28440

Web Site: www.parallax.com Forums: forums.parallax.com Sales: sales@parallax.com Technical: support@parallax.com Office: (916) 624-8333 Fax: (916) 624-8003 Sales: (888) 512-1024 Tech Support: (888) 997-8267 RFID Read/Write Module, Serial (#28440) Designed in cooperation with Grand Idea Studio (www.grandideastudio.com), the Parallax Radio Frequency Identification (RFID) Read/Write Module provides a low-cost solution to read and write passive RFID transponder tags up to 3 inches away. The RFID transponder tags provide a unique serial number and can store up to 116 bytes of user data, which can be password protected to allow only authorized access. The RFID Read/Write Module can be used in a wide variety of hobbyist and commercial applications, including access control, user identification, robotics navigation, inventory tracking, payment systems, car immobilization, and manufacturing automation. Features y y y y Low-cost method for reading and writing passive, 125 kHz RFID transponder tags Up to 116 bytes of user data storage on a single tag Optional security features prevent tag from being read or written without password Bi-color LED for visual indication of status Key Specifications y y y Power requirements: +5 VDC; < 10 mA idle, approx. 100-200 mA active Communication: asynchronous serial 9600 bps, (8N1); 5 V TTL-level, non-inverted Dimensions: 3.25 x 2.45 in (8.26 x 6.2 cm) RFID Tag Compatibility The RFID Read/Write Module works exclusively with the EM Microelectronics EM4x50 1kbit R/W transponder tags. A variety of different tag types and styles exist, with the most popular ones made available from Parallax. Each tag contains a unique, read-only serial number (one of 232, or 4,294,967,296 possible combinations) and 116 bytes of user data area stored in a non-volatile EEPROM (Electrically Erasable Read Only Memory). The user data area can be optionally secured with a 32-bit password to allow only authorized read and write operations. The RFID Read/Write Module provides, with a single command, legacy support for the EM Microelectronics EM4100 read-only tags that are used with Parallax’s RFID Card Reader Serial (#28140) and USB (#28340). Copyright © Parallax Inc. RFID Read/Write Module, Serial (#28440) v1.0 6/29/2010 Page 1 of 10 Connections The RFID Read/Write Module easily interfaces to any host microcontroller using only four connections (VCC, SIN, SOUT, GND). Pin Pin Name Type Function 1 VCC P System power. +5V DC input. 2 SIN I Serial input from host. TTL-level interface, 9600 bps, 8 data bits, no parity, 1 stop bit. 3 SOUT O Serial output to host. TTL-level interface, 9600 bps, 8 data bits, no parity, 1 stop bit. System ground. Connect to power supply’s ground (GND) terminal. Note: Type: I = Input, O = Output, P = Power, G = Ground 4 GROUND G Use the following example circuit for connecting the Parallax RFID Read/Write Module: Copyright © Parallax Inc. RFID Read/Write Module, Serial (#28440) v1.0 6/29/2010 Page 2 of 10 Usage There are many ways to use the RFID Read/Write Module and associated tags, but the three most common are as follows: 1) Read Only: Read the tag’s unique, non-changing 32-bit serial number 2) Read/Write: Read from and write up to 116 bytes of publicly accessible user data on the tag 3) Read/Write (Protected): Read from and write up to 116 bytes of password-protected user data on the tag. In this mode, you must enter the correct 32-bit password in order for read and write operations to be successful. The RFID Read/Write Module is controlled by the host via a serial communications interface. The unit waits in an idle state until it receives a valid header and command from the host, at which time the module will perform the command and return a status/error byte indicating a success or failure and command-specific data (if any). The module will then re-enter the idle state and wait for the next valid header and command. A visual indication of the RFID Read/Write Module’s state is given with the on-board LED (Light Emitting Diode). When the module is successfully powered-up and is in an idle state, the LED will be GREEN; when the module is in an active state (for example, searching for a valid tag or performing an operation on the tag), the LED will be RED. The face of the tag should be held parallel to the front or back face of the antenna (where the majority of RF energy is emitted). If the tag is held sideways (for example, perpendicular to the antenna), you'll either get no reading or a poor reading distance. Only one transponder tag should be held up to the antenna at any time. The use of multiple tags at one time will cause tag collisions and the reader may not detect any of them. The tags available in the Parallax store have a read distance of approximately 3 inches. Actual distance may vary slightly depending on the size of the transponder tag and environmental conditions of the application. Communication Protocol The RFID Read/Write Module is controlled by the host via a standard, asynchronous serial communications interface configured at 9600 bps, 8 data bits, no parity, 1 stop bit, and least significant bit first (8N1). The serial data expected and transmitted by the RFID Read/Write Module is 5V TTL-level, non-inverted. To communicate with the RFID Read/Write Module, the user must first send a three-byte header string of !RW (in ASCII), followed by the desired single-byte command (in hexadecimal). Certain commands require additional data to be sent along with the command. A status/error byte and a varying number of data bytes will be returned depending on the command called. Copyright © Parallax Inc. RFID Read/Write Module, Serial (#28440) v1.0 6/29/2010 Page 3 of 10 Command Set 0x01: RFID_Read Read data from a specified address Input: Address location (1 byte), valid locations are 1-33 decimal Output: Status byte (1 byte) + data (4 bytes) Example: SEROUT RFID_TX, Baud, ["!RW", RFID_Read, ADDR_Serial] SERIN RFID_RX, Baud, [err, STR data\4] ' Read tag's serial number ' Get status byte & data bytes 0x02: RFID_Write Write data to a specified address Input: Address location (1 byte), valid locations are 3-31 decimal + data (4 bytes) Output: Status byte (1 byte) Example: ' Write $FEEDBEEF to address 3 (User Data Area) SEROUT RFID_TX, Baud, ["!RW", RFID_Write, 3, $FE, $ED, $BE, $EF] SERIN RFID_RX, Baud, [err] ' Get status byte Note: After writing the specified data to the tag, the RFID Read/Write Module automatically performs a read function to verify that the data has properly been written. 0x03: RFID_Login Login to the tag (required to use password protection features) Input: Password (4 bytes), default = 0x00000000 Output: Status byte (1 byte) Example: ' Login to tag with password SEROUT RFID_TX, Baud, ["!RW", RFID_Login, $00, $00, $00, $00] SERIN RFID_RX, Baud, [err] ' Get status byte 0x04: RFID_SetPass Change the tag’s password Input: Current password (4 bytes) + new password (4 bytes) Output: Status byte (1 byte) Example: ' Change password from current ($00000000) to new ($FEEDBEEF) SEROUT RFID_TX, Baud, ["!RW", RFID_SetPass, REP $00\4, $FE, $ED, $BE, $EF] SERIN RFID_RX, Baud, [err] ' Get status byte Copyright © Parallax Inc. RFID Read/Write Module, Serial (#28440) v1.0 6/29/2010 Page 4 of 10 0x05: RFID_Protect Enable (lock) or disable (unlock) the tag’s password protection. Input: Mode (1 byte), 0x00 to unlock, 0x01 to lock Output: Status byte (1 byte) Example: SEROUT RFID_TX, Baud, ["!RW", RFID_Protect, 1] ' Lock the tag SERIN RFID_RX, Baud, [err] ' Get status byte Note: When the tag is locked, a successful login using the RFID_Login command is required before you can enable/disable password protection, change the tag’s password, or read/write to the tag. If the tag is locked and you are not successfully logged in, the RFID_Read command will return four bytes of 0x00 in place of the actual user data and the RFID_Write command will return an error. 0x06: RFID_Reset Log out and reset the tag. Input: None Output: Status byte (1 byte) Example: SEROUT RFID_TX, Baud, ["!RW", RFID_Reset] SERIN RFID_RX, Baud, [err] ' Reset the tag ' Get status byte Note: All user data will remain stored on the tag. You will need to re-login using RFID_Login if you want to access a locked tag after calling this command. You can also reset the tag by removing it from the proximity of the RFID Read/Write Module. 0x0F: RFID_ReadLegacy Read the 40-bit unique serial number from an EM Microelectronics EM4100 read-only tag (used with Parallax’s RFID Card Reader Serial, #28140, and USB, #28340). Input: None Output: Header (1 byte) + data (10 bytes) + footer (1 byte) Example: SEROUT RFID_TX, Baud, ["!RW", RFID_ReadLegacy] SERIN RFID_RX, Baud, [header, STR data\10, footer] ' Read EM4100 unique serial # ' Get header, data, and footer Note: The header and footer are used to identify that a correct string has been received from the reader (they correspond to a line feed and carriage return characters, respectively). The middle ten bytes are the tag's unique ID sent in a printable ASCII string. For example, for a tag with a valid ID of 0F0184F07A, the following bytes would be sent: 0x0A, 0x30, 0x46, 0x30, 0x31, 0x38, 0x34, 0x46, 0x30, 0x37, 0x41, 0x0D. Copyright © Parallax Inc. RFID Read/Write Module, Serial (#28440) v1.0 6/29/2010 Page 5 of 10 Error Checking The RFID Read/Write Module responds to each command with a single-byte status/error code in hexadecimal format followed by any returned data, if applicable. In most standard implementations, the user will repeatedly call the desired function until the ERR_OK status byte is returned, indicating that the function successfully completed with no errors. For scenarios where more error checking is desired, the RFID Read/Write Module provides detailed error code values: Value Name Description 0x01 ERR_OK No Errors 0x02 ERR_LIW Could not find a Listen Window (LIW) from the tag 0x03 ERR_NAK Received a No Acknowledge (NAK), possible communication error or invalid command/data 0x04 ERR_NAK_OLDPW Received a No Acknowledge (NAK) sending the current password during the RFID SetPass command, possible incorrect password 0x05 ERR_NAK_NEWPW Received a No Acknowledge (NAK) sending the new password during the RFID SetPass command 0x06 ERR_LIW_NEWPW Could not find a Listen Window (LIW) from the tag after setting the new password during the RFID SetPass command 0x07 ERR_PARITY Parity error when reading data from the tag Tag Details The RFID Read/Write Module works exclusively with the EM Microelectronics-Marin SA EM4x50 1kbit R/W transponder tags at 125kHz. A variety of different tag types and styles exist with the most popular ones made available from Parallax. The memory map and corresponding address locations for the EM4x50 tag are shown below. Each address holds a 32-bit (4 byte) value. Address (decimal) Register Description 0 ADDR_Password Password (not readable) 1 ADDR_Protect Protection word 2 ADDR_Control Control word 3-31 User Data Area Non-volatile EEPROM storage area for user data (116 bytes) 32 ADDR_Serial Device serial number (unique, read-only) 33 ADDR_DeviceID Device identification (used to identify tag family, read-only) The User Data Area can be optionally secured using a 32-bit password to allow only authorized read and write operations. This password is stored in ADDR_Password and can be changed by the user via the RFID_SetPass command with knowledge of the current password. For security reasons, it cannot be read. As such, if your tag is password-protected and you forget the tag’s password, you will be unable to retrieve the contents of the User Data Area. ADDR_Protect and ADDR_Control are modified directly by the RFID Read/Write Module and, in normal scenarios, should not be changed by the user. Copyright © Parallax Inc. RFID Read/Write Module, Serial (#28440) v1.0 6/29/2010 Page 6 of 10 ADDR_Serial is a unique, read-only serial number with one of 232, or 4,294,967,296, possible values. It cannot be changed by the user. ADDR_DeviceID is a read-only value used to identify the specific tag family (for example, EM4150). The 32-bit value contains a family code, version code, reserved/unused bits, and a checksum value. It cannot be changed by the user. Further details of the EM4x50 tag can be found at: www.emmicroelectronic.com/Products.asp?IdProduct=159 Electrical Characteristics At VCC = +5.0V and TA = 25ºC unless otherwise noted Parameter Symbol Specification Test Conditions Unit Min. Typ. Max. Supply Voltage VCC --- 4.5 5.0 5.5 V Supply Current, Idle IIDLE --- --- 9.4 --- mA Supply Current, Active ICC --- --- 108 200 mA Input LOW voltage VIL +4.5V