xiaozhi/main/boards/common/afsk_demod.cc

#include "afsk_demod.h"
#include <cstring>
#include <algorithm>
#include "esp_log.h"

#ifndef M_PI
#define M_PI 3.14159265358979323846
#endif

namespace audio_wifi_config
{
    static const char *kLogTag = "AUDIO_WIFI_CONFIG";

    void ReceiveWifiCredentialsFromAudio(Application *app,
                                       WifiConfigurationAp *wifi_ap)
    {
        const int kInputSampleRate = 16000;                                    // Input sampling rate
        const float kDownsampleStep = static_cast<float>(kInputSampleRate) / static_cast<float>(kAudioSampleRate); // Downsampling step
        std::vector<int16_t> audio_data;
        AudioSignalProcessor signal_processor(kAudioSampleRate, kMarkFrequency, kSpaceFrequency, kBitRate, kWindowSize);
        AudioDataBuffer data_buffer;

        while (true)
        {
            // 检查Application状态，只有在WiFi配置模式下才处理音频
            if (app->GetDeviceState() != kDeviceStateWifiConfiguring) {
                // 不在WiFi配置状态，休眠100ms后再检查
                vTaskDelay(pdMS_TO_TICKS(100));
                continue;
            }
            
            if (!app->GetAudioService().ReadAudioData(audio_data, 16000, 480)) { // 16kHz, 480 samples corresponds to 30ms data
                // 读取音频失败，短暂延迟后重试
                ESP_LOGI(kLogTag, "Failed to read audio data, retrying.");
                vTaskDelay(pdMS_TO_TICKS(10));
                continue;
            }
            
            // Downsample the audio data
            std::vector<float> downsampled_data;
            size_t last_index = 0;

            if (kDownsampleStep > 1.0f)
            {
                downsampled_data.reserve(audio_data.size() / static_cast<size_t>(kDownsampleStep));
                for (size_t i = 0; i < audio_data.size(); ++i)
                {
                    size_t sample_index = static_cast<size_t>(i / kDownsampleStep);
                    if ((sample_index + 1) > last_index)
                    {
                        downsampled_data.push_back(static_cast<float>(audio_data[i]));
                        last_index = sample_index + 1;
                    }
                }
            }
            else
            {
                downsampled_data.reserve(audio_data.size());
                for (int16_t sample : audio_data)
                {
                    downsampled_data.push_back(static_cast<float>(sample));
                }
            }
            
            // Process audio samples to get probability data
            auto probabilities = signal_processor.ProcessAudioSamples(downsampled_data);
            
            // Feed probability data to the data buffer
            if (data_buffer.ProcessProbabilityData(probabilities, 0.5f))
            {
                // If complete data was received, extract WiFi credentials
                if (data_buffer.decoded_text.has_value())
                {
                    ESP_LOGI(kLogTag, "Received text data: %s", data_buffer.decoded_text->c_str());
                    
                    // Split SSID and password by newline character
                    std::string wifi_ssid, wifi_password;
                    size_t newline_position = data_buffer.decoded_text->find('\n');
                    if (newline_position != std::string::npos)
                    {
                        wifi_ssid = data_buffer.decoded_text->substr(0, newline_position);
                        wifi_password = data_buffer.decoded_text->substr(newline_position + 1);
                        ESP_LOGI(kLogTag, "WiFi SSID: %s, Password: %s", wifi_ssid.c_str(), wifi_password.c_str());
                    }
                    else
                    {
                        ESP_LOGE(kLogTag, "Invalid data format, no newline character found");
                        continue;
                    }
                    
                    if (wifi_ap->ConnectToWifi(wifi_ssid, wifi_password))
                    {
                        wifi_ap->Save(wifi_ssid, wifi_password);  // Save WiFi credentials
                        esp_restart();                            // Restart device to apply new WiFi configuration
                    }
                    else
                    {
                        ESP_LOGE(kLogTag, "Failed to connect to WiFi with received credentials");
                    }
                    data_buffer.decoded_text.reset();  // Clear processed data
                }
            }
            vTaskDelay(pdMS_TO_TICKS(1));  // 1ms delay
        }
    }

    // Default start and end transmission identifiers
    // \x01\x02 = 00000001 00000010
    const std::vector<uint8_t> kDefaultStartTransmissionPattern = {
        0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 1, 0};

    // \x03\x04 = 00000011 00000100
    const std::vector<uint8_t> kDefaultEndTransmissionPattern = {
        0, 0, 0, 0, 0, 0, 1, 1, 0, 0, 0, 0, 0, 1, 0, 0};

    // FrequencyDetector implementation
    FrequencyDetector::FrequencyDetector(float frequency, size_t window_size)
        : frequency_(frequency), window_size_(window_size)
    {
        frequency_bin_ = std::floor(frequency_ * static_cast<float>(window_size_));
        angular_frequency_ = 2.0f * M_PI * frequency_;
        cos_coefficient_ = std::cos(angular_frequency_);
        sin_coefficient_ = std::sin(angular_frequency_);
        filter_coefficient_ = 2.0f * cos_coefficient_;

        // Initialize state buffer
        state_buffer_.push_back(0.0f);
        state_buffer_.push_back(0.0f);
    }

    void FrequencyDetector::Reset()
    {
        state_buffer_.clear();
        state_buffer_.push_back(0.0f);
        state_buffer_.push_back(0.0f);
    }

    void FrequencyDetector::ProcessSample(float sample)
    {
        if (state_buffer_.size() < 2)
        {
            return;
        }

        float s_minus_2 = state_buffer_.front();  // S[-2]
        state_buffer_.pop_front();
        float s_minus_1 = state_buffer_.front();  // S[-1]
        state_buffer_.pop_front();

        float s_current = sample + filter_coefficient_ * s_minus_1 - s_minus_2;

        state_buffer_.push_back(s_minus_1);  // Put S[-1] back
        state_buffer_.push_back(s_current);  // Add new S[0]
    }

    float FrequencyDetector::GetAmplitude() const
    {
        if (state_buffer_.size() < 2)
        {
            return 0.0f;
        }

        float s_minus_1 = state_buffer_[1];                      // S[-1]
        float s_minus_2 = state_buffer_[0];                      // S[-2]
        float real_part = cos_coefficient_ * s_minus_1 - s_minus_2;  // Real part
        float imaginary_part = sin_coefficient_ * s_minus_1;         // Imaginary part

        return std::sqrt(real_part * real_part + imaginary_part * imaginary_part) / 
               (static_cast<float>(window_size_) / 2.0f);
    }

    // AudioSignalProcessor implementation
    AudioSignalProcessor::AudioSignalProcessor(size_t sample_rate, size_t mark_frequency, size_t space_frequency,
                                             size_t bit_rate, size_t window_size)
        : input_buffer_size_(window_size), output_sample_count_(0)
    {
        if (sample_rate % bit_rate != 0)
        {
            // On ESP32 we can continue execution, but log the error
            ESP_LOGW(kLogTag, "Sample rate %zu is not divisible by bit rate %zu", sample_rate, bit_rate);
        }

        float normalized_mark_freq = static_cast<float>(mark_frequency) / static_cast<float>(sample_rate);
        float normalized_space_freq = static_cast<float>(space_frequency) / static_cast<float>(sample_rate);

        mark_detector_ = std::make_unique<FrequencyDetector>(normalized_mark_freq, window_size);
        space_detector_ = std::make_unique<FrequencyDetector>(normalized_space_freq, window_size);

        samples_per_bit_ = sample_rate / bit_rate;  // Number of samples per bit
    }

    std::vector<float> AudioSignalProcessor::ProcessAudioSamples(const std::vector<float> &samples)
    {
        std::vector<float> result;

        for (float sample : samples)
        {
            if (input_buffer_.size() < input_buffer_size_)
            {
                input_buffer_.push_back(sample);  // Just add, don't process yet
            }
            else
            {
                // Input buffer is full, process the data
                input_buffer_.pop_front();   // Remove oldest sample
                input_buffer_.push_back(sample);  // Add new sample
                output_sample_count_++;

                if (output_sample_count_ >= samples_per_bit_)
                {
                    // Process all samples in the window using Goertzel algorithm
                    for (float window_sample : input_buffer_)
                    {
                        mark_detector_->ProcessSample(window_sample);
                        space_detector_->ProcessSample(window_sample);
                    }

                    float mark_amplitude = mark_detector_->GetAmplitude();   // Mark amplitude
                    float space_amplitude = space_detector_->GetAmplitude(); // Space amplitude

                    // Avoid division by zero
                    float mark_probability = mark_amplitude / 
                                           (space_amplitude + mark_amplitude + std::numeric_limits<float>::epsilon());
                    result.push_back(mark_probability);

                    // Reset detector windows
                    mark_detector_->Reset();
                    space_detector_->Reset();
                    output_sample_count_ = 0;  // Reset output counter
                }
            }
        }

        return result;
    }

    // AudioDataBuffer implementation
    AudioDataBuffer::AudioDataBuffer()
        : current_state_(DataReceptionState::kInactive),
          start_of_transmission_(kDefaultStartTransmissionPattern),
          end_of_transmission_(kDefaultEndTransmissionPattern),
          enable_checksum_validation_(true)
    {
        identifier_buffer_size_ = std::max(start_of_transmission_.size(), end_of_transmission_.size());
        max_bit_buffer_size_ = 776;  // Preset bit buffer size, 776 bits = (32 + 1 + 63 + 1) * 8 = 776

        bit_buffer_.reserve(max_bit_buffer_size_);
    }

    AudioDataBuffer::AudioDataBuffer(size_t max_byte_size, const std::vector<uint8_t> &start_identifier,
                                   const std::vector<uint8_t> &end_identifier, bool enable_checksum)
        : current_state_(DataReceptionState::kInactive),
          start_of_transmission_(start_identifier),
          end_of_transmission_(end_identifier),
          enable_checksum_validation_(enable_checksum)
    {
        identifier_buffer_size_ = std::max(start_of_transmission_.size(), end_of_transmission_.size());
        max_bit_buffer_size_ = max_byte_size * 8;  // Bit buffer size in bytes

        bit_buffer_.reserve(max_bit_buffer_size_);
    }

    uint8_t AudioDataBuffer::CalculateChecksum(const std::string &text)
    {
        uint8_t checksum = 0;
        for (char character : text)
        {
            checksum += static_cast<uint8_t>(character);
        }
        return checksum;
    }

    void AudioDataBuffer::ClearBuffers()
    {
        identifier_buffer_.clear();
        bit_buffer_.clear();
    }

    bool AudioDataBuffer::ProcessProbabilityData(const std::vector<float> &probabilities, float threshold)
    {
        for (float probability : probabilities)
        {
            uint8_t bit = (probability > threshold) ? 1 : 0;

            if (identifier_buffer_.size() >= identifier_buffer_size_)
            {
                identifier_buffer_.pop_front();  // Maintain buffer size
            }
            identifier_buffer_.push_back(bit);

            // Process received bit based on state machine
            switch (current_state_)
            {
            case DataReceptionState::kInactive:
                if (identifier_buffer_.size() >= start_of_transmission_.size())
                {
                    current_state_ = DataReceptionState::kWaiting;  // Enter waiting state
                    ESP_LOGI(kLogTag, "Entering Waiting state");
                }
                break;

            case DataReceptionState::kWaiting:
                // Waiting state, possibly waiting for transmission end
                if (identifier_buffer_.size() >= start_of_transmission_.size())
                {
                    std::vector<uint8_t> identifier_snapshot(identifier_buffer_.begin(), identifier_buffer_.end());
                    if (identifier_snapshot == start_of_transmission_)
                    {
                        ClearBuffers();                                // Clear buffers
                        current_state_ = DataReceptionState::kReceiving;  // Enter receiving state
                        ESP_LOGI(kLogTag, "Entering Receiving state");
                    }
                }
                break;

            case DataReceptionState::kReceiving:
                bit_buffer_.push_back(bit);
                if (identifier_buffer_.size() >= end_of_transmission_.size())
                {
                    std::vector<uint8_t> identifier_snapshot(identifier_buffer_.begin(), identifier_buffer_.end());
                    if (identifier_snapshot == end_of_transmission_)
                    {
                        current_state_ = DataReceptionState::kInactive;  // Enter inactive state

                        // Convert bits to bytes
                        std::vector<uint8_t> bytes = ConvertBitsToBytes(bit_buffer_);

                        uint8_t received_checksum = 0;
                        size_t minimum_length = 0;

                        if (enable_checksum_validation_)
                        {
                            // If checksum is required, last byte is checksum
                            minimum_length = 1 + start_of_transmission_.size() / 8;
                            if (bytes.size() >= minimum_length)
                            {
                                received_checksum = bytes[bytes.size() - start_of_transmission_.size() / 8 - 1];
                            }
                        }
                        else
                        {
                            minimum_length = start_of_transmission_.size() / 8;
                        }

                        if (bytes.size() < minimum_length)
                        {
                            ClearBuffers();
                            ESP_LOGW(kLogTag, "Data too short, clearing buffer");
                            return false;  // Data too short, return failure
                        }

                        // Extract text data (remove trailing identifier part)
                        std::vector<uint8_t> text_bytes(
                            bytes.begin(), bytes.begin() + bytes.size() - minimum_length);

                        std::string result(text_bytes.begin(), text_bytes.end());

                        // Validate checksum if required
                        if (enable_checksum_validation_)
                        {
                            uint8_t calculated_checksum = CalculateChecksum(result);
                            if (calculated_checksum != received_checksum)
                            {
                                // Checksum mismatch
                                ESP_LOGW(kLogTag, "Checksum mismatch: expected %d, got %d", 
                                        received_checksum, calculated_checksum);
                                ClearBuffers();
                                return false;
                            }
                        }

                        ClearBuffers();
                        decoded_text = result;
                        return true;  // Return success
                    }
                    else if (bit_buffer_.size() >= max_bit_buffer_size_)
                    {
                        // If not end identifier and bit buffer is full, reset
                        ClearBuffers();
                        ESP_LOGW(kLogTag, "Buffer overflow, clearing buffer");
                        current_state_ = DataReceptionState::kInactive;  // Reset state machine
                    }
                }
                break;
            }
        }

        return false;
    }

    std::vector<uint8_t> AudioDataBuffer::ConvertBitsToBytes(const std::vector<uint8_t> &bits) const
    {
        std::vector<uint8_t> bytes;

        // Ensure number of bits is a multiple of 8
        size_t complete_bytes_count = bits.size() / 8;
        bytes.reserve(complete_bytes_count);

        for (size_t i = 0; i < complete_bytes_count; ++i)
        {
            uint8_t byte_value = 0;
            for (size_t j = 0; j < 8; ++j)
            {
                byte_value |= bits[i * 8 + j] << (7 - j);
            }
            bytes.push_back(byte_value);
        }

        return bytes;
    }
}