preamble detection about advanced-iot-lisat

[Terrasfear]

bool signal_preamble_detector(q15_t* mic_buffer, uint32_t* detection_history)
{
	q15_t match_score;
	uint16_t match_success;
	uint16_t succesfull_detections;
	
	match_score = preamble_match(mic_buffer);
	
	*detection_history = *detection_history >> 1; // shift history
	
	match_success = match_score >= match_threshold;
	*detection_history = *detection_history | (match_success << HISTORY_LENGTH);
	
	succesfull_detections = hamming_weight(*detection_history);
	
	return (succesfull_detections >= DETECTION_THRESHOLD);
}

uint16_t hamming_weight(uint32_t N)
{
    uint16_t result;
    while(N)
    {
        result++;
        N &=N-1;
    }
    return result;
}

[davidzwa]

Done: 3kHz carrier

#94