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POCSAG State machine fix (#1410)
* Reset color for well-formed message fragments * better colors * Fix POGSAG decode state machine * Invert is_message to make more clear * Use new escape string constants * Run ECC twice, better diagnostics * center status icon --------- Co-authored-by: kallanreed <kallanreed@noreply.github.com>
This commit is contained in:
Kyle Reed
GitHub
parent
cf25d85d51
commit
933920edfd
4 changed files with 200 additions and 138 deletions
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@ -226,14 +226,17 @@ void pocsag_encode(const MessageType type, BCHCode& BCH_code, const uint32_t fun
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}
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// -------------------------------------------------------------------------------
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// Get the number of bits that differ between the two values.
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// -------------------------------------------------------------------------------
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inline int bitsDiff(unsigned long left, unsigned long right) {
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inline uint8_t bitsDiff(unsigned long left, unsigned long right) {
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unsigned long xord = left ^ right;
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int count = 0;
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uint8_t count = 0;
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for (int i = 0; i < 32; i++) {
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if ((xord & 0x01) != 0) ++count;
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if ((xord & 0x01) == 1) ++count;
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xord = xord >> 1;
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}
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return (count);
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}
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@ -310,7 +313,7 @@ void setupecc() {
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// -------------------------------------------------------------------------------
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// -------------------------------------------------------------------------------
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inline int errorCorrection(uint32_t* val) {
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inline int errorCorrection(uint32_t& val) {
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// Set up the tables the first time
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if (eccSetup == 0) {
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setupecc();
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@ -327,7 +330,7 @@ inline int errorCorrection(uint32_t* val) {
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// for (i=0; i<=20; i++)
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ecc = 0;
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for (i = 31; i >= 11; --i) {
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if ((*val & (1 << i))) {
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if (val & (1 << i)) {
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ecc = ecc ^ ecs[31 - i];
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pari = pari ^ 0x01;
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}
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@ -337,7 +340,7 @@ inline int errorCorrection(uint32_t* val) {
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acc = 0;
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for (i = 10; i >= 1; --i) {
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acc = acc << 1;
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if ((*val & (1 << i))) {
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if (val & (1 << i)) {
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acc = acc ^ 0x01;
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}
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}
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@ -355,12 +358,12 @@ inline int errorCorrection(uint32_t* val) {
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b2 = b2 & 0x1f;
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if (b2 != 0x1f) {
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*val ^= 0x01 << (31 - b2);
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val ^= 0x01 << (31 - b2);
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ecc = ecc ^ ecs[b2];
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}
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if (b1 != 0x1f) {
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*val ^= 0x01 << (31 - b1);
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val ^= 0x01 << (31 - b1);
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ecc = ecc ^ ecs[b1];
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}
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@ -377,78 +380,86 @@ inline int errorCorrection(uint32_t* val) {
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return errl;
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}
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void pocsag_decode_batch(const POCSAGPacket& batch, POCSAGState* const state) {
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int errors = 0;
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uint32_t codeword;
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char ascii_char;
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std::string output_text = "";
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bool pocsag_decode_batch(const POCSAGPacket& batch, POCSAGState& state) {
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constexpr uint8_t codeword_max = 16;
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state.output.clear();
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state->out_type = EMPTY;
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while (state.codeword_index < codeword_max) {
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auto codeword = batch[state.codeword_index];
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bool is_address = (codeword & 0x80000000U) == 0;
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// For each codeword...
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for (size_t i = 0; i < 16; i++) {
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codeword = batch[i];
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// Error correct twice. First time to fix any errors it can,
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// second time to count number of errors that couldn't be fixed.
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errorCorrection(codeword);
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auto error_count = errorCorrection(codeword);
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errorCorrection(&codeword);
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errors = errorCorrection(&codeword);
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switch (state.mode) {
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case STATE_CLEAR:
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if (is_address && codeword != POCSAG_IDLEWORD) {
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state.function = (codeword >> 11) & 3;
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state.address = (codeword >> 10) & 0x1FFFF8U; // 18 MSBs are transmitted
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state.mode = STATE_HAVE_ADDRESS;
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state.out_type = ADDRESS;
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state.errors = error_count;
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if (!(codeword & 0x80000000U)) {
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// Address codeword
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if (state->mode == STATE_CLEAR) {
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// if (codeword != POCSAG_IDLEWORD) {
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if (!(bitsDiff(codeword, POCSAG_IDLEWORD) < 1)) {
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state->function = (codeword >> 11) & 3;
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state->address = (codeword >> 10) & 0x1FFFF8U; // 18 MSBs are transmitted
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state->mode = STATE_HAVE_ADDRESS;
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state->out_type = ADDRESS;
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state->errors = errors;
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state->ascii_idx = 0;
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state->ascii_data = 0;
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state.ascii_idx = 0;
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state.ascii_data = 0;
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} else if (codeword == POCSAG_IDLEWORD) {
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state.out_type = IDLE;
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}
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} else {
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state->mode = STATE_CLEAR; // New address = new message
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}
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} else {
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state->errors += errors;
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// Message codeword
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if (state->mode == STATE_HAVE_ADDRESS) {
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// First message codeword: complete address
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state->address |= (i >> 1); // Add in the 3 LSBs (frame #)
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state->mode = STATE_GETTING_MSG;
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}
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break;
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state->out_type = MESSAGE;
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case STATE_HAVE_ADDRESS:
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if (is_address) {
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// Got another address, return the current state.
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state.mode = STATE_CLEAR;
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return true;
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}
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state->ascii_data |= ((codeword >> 11) & 0xFFFFF); // Get 20 message bits
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state->ascii_idx += 20;
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// First message codeword, complete the address.
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state.address |= (state.codeword_index >> 1); // Add in the 3 LSBs (frame #).
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state.mode = STATE_GETTING_MSG;
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[[fallthrough]];
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// Raw 20 bits to 7 bit reversed ASCII
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while (state->ascii_idx >= 7) {
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state->ascii_idx -= 7;
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ascii_char = ((state->ascii_data) >> (state->ascii_idx)) & 0x7F;
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case STATE_GETTING_MSG:
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if (is_address) {
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// Codeword isn't a message, return the current state.
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state.mode = STATE_CLEAR;
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return true;
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}
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// Bottom's up
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ascii_char = (ascii_char & 0xF0) >> 4 | (ascii_char & 0x0F) << 4; // 01234567 -> 45670123
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ascii_char = (ascii_char & 0xCC) >> 2 | (ascii_char & 0x33) << 2; // 45670123 -> 67452301
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ascii_char = (ascii_char & 0xAA) >> 2 | (ascii_char & 0x55); // 67452301 -> *7654321
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state.out_type = MESSAGE;
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state.errors += error_count;
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state.ascii_data |= (codeword >> 11) & 0xFFFFF; // Get 20 message bits.
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state.ascii_idx += 20;
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// Translate non-printable chars
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if ((ascii_char < 32) || (ascii_char > 126)) {
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// output_text += "[" + to_string_dec_uint(ascii_char) + "]";
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output_text += ".";
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} else
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output_text += ascii_char;
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}
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// Raw 20 bits to 7 bit reversed ASCII.
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// NB: This is processed MSB first, any remaining bits are shifted
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// up so a whole 7 bits are processed with the next codeword.
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while (state.ascii_idx >= 7) {
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state.ascii_idx -= 7;
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char ascii_char = (state.ascii_data >> state.ascii_idx) & 0x7F;
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state->ascii_data <<= 20; // Remaining bits are for next time...
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// Bottom's up (reverse the bits).
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ascii_char = (ascii_char & 0xF0) >> 4 | (ascii_char & 0x0F) << 4; // 01234567 -> 45670123
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ascii_char = (ascii_char & 0xCC) >> 2 | (ascii_char & 0x33) << 2; // 45670123 -> 67452301
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ascii_char = (ascii_char & 0xAA) >> 2 | (ascii_char & 0x55); // 67452301 -> 76543210
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// Translate non-printable chars. TODO: Leave CRLF?
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if (ascii_char < 32 || ascii_char > 126)
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state.output += ".";
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else
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state.output += ascii_char;
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}
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state.ascii_data <<= 20; // Remaining bits are for next iteration...
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break;
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}
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state.codeword_index++;
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}
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state->output = output_text;
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if (state->mode == STATE_HAVE_ADDRESS)
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state->mode = STATE_CLEAR;
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return false;
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}
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} /* namespace pocsag */
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