What Do You Need to Track?
November 07, 2018
Single-Wire Serial EEPROMs Provide Unique Serial Numbers to Help Identify and Track Detachable Components.
For developers of many applications, the ability to identify and track detachable items—like connection wires, plastic tubes and printer cartridges—has long been considered a nice-to-have feature. However, the difficulty of figuring out a low-cost way to add this capability to the manufacturing process usually results in this idea being left behind on the white board.
But Microchip has an answer to this design challenge. The AT21CS01 is one of Microchip’s highly reliable Single-Wire 1 Kb Serial EEPROMs that comes with a unique factory-programmed 64-bit serial number. It also offers a separate 128-bit user-writable space and four 256-bit EEPROM zones. The user can choose to make all five EEPROM zones (128-bit writable space and four 256-bit blocks) permanently written at any time so they can’t be hacked or accidentally changed.
The AT21CS01 uses a modified I2 C interface that allows the device to extract power (Vcc) from the reading and writing sequences (pin SI/O). The second connection is system ground (pin Vss).
With this solution in mind, here are two examples of how the AT21CS01 1 Kb Serial EEPROM can be effectively used to provide a relatively low-cost solution for identifying and tracking detachable components.
Challenge #1 Medical Plastic Tubing
Design Goals: A medical device uses a plastic tube that needs to be tracked. A new plastic tube must be assigned to and stay with each patient who uses the device. The base machine also may need to be shared with other patients. The device needs to reconfirm the tube identity on each insertion and read the tube usage history. The tube’s memory needs to track items such as patient ID number, timestamps for when it was used and possibly other data.
Concerns: The design uses low-temperature plastics that can’t endure high temperature cycles. Contact reliability is important. Also, solder paste chemicals should not be used near the inhalation plastics.
Solution: An AT21CS01 in a two-pin XSFN package is a good option for this design. As shown in the illustration on the left side of Figure 1, this XSFN package has flat insertion bar contacts. The encasing plastic connector end has one flat side and is formed of hard plastic. The device is epoxied into place, allowing both pins (SI/O and GND) to connect on insertion. The tubing is otherwise unencumbered. The base machine can then identify the tubing, get tracking information and history detail, and can update the tubing usage information while connected.
Challenge #2 Fiber Optic Cable
Design Goals: In a fiber optic application, the cable needs the capability to self-identify and provide information including length and other optic parameters, connection history, serial number and manufacturing details. The cable also needs to be capable of hot-swapping. The cable can also contain tracking codes that make counterfeiting more difficult.
Concerns: The primary issues are cost and high electrostatic discharge tolerance for hot-swapping situations.
Solution: Once again, the AT21CS01 in a two-pin XSFN package meets the requirements for this application. The AT21CS01 is also available in a 4-ball WLCSP. This requires soldering but is a smaller solution that can then be used with other two-pin contact methods. To resolve the hot-swapping concerns, its ESD specification is ±8 KV contact/±15 KV air discharge.
The Serial Memory Single-Wire Evaluation Kit (DM160232) is an easy-to-use, interactive tool that demonstrates the features, functionality and low-power operation of the AT21CS series of serial EEPROM devices. The evaluation kit is for engineers, developers and decision makers to allow for fast system prototyping using the Single-Wire Interface (SWI) protocol. The kit includes a Graphical User Interface (GUI) that allows you to configure, demonstrate and customize the single-wire serial EEPROM device.
If you are interested in adding tracking or identification capability to your application, visit the AT21CS01 product page, or go to Microchip’s Single-Wire and UNIO Serial EEPROMs page to find other devices that might better meet your design requirements. For assistance with your design, please contact your local Microchip Sales Office.