Adds play/pause by tag support.

device/main/AudioPlayer.cpp

@@ -12,5 +12,10 @@ AudioPlayer::AudioPlayer() {
 }
 
 void AudioPlayer::play(char* uri) {
+    esp_player_music_stop();
     esp_player_sdcard_music_play(uri, 0);
 }
+
+void AudioPlayer::pause() {
+    esp_player_music_pause();
+}

device/main/AudioPlayer.hpp

@@ -6,4 +6,5 @@ class AudioPlayer {
 	public:
 		AudioPlayer();
 		void play(char* uri);
+		void pause();
 };

device/main/RFIDInterface.cpp

@@ -23,17 +23,20 @@ RFIDInterface::RFIDInterface() {
         .mosi_io     = 13,
 		.sck_io      = 23,
         .sda_io      = 18,  
-        .callback    = [](uint8_t* sn) { // serial number is always 5 bytes long
-                ESP_LOGI(TAG, "Tag: %#x %#x %#x %#x %#x",
-                    sn[0], sn[1], sn[2], sn[3], sn[4]
-                );
+        .callback    = [](uint8_t* sn) {
+                if (sn == NULL) {
+                    ESP_LOGI(TAG, "Tag removed");
 
-                sprintf(lastTagId, "%#x_%#x_%#x_%#x_%#x", sn[0], sn[1], sn[2], sn[3], sn[4]);
+                    if (callback) {
+                        callback(NULL);
+                    }
+                } else { // serial number is always 5 bytes long
+                    sprintf(lastTagId, "%#x_%#x_%#x_%#x_%#x", sn[0], sn[1], sn[2], sn[3], sn[4]);
+                    ESP_LOGI(TAG, "tag id: %s", lastTagId);
 
-                ESP_LOGI(TAG, "sprintf tag id: %s", lastTagId);
-
-                if (callback) {
-                    callback(getLastTagId());
+                    if (callback) {
+                        callback(getLastTagId());
+                    }
                 }
             }
 	};

device/main/TagPlayerControl.cpp

@@ -15,6 +15,15 @@ TagPlayerControl::TagPlayerControl(AudioPlayer* player) {
 }
 
 void TagPlayerControl::onTagChanged(char* tagId) {
+	if (tagId == NULL) {
+		// tag has been removed. stop playback
+		audioPlayer->pause();
+	} else {
+		playTag(tagId);
+	}
+}
+
+void TagPlayerControl::playTag(char* tagId) {
 	std::string filePath = "/sdcard/internal/";
 	filePath.append(tagId);
 

device/main/TagPlayerControl.hpp

@@ -7,5 +7,9 @@ class TagPlayerControl {
 
 	public:
 		TagPlayerControl(AudioPlayer* player);
+
 		void onTagChanged(char* tagId);
+	
+	private:
+		void playTag(char* tagId);
 };