A Python driver for the Symbol CS 1504 bar code scanner
One of my cousins works for Symbol, the world’s largest bar code reader manufacturer. The fashionable action today is in RFID, but the humble bar code is relatively untapped at the consumer level. The unexpected success of Delicious Library shows people want to manage their collection of books, CDs and DVDs, and as with businesses, scanning bar codes is the fastest and least error-prone way to do so. Delicious Library supports scanning bar codes with an Apple iSight camera, but you have to wonder how reliable that is.
If you want something more reliable, you need a dedicated bar code scanner. They come in a bewildering array of sizes and shapes, from thin wands to pistol-like models or flat ones like those used at your supermarket checkout counter. For some reason, the bar code scanner world seems stuck in the era of serial ports (or worse, PS/2 keyboard wedges), but USB models are available, starting at $70 or so. They emulate a keyboard – when you scan a bar code, they will type in the code (as printed on the label), character by character so as to not overwhelm the application, and follow with a carriage return, which means they can work with almost anything from terminal-based applications to web pages. Ingeniously, most will allow you to program the reader’s settings using a booklet of special bar codes that perform changes like enabling or disabling ISBN decoding, and so on.
The problem with tethered bar code readers is, they are not very convenient if you are trying to catalog items on a bookshelf or read in UPC codes in a supermarket. Symbol has a unit buried deep inside its product catalog, the CS 1504 consumer scanner. This tiny unit (shown below with a canister of 35mm film for size comparison) can be worn on a key chain, although I would worry about damaging the plastic window. Most bar code readers are hulking beasts in comparison. It has a laser bar code scanner: just align the line it projects with the bar code and it will chirp once it has read and memorized the code. The memory capacity is up to 150 bar code scans with timestamps, or 300 without timestamps. The 4 silver button batteries (included) are rated for 5000 scans — AAA would have been preferable, but I guess the unit wouldn’t be so compact, but it is clear this scanner was not intended for heavy-duty commercial inventory tracking purposes.
I bought one to simplify the process of listing books with BookCrossing (even though their site is not optimized for bar code readers), but you have other interesting uses like finding out more about your daily purchases such as nutritional information or whether the company behind them engages in objectionable business practices. I can also imagine sticking preprinted bar-coded asset tracking tags on inventory (e.g. computers in the case of an IT department), and keeping track of them with this gizmo. People who sell a lot of books or used records through Amazon.com can also benefit as Amazon has a bulk listing service to which you can upload a file with barcodes. An interesting related service is the free UPC database.
Mac OS X driver available.
The scanner ships without any software. Symbol mostly sells through integrators to corporations that buy hundreds or thousands of bar code scanners for inventory or point of sale purposes, and they are not really geared to be a direct to consumer business with all the customer support hassles that entails. There are a number of programs available, mostly for Windows, but they don’t seem to have that much by way of functionality to justify their high prices, often as expensive as the scanner itself.
Symbol does make available a SDK to access the scanner, including complete documentation of the protocol used for the device. While you do have to register, they do not make you go through the ridiculous hoops you have to pass to access to the Photoshop plug-in SDK or the Canon RAW decoding SDK. The supplied libraries are Windows-only, however, so I wrote a Python script that works on both Windows and Mac OS X (and probably most UNIX implementations as well, although you will have to use a serial port). The only dependency is the pySerial module.
By default, it will set the clock on the scanner, retrieve the recorded bar codes, correct the timestamps for any drift between the CS 1504’s internal clock and that of the host computer, and if successful clear the unit’s memory and dump the acquired bar codes in CSV format to standard output. The script will also decode ISBN codes (the CS 1504 does not appear to do this by itself in its default configuration). As it is written in Python, it can easily be extended, although it is probably easier to work off the CSV file.
The only configuration you have to do is set the serial port to use at the top of the script (it should do the right thing on a Mac using the Prolific driver, and the Windows driver seems to always use COM8 but I have no way of knowing if this is by design or coincidence). The program is still very rough, specially as concerns error recovery, and I appreciate any feedback.
A sample session follows:
ormag ~>python cs1504.py > barcodes.csv Using device /dev/cu.usbserial... connected serial# 000100000003be95 SW version NBRIKAAE reading clock for drift clock drift 0:00:01.309451 resetting scanner clock... done reading barcodes... done (2 read) clearing barcodes... done powering down... done ormag ~>cat barcodes.csv UPCA,034571575179,2006-03-27 01:08:48 ISBN,1892391198,2006-03-27 01:08:52
At the prompting of some Windows users, I made a slightly modified version, win_cs1504.py, that will copy the barcodes to the clipboard, and also insert the symbology, barcode and timestamp starting on the first free line in the active Excel spreadsheet (creating one if necessary).
Just to make it clear: I hereby place this code in the public domain.
For Windows users, I have put up videos describing how to install the Prolific USB to serial driver, Python and requisite extensions, and how to use the program itself.
I moved the script over to GitHub. Please file bug reports and enhancement requests there. Fatherhood and a startup don’t leave me much time to maintain this, so I make no promises, but this should allow people who make fixes to contribute them back (or fork).