diff --git a/.travis.yml b/.travis.yml
index 306b838..1071bd9 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -9,23 +9,30 @@ cache:
         - "~/.platformio"
 
 env:
-    - PLATFORMIO_CI_SRC=examples/ChangeUID/ChangeUID.ino
-    - PLATFORMIO_CI_SRC=examples/DumpInfo/DumpInfo.ino
-    - PLATFORMIO_CI_SRC=examples/firmware_check/firmware_check.ino
-    - PLATFORMIO_CI_SRC=examples/FixBrickedUID/FixBrickedUID.ino
-    - PLATFORMIO_CI_SRC=examples/MifareClassicValueBlock/MifareClassicValueBlock.ino
-    - PLATFORMIO_CI_SRC=examples/MinimalInterrupt/MinimalInterrupt.ino
-    - PLATFORMIO_CI_SRC=examples/ReadAndWrite/ReadAndWrite.ino
-    - PLATFORMIO_CI_SRC=examples/ReadUidMultiReader/ReadUidMultiReader.ino
-    - PLATFORMIO_CI_SRC=examples/rfid_default_keys/rfid_default_keys.ino
-    - PLATFORMIO_CI_SRC=examples/rfid_write_personal_data/rfid_write_personal_data.ino
-    - PLATFORMIO_CI_SRC=examples/Ntag216_AUTH/Ntag216_AUTH.ino
-    - PLATFORMIO_CI_SRC=examples/ReadNUID/ReadNUID.ino
-    - PLATFORMIO_CI_SRC=examples/servo_motor/servo_motor.ino
-    - PLATFORMIO_CI_SRC=examples/RFID-Cloner/RFID-Cloner.ino
+    # add examples here and define which boards should be tested (only compile test)
+    - PLATFORMIO_CI_SRC=examples/ChangeUID/ChangeUID.ino TESTBOARD=arduino_avr,arduino_arm,teensy,esp
+    - PLATFORMIO_CI_SRC=examples/DumpInfo/DumpInfo.ino TESTBOARD=arduino_avr,arduino_arm,teensy,esp
+    - PLATFORMIO_CI_SRC=examples/firmware_check/firmware_check.ino TESTBOARD=arduino_avr,arduino_arm,teensy,esp
+    - PLATFORMIO_CI_SRC=examples/FixBrickedUID/FixBrickedUID.ino TESTBOARD=arduino_avr,arduino_arm,teensy,esp
+    - PLATFORMIO_CI_SRC=examples/MifareClassicValueBlock/MifareClassicValueBlock.ino TESTBOARD=arduino_avr,arduino_arm,teensy,esp
+    - PLATFORMIO_CI_SRC=examples/MinimalInterrupt/MinimalInterrupt.ino TESTBOARD=arduino_avr,arduino_arm,teensy,esp
+    - PLATFORMIO_CI_SRC=examples/ReadAndWrite/ReadAndWrite.ino TESTBOARD=arduino_avr,arduino_arm,teensy,esp
+    - PLATFORMIO_CI_SRC=examples/ReadUidMultiReader/ReadUidMultiReader.ino TESTBOARD=arduino_avr,arduino_arm,teensy,esp
+    - PLATFORMIO_CI_SRC=examples/rfid_default_keys/rfid_default_keys.ino TESTBOARD=arduino_avr,arduino_arm,teensy,esp
+    - PLATFORMIO_CI_SRC=examples/rfid_write_personal_data/rfid_write_personal_data.ino TESTBOARD=arduino_avr,arduino_arm,teensy,esp
+    - PLATFORMIO_CI_SRC=examples/Ntag216_AUTH/Ntag216_AUTH.ino TESTBOARD=arduino_avr,arduino_arm,teensy,esp
+    - PLATFORMIO_CI_SRC=examples/ReadNUID/ReadNUID.ino TESTBOARD=arduino_avr,arduino_arm,teensy,esp
+    - PLATFORMIO_CI_SRC=examples/servo_motor/servo_motor.ino TESTBOARD=arduino_avr,teensy
+    - PLATFORMIO_CI_SRC=examples/RFID-Cloner/RFID-Cloner.ino TESTBOARD=arduino_avr,arduino_arm,teensy,esp
 
 install:
     - pip install -U platformio
 
 script:
-    - platformio ci --lib=. --board=uno --board=megaatmega1280 --board=teensy31
+    # short the string comparison
+    - stringContain() { [ -z "${2##*$1*}" ]; }
+    # selectable board tests @Rotzbua
+    - board="arduino_avr";  if stringContain "$board" "$TESTBOARD"; then echo "check board $board"; platformio ci --lib=. --board=uno --board=megaatmega1280; else echo "skip board test of $board"; fi
+    - board="arduino_arm";  if stringContain "$board" "$TESTBOARD"; then echo "check board $board"; platformio ci --lib=. --board=due --board=zero; else echo "skip board test of $board"; fi
+    - board="teensy";  if stringContain "$board" "$TESTBOARD"; then echo "check board $board"; platformio ci --lib=. --board=teensy31; else echo "skip board test of $board"; fi
+    - board="esp";  if stringContain "$board" "$TESTBOARD"; then echo "check board $board"; platformio ci --lib=. --board=d1_mini; else echo "skip board test of $board"; fi
diff --git a/MFRC522.cpp b/MFRC522.cpp
index 1d91670..6979b8e 100644
--- a/MFRC522.cpp
+++ b/MFRC522.cpp
@@ -698,7 +698,7 @@ MFRC522::StatusCode MFRC522::PICC_Select(	Uid *uid,			///< Pointer to Uid struct
 				if (valueOfCollReg & 0x20) { // CollPosNotValid
 					return STATUS_COLLISION; // Without a valid collision position we cannot continue
 				}
-				byte collisionPos = result & 0x1F; // Values 0-31, 0 means bit 32.
+				byte collisionPos = valueOfCollReg & 0x1F; // Values 0-31, 0 means bit 32.
 				if (collisionPos == 0) {
 					collisionPos = 32;
 				}
@@ -1301,23 +1301,11 @@ void MFRC522::PICC_DumpToSerial(Uid *uid	///< Pointer to Uid struct returned fro
 								) {
 	MIFARE_Key key;
 	
-	// UID
-	Serial.print(F("Card UID:"));
-	for (byte i = 0; i < uid->size; i++) {
-		if(uid->uidByte[i] < 0x10)
-			Serial.print(F(" 0"));
-		else
-			Serial.print(F(" "));
-		Serial.print(uid->uidByte[i], HEX);
-	} 
-	Serial.println();
-	
-	// PICC type
-	PICC_Type piccType = PICC_GetType(uid->sak);
-	Serial.print(F("PICC type: "));
-	Serial.println(PICC_GetTypeName(piccType));
+	// Dump UID, SAK and Type
+	PICC_DumpDetailsToSerial(uid);
 	
 	// Dump contents
+	PICC_Type piccType = PICC_GetType(uid->sak);
 	switch (piccType) {
 		case PICC_TYPE_MIFARE_MINI:
 		case PICC_TYPE_MIFARE_1K:
@@ -1350,6 +1338,34 @@ void MFRC522::PICC_DumpToSerial(Uid *uid	///< Pointer to Uid struct returned fro
 	PICC_HaltA(); // Already done if it was a MIFARE Classic PICC.
 } // End PICC_DumpToSerial()
 
+/**
+ * Dumps card info (UID,SAK,Type) about the selected PICC to Serial.
+ */
+void MFRC522::PICC_DumpDetailsToSerial(Uid *uid	///< Pointer to Uid struct returned from a successful PICC_Select().
+									) {
+	// UID
+	Serial.print(F("Card UID:"));
+	for (byte i = 0; i < uid->size; i++) {
+		if(uid->uidByte[i] < 0x10)
+			Serial.print(F(" 0"));
+		else
+			Serial.print(F(" "));
+		Serial.print(uid->uidByte[i], HEX);
+	} 
+	Serial.println();
+	
+	// SAK
+	Serial.print(F("Card SAK: "));
+	if(uid->sak < 0x10)
+		Serial.print(F("0"));
+	Serial.println(uid->sak, HEX);
+	
+	// (suggested) PICC type
+	PICC_Type piccType = PICC_GetType(uid->sak);
+	Serial.print(F("PICC type: "));
+	Serial.println(PICC_GetTypeName(piccType));
+} // End PICC_DumpDetailsToSerial()
+
 /**
  * Dumps memory contents of a MIFARE Classic PICC.
  * On success the PICC is halted after dumping the data.
diff --git a/MFRC522.h b/MFRC522.h
index 6c3da7f..e003451 100644
--- a/MFRC522.h
+++ b/MFRC522.h
@@ -272,8 +272,8 @@ public:
 	};
 	
 	// PICC types we can detect. Remember to update PICC_GetTypeName() if you add more.
-	// last value set to 255, hints compiler to use byte instead of default integer, works for arduino ide to save ram and flash
-	enum PICC_Type {
+	// last value set to 0xff, then compiler uses less ram, it seems some optimisations are triggered
+	enum PICC_Type : byte {
 		PICC_TYPE_UNKNOWN		,
 		PICC_TYPE_ISO_14443_4	,	// PICC compliant with ISO/IEC 14443-4 
 		PICC_TYPE_ISO_18092		, 	// PICC compliant with ISO/IEC 18092 (NFC)
@@ -283,12 +283,12 @@ public:
 		PICC_TYPE_MIFARE_UL		,	// MIFARE Ultralight or Ultralight C
 		PICC_TYPE_MIFARE_PLUS	,	// MIFARE Plus
 		PICC_TYPE_TNP3XXX		,	// Only mentioned in NXP AN 10833 MIFARE Type Identification Procedure
-		PICC_TYPE_NOT_COMPLETE	= 255	// SAK indicates UID is not complete.
+		PICC_TYPE_NOT_COMPLETE	= 0xff	// SAK indicates UID is not complete.
 	};
 	
 	// Return codes from the functions in this class. Remember to update GetStatusCodeName() if you add more.
-	// last value set to 255, hints compiler to use byte instead of default integer, works for arduino ide to save ram and flash
-	enum StatusCode {
+	// last value set to 0xff, then compiler uses less ram, it seems some optimisations are triggered
+	enum StatusCode : byte {
 		STATUS_OK				,	// Success
 		STATUS_ERROR			,	// Error in communication
 		STATUS_COLLISION		,	// Collission detected
@@ -297,7 +297,7 @@ public:
 		STATUS_INTERNAL_ERROR	,	// Internal error in the code. Should not happen ;-)
 		STATUS_INVALID			,	// Invalid argument.
 		STATUS_CRC_WRONG		,	// The CRC_A does not match
-		STATUS_MIFARE_NACK		= 255	// A MIFARE PICC responded with NAK.
+		STATUS_MIFARE_NACK		= 0xff	// A MIFARE PICC responded with NAK.
 	};
 	
 	// A struct used for passing the UID of a PICC.
@@ -381,16 +381,21 @@ public:
 	StatusCode PCD_MIFARE_Transceive(byte *sendData, byte sendLen, bool acceptTimeout = false);
 	// old function used too much memory, now name moved to flash; if you need char, copy from flash to memory
 	//const char *GetStatusCodeName(byte code);
-	const __FlashStringHelper *GetStatusCodeName(StatusCode code);
-	PICC_Type PICC_GetType(byte sak);
+	static const __FlashStringHelper *GetStatusCodeName(StatusCode code);
+	static PICC_Type PICC_GetType(byte sak);
 	// old function used too much memory, now name moved to flash; if you need char, copy from flash to memory
 	//const char *PICC_GetTypeName(byte type);
-	const __FlashStringHelper *PICC_GetTypeName(PICC_Type type);
+	static const __FlashStringHelper *PICC_GetTypeName(PICC_Type type);
+	
+	// Support functions for debuging
 	void PCD_DumpVersionToSerial();
 	void PICC_DumpToSerial(Uid *uid);
+	void PICC_DumpDetailsToSerial(Uid *uid);
 	void PICC_DumpMifareClassicToSerial(Uid *uid, PICC_Type piccType, MIFARE_Key *key);
 	void PICC_DumpMifareClassicSectorToSerial(Uid *uid, MIFARE_Key *key, byte sector);
 	void PICC_DumpMifareUltralightToSerial();
+	
+	// Advanced functions for MIFARE
 	void MIFARE_SetAccessBits(byte *accessBitBuffer, byte g0, byte g1, byte g2, byte g3);
 	bool MIFARE_OpenUidBackdoor(bool logErrors);
 	bool MIFARE_SetUid(byte *newUid, byte uidSize, bool logErrors);
diff --git a/README.rst b/README.rst
index ecb8958..87ec696 100644
--- a/README.rst
+++ b/README.rst
@@ -13,36 +13,43 @@ Interface (SPI) interface.
 Set the UID, write to sector 0, and unbrick Chinese UID changeable MIFARE cards.
 
 
-.. _pin layout:
+.. _compatible boards:
+Compatible boards
+----------
 
+This library is compatible to Teensy and ESP8266, but not all examples are available for every board. Also you have to change pins, see `pin layout`_.
+
+
+.. _pin layout:
 Pin Layout
 ----------
 
 The following table shows the typical pin layout used:
 
-+-----------+----------+-------------------------------------------------------------+--------------------------+
-|           | PCD      | Arduino                                                     | Teensy                   |
-|           +----------+-------------+---------+---------+---------------+-----------+--------+--------+--------+
-|           | MFRC522  | Uno         | Mega    | Nano v3 |Leonardo/Micro | Pro Micro | 2.0    | ++ 2.0 | 3.1    |
-+-----------+----------+-------------+---------+---------+---------------+-----------+--------+--------+--------+
-| Signal    | Pin      | Pin         | Pin     | Pin     | Pin           | Pin       | Pin    | Pin    | Pin    |
-+===========+==========+=============+=========+=========+===============+===========+========+========+========+
-| RST/Reset | RST      | 9 [1]_      | 5 [1]_  | D9      | RESET/ICSP-5  | RST       | 7      | 4      | 9      |
-+-----------+----------+-------------+---------+---------+---------------+-----------+--------+--------+--------+
-| SPI SS    | SDA [3]_ | 10 [2]_     | 53 [2]_ | D10     | 10            | 10        | 0      | 20     | 10     |
-+-----------+----------+-------------+---------+---------+---------------+-----------+--------+--------+--------+
-| SPI MOSI  | MOSI     | 11 / ICSP-4 | 51      | D11     | ICSP-4        | 16        | 2      | 22     | 11     |
-+-----------+----------+-------------+---------+---------+---------------+-----------+--------+--------+--------+
-| SPI MISO  | MISO     | 12 / ICSP-1 | 50      | D12     | ICSP-1        | 14        | 3      | 23     | 12     |
-+-----------+----------+-------------+---------+---------+---------------+-----------+--------+--------+--------+
-| SPI SCK   | SCK      | 13 / ICSP-3 | 52      | D13     | ICSP-3        | 15        | 1      | 21     | 13     |
-+-----------+----------+-------------+---------+---------+---------------+-----------+--------+--------+--------+
++-----------+----------+---------------------------------------------------------------+--------------------------+
+|           | PCD      | Arduino                                                       | Teensy                   |
+|           +----------+-------------+---------+---------+-----------------+-----------+--------+--------+--------+
+|           | MFRC522  | Uno         | Mega    | Nano v3 |Leonardo / Micro | Pro Micro | 2.0    | ++ 2.0 | 3.1    |
++-----------+----------+-------------+---------+---------+-----------------+-----------+--------+--------+--------+
+| Signal    | Pin      | Pin         | Pin     | Pin     | Pin             | Pin       | Pin    | Pin    | Pin    |
++===========+==========+=============+=========+=========+=================+===========+========+========+========+
+| RST/Reset | RST      | 9 [1]_      | 5 [1]_  | D9      | RESET / ICSP-5  | RST       | 7      | 4      | 9      |
++-----------+----------+-------------+---------+---------+-----------------+-----------+--------+--------+--------+
+| SPI SS    | SDA [3]_ | 10 [2]_     | 53 [2]_ | D10     | 10              | 10        | 0      | 20     | 10     |
++-----------+----------+-------------+---------+---------+-----------------+-----------+--------+--------+--------+
+| SPI MOSI  | MOSI     | 11 / ICSP-4 | 51      | D11     | ICSP-4          | 16        | 2      | 22     | 11     |
++-----------+----------+-------------+---------+---------+-----------------+-----------+--------+--------+--------+
+| SPI MISO  | MISO     | 12 / ICSP-1 | 50      | D12     | ICSP-1          | 14        | 3      | 23     | 12     |
++-----------+----------+-------------+---------+---------+-----------------+-----------+--------+--------+--------+
+| SPI SCK   | SCK      | 13 / ICSP-3 | 52      | D13     | ICSP-3          | 15        | 1      | 21     | 13     |
++-----------+----------+-------------+---------+---------+-----------------+-----------+--------+--------+--------+
 
 .. [1] Configurable, typically defined as RST_PIN in sketch/program.
 .. [2] Configurable, typically defined as SS_PIN in sketch/program.
 .. [3] The SDA pin might be labeled SS on some/older MFRC522 boards. 
 
 
+.. _hardware:
 Hardware
 --------
 
@@ -133,6 +140,7 @@ Troubleshooting
   #. Hardware may be corrupted, most products are from china and sometimes the quality is really poor. Contact your seller.
   #. Newer versions of Mifare cards like DESFire/Ultralight maybe not work according to missing authentification, see `security`_ or different `protocol`_.
 
+
 * **My mobile phone doesn't recognize the MFRC522** or **my MFRC522 can't read data from other MFRC522**
 
   #. Card simmulation is not supported.
@@ -146,6 +154,7 @@ Troubleshooting
   #. If hardware: buy a more expensive like PN532 (supports NFC and many more, but costs about $15)
 
 
+.. _license:
 License
 -------
 This is free and unencumbered software released into the public domain.
diff --git a/examples/DumpInfo/DumpInfo.ino b/examples/DumpInfo/DumpInfo.ino
index a6345b1..325b7ca 100644
--- a/examples/DumpInfo/DumpInfo.ino
+++ b/examples/DumpInfo/DumpInfo.ino
@@ -47,7 +47,7 @@ void setup() {
 	SPI.begin();			// Init SPI bus
 	mfrc522.PCD_Init();		// Init MFRC522
 	mfrc522.PCD_DumpVersionToSerial();	// Show details of PCD - MFRC522 Card Reader details
-	Serial.println(F("Scan PICC to see UID, type, and data blocks..."));
+	Serial.println(F("Scan PICC to see UID, SAK, type, and data blocks..."));
 }
 
 void loop() {
diff --git a/keywords.txt b/keywords.txt
index 07fea88..ae2a39e 100644
--- a/keywords.txt
+++ b/keywords.txt
@@ -64,11 +64,16 @@ PCD_MIFARE_Transceive	KEYWORD2
 GetStatusCodeName	KEYWORD2
 PICC_GetType	KEYWORD2
 PICC_GetTypeName	KEYWORD2
+
+# Support functions for debuging
 PCD_DumpVersionToSerial	KEYWORD2
 PICC_DumpToSerial	KEYWORD2
+PICC_DumpDetailsToSerial	KEYWORD2
 PICC_DumpMifareClassicToSerial	KEYWORD2
 PICC_DumpMifareClassicSectorToSerial	KEYWORD2
 PICC_DumpMifareUltralightToSerial	KEYWORD2
+
+# Advanced functions for MIFARE
 MIFARE_SetAccessBits	KEYWORD2
 MIFARE_OpenUidBackdoor	KEYWORD2
 MIFARE_SetUid	KEYWORD2