v1.7.7: 支持 EC801E 模组，增加 xmini-c3-v3, xmini-c3-4g (#930)

main/audio_codecs/audio_codec.cc

@@ -34,8 +34,13 @@ void AudioCodec::Start() {
         output_volume_ = 10;
     }
 
-    ESP_ERROR_CHECK(i2s_channel_enable(tx_handle_));
-    ESP_ERROR_CHECK(i2s_channel_enable(rx_handle_));
+    if (tx_handle_ != nullptr) {
+        ESP_ERROR_CHECK(i2s_channel_enable(tx_handle_));
+    }
+
+    if (rx_handle_ != nullptr) {
+        ESP_ERROR_CHECK(i2s_channel_enable(rx_handle_));
+    }
 
     EnableInput(true);
     EnableOutput(true);

main/audio_codecs/dummy_audio_codec.cc

@@ -0,0 +1,20 @@
+#include "dummy_audio_codec.h"
+
+DummyAudioCodec::DummyAudioCodec(int input_sample_rate, int output_sample_rate) {
+    duplex_ = true;
+    input_reference_ = false;
+    input_channels_ = 1;
+    input_sample_rate_ = input_sample_rate;
+    output_sample_rate_ = output_sample_rate;
+}
+
+DummyAudioCodec::~DummyAudioCodec() {
+}
+
+int DummyAudioCodec::Read(int16_t* dest, int samples) {
+    return 0;
+}
+
+int DummyAudioCodec::Write(const int16_t* data, int samples) {
+    return 0;
+}

main/audio_codecs/dummy_audio_codec.h

@@ -0,0 +1,16 @@
+#ifndef _DUMMY_AUDIO_CODEC_H
+#define _DUMMY_AUDIO_CODEC_H
+
+#include "audio_codec.h"
+
+class DummyAudioCodec : public AudioCodec {
+private:
+    virtual int Read(int16_t* dest, int samples) override;
+    virtual int Write(const int16_t* data, int samples) override;
+
+public:
+    DummyAudioCodec(int input_sample_rate, int output_sample_rate);
+    virtual ~DummyAudioCodec();
+};
+
+#endif // _DUMMY_AUDIO_CODEC_H