diff --git a/build_version.sh b/build_version.sh
index 807fff1..c1fcaf1 100755
--- a/build_version.sh
+++ b/build_version.sh
@@ -1,2 +1,2 @@
 #!/bin/bash
-echo -n "-DVERSION=\\\"`git describe --tags --dirty`\\\""
+echo -n "-DVERSION=\\\"`git describe --tags --dirty`-`date +%Y%m%d-%H%M%S`\\\""
diff --git a/include/player.h b/include/player.h
index c1b72f0..a6a9dae 100644
--- a/include/player.h
+++ b/include/player.h
@@ -31,6 +31,11 @@
 #define SM_ADPCM 0x1000
 #define SS_DO_NOT_JUMP 0x8000
 
+struct ID_to_Folder_Map {
+	const char* id;
+	const char* folder;
+};
+
 class Player {
 private:
 	enum state { uninitialized, idle, playing, stopping,
@@ -70,6 +75,8 @@ private:
 	void _patch_adpcm();
 	void _speaker_off();
 	void _speaker_on();
+	void _fill_id_to_folder_map();
+	String _foldername_for_id(String id);
 
 	SPISettings _spi_settings_slow = SPISettings(250000, MSBFIRST, SPI_MODE0);
 	SPISettings _spi_settings_fast = SPISettings(4000000, MSBFIRST, SPI_MODE0);
@@ -89,6 +96,7 @@ private:
 	uint32_t _skip_to;
 	SPIMaster* _spi;
 	unsigned long _stopped_at;
+	std::list<ID_to_Folder_Map> _id_to_folder_map;
 public:
 	Player(SPIMaster* s);
 	void vol_up();
@@ -97,6 +105,7 @@ public:
 	void track_prev();
 	bool is_playing();
 
+	bool play_id(String id);
 	bool play_album(String album);
 	void play_random_album();
 	bool play_song(String album, uint8_t song_index, uint32_t offset=0);
diff --git a/src/controller.cpp b/src/controller.cpp
index 418c9ca..d156090 100644
--- a/src/controller.cpp
+++ b/src/controller.cpp
@@ -64,9 +64,14 @@ void Controller::_check_rfid() {
 		if (uid > 0) {
 			_mqtt_client->publish_rfid_uid(uid);
 			_no_rfid_card_count = 0;
-			INFO("New RFID card uid: %08x\n", uid);
-			String s_uid = String(uid, HEX);
-			_player->play_album(s_uid);
+			String temp = String(uid, HEX);
+			String s_uid = "";
+			for (int i=0; i<(8-s_uid.length()); i++) {
+				s_uid.concat("0");
+			}
+			s_uid.concat(temp);
+			INFO("New RFID card uid: %s\n", s_uid.c_str());
+			_player->play_id(s_uid);
 		} else {
 			if (_no_rfid_card_count >= 1) {
 				INFO("No more RFID card.\n");
@@ -105,7 +110,7 @@ void Controller::_execute_serial_command(String cmd) {
 	} else if (cmd.equals("play")) {
 		_player->play_random_album();
 	} else if (cmd.startsWith("play ")) {
-		_player->play_album(cmd.substring(5));
+		_player->play_id(cmd.substring(5));
 	} else if (cmd.startsWith("sys ")) {
 		_player->play_system_sound(cmd.substring(4));
 	} else if (cmd.equals("stop")) {
diff --git a/src/player.cpp b/src/player.cpp
index 93921a7..ebbaccf 100644
--- a/src/player.cpp
+++ b/src/player.cpp
@@ -14,6 +14,8 @@ Player::Player(SPIMaster* s) {
 	_speaker_off();
 	_spi->disable();
 	PIN_VS1053_DREQ_SETUP();
+	
+	_fill_id_to_folder_map();
 
 	_init();
 }
@@ -400,6 +402,47 @@ std::list<String> Player::_files_in_dir(String path) {
 	return result;
 }
 
+void Player::_fill_id_to_folder_map() {
+	DEBUG("_fill_id_to_folder_map() running...");
+	_spi->select_sd();
+	File root = SD.open("/");
+	File entry;
+	while (entry = root.openNextFile()) {
+		String foldername = entry.name();
+		TRACE("Looking at %s...\n", foldername.c_str());
+		if (!entry.isDirectory() || foldername.startsWith("/.")) continue;
+		if (!SD.exists(foldername + "/id.txt")) {
+			TRACE("Folder %s does not contain id.txt -> ignoring\n", foldername.c_str());
+			continue;
+		}
+		TRACE("Reading contents of %s...\n", (foldername + "/id.txt").c_str());
+		File f = SD.open(foldername + "/id.txt");
+		String buffer = "";
+		while (f.available()) {
+			char c = f.read();
+			if (c=='\n' || c=='\r') {
+				if (buffer.length() > 0) {
+					ID_to_Folder_Map m = {buffer.c_str(), foldername.c_str()};
+					DEBUG("Adding mapping '%s'=>'%s'\n", m.id, m.folder);
+					_id_to_folder_map.push_back(m);
+					buffer = "";
+				}
+			}
+		}
+		f.close();
+		
+		if (buffer.length() > 0) {
+			ID_to_Folder_Map m = {buffer.c_str(), foldername.c_str()};
+			DEBUG("Adding mapping '%s'=>'%s'\n", m.id, m.folder);
+			_id_to_folder_map.push_back(m);
+		}
+		entry.close();
+	}
+	root.close();
+	DEBUG("fill_id_to_folder_map done.\n");
+	_spi->select_sd(false);
+}
+
 String Player::_random_album() {
 	std::list<String> albums = ls("/", false, true, false);
 	uint8_t rnd = random(albums.size());
@@ -412,9 +455,27 @@ void Player::play_random_album() {
 	play_album(_random_album());
 }
 
+bool Player::play_id(String id) {
+	String folder = _foldername_for_id(id);
+	if (folder.length()==0) return false;
+	return play_album(folder);
+}
+
+String Player::_foldername_for_id(String id) {
+	DEBUG("Searching for id %s...\n", id.c_str());
+	for(std::list<ID_to_Folder_Map>::iterator it=_id_to_folder_map.begin(); it!=_id_to_folder_map.end(); it++) {
+		if (id.equals((*it).id)) {
+			DEBUG("Found folder '%s' for id %s.\n", (*it).folder, id.c_str());
+			return (*it).folder;
+		}
+	}
+	DEBUG("No folder found for id %s.\n", id.c_str());
+	return "";
+}
+
 bool Player::play_album(String album) {
 	album_state s = _last_tracks[album.c_str()];
-	DEBUG("Last index for album %s was %d,%d\n", album.c_str(), s.index, s.position);
+	DEBUG("Last index for album '%s' was %d,%d\n", album.c_str(), s.index, s.position);
 	return play_song(album, s.index, s.position);
 }
 
@@ -422,14 +483,7 @@ bool Player::play_song(String album, uint8_t index, uint32_t skip_to) {
 	if (_state == sleeping || _state == recording) _wakeup();
 	if (_state != idle) return false;
 	DEBUG("Trying to play song at index %d, offset %d of album %s\n", index, skip_to, album.c_str());
-	String path = _find_album_dir(album);
-	if (path.length()==0) {
-		ERROR("Could not find album.\n");
-		return false;
-	} else {
-		INFO("Found album in dir '%s'.\n", path.c_str());
-	}
-	std::list<String> files = _files_in_dir(path);
+	std::list<String> files = _files_in_dir(album);
 	_playing_album_songs = files.size();
 	DEBUG("Found %d songs in album\n", files.size());
 	if (index >= files.size()) {