The DigiClip system allows the tracking, synchronization and and integrity control of paper-based documents with their electronic counterparts. Particles were integrated in a paper clip and allowed to obtain location information for a document. In conjuction with a document management system, the DigiClip device enabled a physical notifcation of changes of the electronic document. The sensors of the DigiClip device allow further the application of integrity rules on the physical document, such as document integrity on a single page-level, handling constraints and location restrictions. The DigiClip device was built by the Adam Eames who did an internship at SAP in cooperation with TecO.
Features: The DigiClip incorporates a capacitive page-count sensor. Particle XBridges are used to enable a room-level tracking. Sensors like acceleration sensor and light sensor are used to detect situation like "put into a bag", or "put below a bunch of other papers". LEDs on the board indicate the state changes of the electronic document associated with the physical one. As a result, the DigiClip system is able to keep electronic and paper-based documents in sync.

DigiClip on papers
DigiClip Closeup

DigiClip on papers

DigiClip close-up



The DigiClip device is built on top of a Particle core board utilizing a customized sensor board integrating an acceleration sensor ADXL210, light sensor TSL250, and a capacitive page count sensor. Latter is based on a capacitor formed by 2 metal plates wrapped around the pages of a paper-based document. The distance between the plates is discriminated by the number of pages in between. We assumed that equal-thick pages in all our experiments. A DAC on the device generates a sinoid voltage across the capacitor and an ADC measures it. The sensor is outlined in the following two figures presenting a schematic overview and measurement results. A mathematical explaination is summarized in this document.

Capacitive Page Count Sensor

Page count sensor schematic
Page count measurements

Fig. Page count sensor schematic
(click to enlarge)

Fig. Measurement results (click to enlarge)

We also tried out a force sensor - a flexible resistor, but it turns out, that the measurements are too instable to achive an acceptable page count resolution.

In order to track the DigiClip devices and therefore the documents, we deployed a cell-of-origin location system using the Particle XBridges. The following figures depict the overall system.
The DigiClip device is integrated in a document management system. The database holds the actual state of physical document. The actual state is sensed and communicated by the DigiClip device attached to the document via bridges which span a communication cell. The user configures the DigiClip and receives changes of states, e.g. position change or alerts.

System architecture
Location System Screenshot

Fig. DigiClip System overview (click to enlarge)

Fig. DigiClip location system
(click to enlarge)

DigiClip 2


The DigiClip device went under a redesign to account for usability and easy deployment in various scenarios. As a result it became a handy device which is packed in a plastic box, LED positions were standardized and a button was added. The DigiClip 2 integrates a variety of sensors, such as temperature, light, acceleration, microphone. It can be easily augment by further actuators like speaker and provides a 8 pin interface for further connections. Although it lost the page count sensor, DigiClip 2 quickly became a platform for investigating SAP's Smart-Item scenarios. Such scenarios incoporate physical entities which are augmented by electronic devices such as the DigiClip in order to execute business logic at the point of action. We explore such scenarios in the CoBIs project. A DigiClip variation was the BlueClip - a bluetooth enabled DigiClip in the same housing and sensors. It utilizes a zeevo module for bluetooth communication. Remarkable is the energy consumption which required an additional battery compared to regular Particle Computer technology. The blueclip was build to enable the integration of standard consumer electronics in DigiClip networks. We realized an authenticated document signature using a regular cell phone as a proof of concept. A connector board enabled bridging between the two platforms and communication standards. Download an animation of the DigiClip/BlueClip.

DigiClip2 DigiClip - BlueClip

Fig. DigiClip 2

Fig. DigiClip and BlueClip

Recently, the location system based on DigiClip was improved. Instead of using RF in the cell-of-origin system, we incorporate an IR beaconing system. The beacons were generated by a separate transmitter. The DigiClip's 8 pin port was used to connect a TSOP IR receiver. This allows accurate readings in situations where unreliable RF communication is expected, e.g. industrial areas. Surrounding light was filtered out by software.

DigiClip TSOP connector
DigiClip TSOP connector

Fig. DigiClip and TSOP receiver



The DigiClip was presented in papers on IWSAWC 2004 and Pervasive 2004. Apart from scientific publications, the DigiClip attracted a lot of publicity. It was presented on CeBIT 2004 to the German chancellor Gerhard Schröder and on SAPPHIRE 2004,SAP Research Labs, Palo Alto, SAPPHIRE Australia, "Tag der Informatik" at the University of Darmstadt, Multimedia Forum at the University of Karlsruhe . Articles in SAP magazines utilized the DigiClip to push the idea of Smart-Items in business processes. As a result, the DigiClip is used in scenarios of the CoBIs project implementing collaborative business processes in safety scenarios of BP involving chemical drums.