View Full Version : Fingerprint Scanner

05-01-2006, 06:56 PM
I would like to figure out a way to connect a fingerprint scanner to a stamp.· Has any one seen a sensor that can be used with a stamp?· Or has any successfully done this type of project?


05-01-2006, 08:04 PM
I believe the amount of data and speed needed to capture it from a "fingerprint scanner" probably rules out the BS2.

Bruce Bates
05-01-2006, 08:44 PM
Tim -

A good deal will depend on the exact biometric unit you are seeking to use, and the requirements it makes on the processor. My own experience with biometrics, specifically using the PBASIC Stamp, or in general with any other microcontroller is quite limited, but I'll be happy to share what little I have learned.

The first concern is obviously the hardware interface. Since many of these biometric devices will operate successfully with an ordinary·PC using an RS-232 interface using a DB-9 serial connection, one merely needs to check to see that half-duplex transmission (with or without flow control) is acceptable. This is opposed to a potential requirement that the processor be capable of full duplex, which can really only be met by a processor using a hardware UART, extremely high processor speed, or hardware interrupt capability. This requrement will not wholly negate a PBASIC Stamp per se, but will cause you to have to·make some additional, external hardware concessions (external RS-232 buffer or UART).

The second and third concerns·are the amount of physical data the micro-processor will be required to manipulate, and what you are required to do with the data output from such a biometric sensor. ·While it might be trivial for a PC to·accept a couple of hundred bytes of data, which it must then·present to·(say) an MS Access Fingerprint Database, this is quite far beyond the capabilities of the PBASIC Stamp with its limited RAM, and lower speed. Yet, if the exchange of information was (say) more like the following, this might be quite doable:

- - - Hypothetical Example ONLY - Loose System Flow defined:

Enable biometric device from Stamp, announce failure if necessary

Display "Place index finger on lit screen"

Check for proper finger placement

Cause fingerprint scan to proceed

Accept pattern matching mask [PMM] (18-20 bytes, or·144+ bits)

Accept and attach ID data (3-4 byte) prefix to PMM and re-transmit to PC

Accept status data (1-2 bytes) returned from PC (verification)

Announce results on LCD or serial printer (log data)

Unlatch gate or door if status permits or perhaps sound alarm if not

Check for passage through gate/door

Ensure safe re-latching of gate/door
- - -

It would also be wise to investigate any timing requirements, and/or any minimum/maximim baud rates which may be required by the attached devices.

I hope that is helpful information.


Bruce Bates

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05-02-2006, 08:25 AM

Thanks very much for the feedback.· Have you experimented with a sensor of this type?· i am bummed that a stamp might not work.


Paul Baker
05-02-2006, 11:37 AM
To my knowlege the existing systems have a sensor which only provides the raw data to·a PC·running software to do the detection, so all the "magic" happens on the PC end. You would have to replicate this software which is not trival (just getting a fingerprint aligned with the reference print isnt easy, you must be able to translate in two directions and compensate for rotation of the print) and the issue is further complicated by the fact that any company producing such systems will jelously guard the method of how they do it.


Bruce Bates
05-02-2006, 11:59 AM
Tim -

No, I have never worked specifically with a fingerprint scanner per se, but I have assisted others in doing so.


Bruce Bates

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