-bits values bit per bit
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int checkSyncMarker(uint64_t marker, uint64_t totest)
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{
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int errors = 0;
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for (int i = 59; i >= 0; i--)
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{
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bool markerBit, testBit;
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markerBit = getBit<uint64_t>(marker, i);
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testBit = getBit<uint64_t>(totest, i);
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if (markerBit != testBit)
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errors++;
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}
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return errors;
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}
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void NOAADeframer::enter_idle()
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{
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d_state = ST_IDLE;
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}
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void NOAADeframer::enter_synced()
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{
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d_state = ST_SYNCED;
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d_bit_count = HRPT_BITS_PER_WORD;
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d_word_count = HRPT_MINOR_FRAME_WORDS - HRPT_SYNC_WORDS;
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d_word = 0;
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}
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NOAADeframer::NOAADeframer(int thresold)
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{
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d_thresold = thresold;
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d_mid_bit = true;
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d_last_bit = 0;
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enter_idle();
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};
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std::vector<uint16_t> NOAADeframer::work(uint8_t *input, int length)
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{
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std::vector<uint16_t> out;
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int i = 0;
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while (i < length)
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{
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char bit = input[i++];
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char diff = bit ^ d_last_bit;
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d_last_bit = bit;
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// Wait for transition if not synced, otherwise, alternate bits
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if (d_mid_bit && (diff | (d_state == ST_SYNCED)))
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{
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switch (d_state)
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{
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case ST_IDLE:
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d_shifter = (d_shifter << 1) | bit; // MSB transmitted first
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//if ((d_shifter & 0x0FFFFFFFFFFFFFFFLL) == HRPT_MINOR_FRAME_SYNC)
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if (checkSyncMarker(d_shifter & 0x0FFFFFFFFFFFFFFFLL, HRPT_MINOR_FRAME_SYNC) <= d_thresold)
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{
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out.push_back(HRPT_SYNC1);
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out.push_back(HRPT_SYNC2);
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out.push_back(HRPT_SYNC3);
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out.push_back(HRPT_SYNC4);
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out.push_back(HRPT_SYNC5);
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out.push_back(HRPT_SYNC6);
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enter_synced();
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}
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break;
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case ST_SYNCED:
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d_word = (d_word << 1) | bit; // MSB transmitted first
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if (--d_bit_count == 0)
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{
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out.push_back(d_word);
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d_word = 0;
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d_bit_count = HRPT_BITS_PER_WORD;
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if (--d_word_count == 0)
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{
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enter_idle();
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}
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}
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break;
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default:
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break;
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}
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d_mid_bit = false;
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}
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else
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{
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d_mid_bit = true;
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}
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}
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return out;
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}
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} // namespace noaa
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