There exist so-called Digital Pens, which will record what they are writing electronically, while writing on paper. These pens belong to two categories:
- The kind that require special paper.
- The kind that require a receiver be attached to the top of the sheet, which senses the positions of the pen during writing, but which do not require special paper.
The is a digital pen of the second kind, of which I happen to own one.
In general, I do not find this type of pen very useful, because the need does not arise often, to be writing on paper, yet to be digitizing what is written anyway. However, I have this pen, and have in the past installed Windows software to download its writings onto my PC.
I felt that it would be a challenge to get this relic to work again, while using Linux software to download its data. For that purpose, it was helpful to note, that the hardware is of the ‘‘ variety, regardless of how it was branded. And then it was easy to find a special, Linux, software-project, the aim of which was to do exactly that.
This software only comes in binary form, packaged for Ubuntu. Using Debian, we do not have a mechanism for PPAs. And so the only way for me to get it running, was to custom-compile it, which I easily did.
Aside from custom-compiling, I needed to create the following file:
/etc/udev/rules.d/50-hidraw.rules : ACTION=="add", KERNEL=="hidraw*", MODE="0666"
I should note that my version of pen is first-generation. I cannot guarantee that any of this will work with an or an -type pen. I just happened to own a pen which was collecting dust, with the idle thought of wanting to reactivate it.
The version of this pen which I have, has two modes of operation: USB-mode and Bluetooth-mode. The BT-mode has always been rather pointless, because it would need an active wireless connection while I was writing. It was originally meant to work with Android and iOS devices, but lacked in performance.
The ability to download pages of writing that are saved in the receiver-module, has always been limited to working in USB-mode.
And so I am happy to announce, that my project was a success, and that I am able to use the command-line tool to convert captured data to SVG (image) files.
The ability to do OCR on the writing has always required Windows or OS/X, and under Linux, whatever ability we want, to convert the SVG drawings to text, must be supplied by the user or not at all. I am not that far along with it yet.
The way this pen works is interesting to note.
It emits ultrasound-pulses, and the receiver has two microphones. But, if all the receiver could measure, was the difference in the arrival time of the sound-pulses to two microphones, this would not be enough to fix the position of the tip of the pen in 2D, because it would only yield one variable.
Therefore, the pen also emits an infra-red pulse of light, concurrently with its ultrasound-pulse. That way, the receiver can first receive the IR pulse, after which it measures two time-delays… Resulting in 2D positioning.
While the receiver has a battery that recharges through the USB connection – and which took 2 hours and 45 minutes for a full charge – the pen itself does not. It only has two small button-batteries that cannot be recharged, and which I needed to replace, before I could retest everything and be sure it still works.
Now, an error message which appears, that is similar to an error message reported on the site of the software-project, and which was reported as fixed. Fortunately however, the emergence of this error message does not seem to impede the use of the generated files:
dirk@Klystron:~$ cd ~/Documents/Phoenix/Pegasus/test dirk@Klystron:~/Documents/Phoenix/Pegasus/test$ kde-mv * trash:/ dirk@Klystron:~/Documents/Phoenix/Pegasus/test$ m210 dump >notes dirk@Klystron:~/Documents/Phoenix/Pegasus/test$ m210 convert <notes m210: error: failed to read note head: unexpected end-of-file error: convert failed dirk@Klystron:~/Documents/Phoenix/Pegasus/test$ ls -l total 20 -rw-r--r-- 1 dirk dirk 6887 Feb 21 09:44 m210_note_1.svg -rw-r--r-- 1 dirk dirk 7091 Feb 21 09:44 m210_note_2.svg -rw-r--r-- 1 dirk dirk 3906 Feb 21 09:44 notes dirk@Klystron:~/Documents/Phoenix/Pegasus/test$
The main problem here with the OCR, is that ‘
gImageReader‘ expects printed text. I do not know of Linux-based OCR-software, with a special setting for handwriting…
BTW: The batteries in the receiver of this Digital Pen, have always had an unreasonably high rate of self-discharge. It was already like that from the first day I had it.
I suspect this was due, to the device having been stored for a long time – before my purchase – with the battery completely dead. This is usually not good for a rechargeable battery.
But, now that I have taken it out of storage, the problem can only have gotten worse.
A full charge requires about 3 hours, but even after just having put it on the shelf for one day, I need to charge it again for an hour.
I will hope, that if I keep recharging it consistently, the problem may become less acute. It is still important, that I not leave it plugged in for the duration.