WaxBee project

[bernard]

@romerof : let's continue this on a separate thread: http://forum.bongofish.co.uk/index.php?topic=2175.0

[merseg]

hey guys,
amazing project. very interesting to read through the threads and see the whole thing unfold.

question - has there been any talk of a derivative project that would run entirely on win as a driver ?
what i mean is something like this:

wacom -------> serial cable ----> waxbee serial driver ---> emulated usb device ------> official wacom driver

similarly to the data flow of using a serial tablet on xp with a usb2serial converter:

wacom --------> serial cable ----> usb2serial cable ------> usb2serial driver -------> emulated serial device -----> official wacom driver.

only suitable for serial tablets of course, not ADB.

[bernard]

this was one avenue I tried quite hard at first. But this was extremely complex and time consuming. I never found a way to emulate a USB device to feed the Wacom driver.  Doing the hardware hack is not fun but it is extremely stable in terms of maintenance for the future.

[bernard]

Other avenues was about rewriting a tablet driver from scratch. On Windows, there are two standards and even if the Microsoft standard (Ink) had samples of driving a Wacom tablet (!!), the real problem lies in the older "WinTab" standard which is the only way to make it work with Adobe products. It is not only an undisclosed and licensed $$ standard (the latest version I mean), it is really hard to implement it. (and I am not even talking about maintaining it for the upcoming Windows versions and flavors).

[merseg]

thanks for the info.
you're right about the complexity, no doubt.
it would however reach a wider range of people that don't know anything about firmware/soldering/etc.
does anyone following this thread have any experience with writing the type of solution i'm talking about? can anyone offer any pointers to reference code?

[bernard]

The hardest part was about feeding the wacom driver. Windows (I assume this about windows only?) now have a full USB and HID stack system. Nobody knowledgable was magically reading our threads, so I searched for people that would potentially have such experience and attempted to contact them. For example, xiaofan chen of the win32 libusb project. Certainly we could try to find more people. I am thinking about developers of usb to serial converters or (commercial) USB diagnostic tools. In particular tools that would allow some sort of playback or device emulation (if such a thing even exists to start with).

[Sicarius]

Thanks for the info and the MAX3232 breakout board pointer.

On the other end of that wire, I have an RJ45 connector wired as a Cisco rollover cable, connected to a RJ45<>DB9 adaptor, connected to a DB9 null-modem gender changer.  Horrible, I know, but it's just temporary until I get a nice enclosure to wedge it all into.

Yipes!  If you ever come across a clean solution, tell us what you did (and at the same time where exactly you connected the CTS/DTR and DTR/DSR jumpers, not everybody can read RS-232 specs - the naming are sometimes "reversed" -- Wacom in particular likes to be the DTE instead of the DCE in their PCB silk screen markings which confuses everything, they are, after all, the center of the world  ).

Finally back again.  Was waiting on a part from China (2 months, it took!) but I've finally finished.

I present for your amusement and edification the fully self-contained and USB powered external Waxbee converter.


And here's how it looks inside:


The wiring is the same before with the notable addition of an LM2577 DC-DC adjustable step-up power converter module.  This little beauty will step up the 5V from USB to the 9V (or more) required by the tablet meaning you no longer need an external power supply.

Also, while troubleshooting, I discovered that the control lines do not need to be connected.  Assuming they are needed for a different model you would short 4<->5 and 6<->9 on the tablet serial connector.

[Aerendraca]

Hi Sicarius,

Nicely done!!

I have a similar little circuit to that LM2577 (looks almost the same), it a DC-DC Buck Step-Down converter which I plan on powering my TFT controller with. You've got to love these Chinese parts, bet it cost less than £5 too!

[bernard]

This is great folks. Now we have a proven solution that avoids opening the tablet. The end result is probably a bit bulkier and more expensive, but not that much considering the tablets are often bulky to start with.  Without the tablet surgery, you have less chance of breaking the tablet (you can still fry it of course and burn your fingers with the soldering iron ) if stuff are not connected correctly.

Would any of you allot a weebit of time to document the schematic of your little dongle marvel? I am not asking for something thorough, but still, something for someone that is not familiar with electronic practices and have hard time reading datasheets. Data like part numbers and which pin (number+name) is connected to what), the DB9 pins, etc. It would add a confidence level to beginners trying to figure out what to solder where. Serial ports tend to be very confusing. Symbol names tend to be reversed (DTE labels vs. DCE labels) and RX/TX naming conventions are often 'flipped' (it depends on the Point Of View).

[Sicarius]

The hardest part was about feeding the wacom driver. Windows (I assume this about windows only?) now have a full USB and HID stack system. Nobody knowledgable was magically reading our threads, so I searched for people that would potentially have such experience and attempted to contact them. For example, xiaofan chen of the win32 libusb project. Certainly we could try to find more people. I am thinking about developers of usb to serial converters or (commercial) USB diagnostic tools. In particular tools that would allow some sort of playback or device emulation (if such a thing even exists to start with).

I'll see about doing a writeup of my project tonight.

In the meantime, concerning the above, have you checked out the USB/IP project?  It's a project for remotely sharing a USB device over the network.   Part of that project is an emulated USB host controller for Windows.  So, once you've decoupled the hardware from the computer, you should be able to replace it with an emulated USB data stream.

http://usbip.sourceforge.net/

[bernard]

Oooh yeah!    That is awesome stuff !!  I never saw this project (or I did not notice there was a Windows client).

Yes, this could mean that any RS-232 to USB converter would be sufficient hardware-wise and all the conversion would occur within the PC.

[Sicarius]

So, here's how it's hooked up:

    Teensy
/------------\        Mini TTL-RS232           DB9
|            |        /-------------\         /---\
|         D2 | ------ | R           |         |1o  \
|         D3 | ------ | T           |         |   o6|
|        +5V | ------ | +5V       R | ------> |2o   |
|        GND | ------ | GND       T | ---\    |   o7| <---\
|            |        \-------------/     \-> |3o   |     |
|            |                                |   o8| <-\ |
|            |        /-------------\         |4o   |   | |
|        +5V | ------ | IN+    OUT+ | ----\   |   o9|   | |
|        GND | ------ | IN-    OUT- | --\ |   |5o  /    | |
|            |        \-------------/   | |   \---/     | |
\------------/        LM2577 module     | |             | |
                                        | \-------------/ |
                                        \-----------------/

The Teensy has two sets of +5V/GND.  The set opposite the USB port should connect to the TTL convertor and the set on the sides of the USB port should go to the LM2577 module.  Those with sharp eyes will notice I have it done differently but in retrospect, this way is better.

The extra parts are:
 - a TTL to RS232 convertor.  There's a link to buy them upthread or you can find them on ebay by searching for "mini TTL RS232" (cost ~$2).  The one I used is connected up on the side opposite the chip.  There are 5 caps on that side; the end with two caps connects to the teensy and the end with three connects to the DB9 serial connector.
 - a LM2577 DCDC power boost module.  I've only found them on ebay; you can search for "LM2577" (cost ~$4)

As for the serial cable, you have two options: get a connector with hood or cut up a cable with a molded end.  A connector with a hood will be easier to wire up but (at least on my tablet) the serial port on the tablet is recessed and the hood won't fit.  You can use something like this port saver to extend it beyond the circuit board.  http://www.monoprice.com/products/product.asp?p_id=1185 (which is what I did).  The connector is DB9-male.

Once you have it wired up, don't connect it to your tablet yet.  Connect USB to the Teensy, hook up a voltmeter across the output of the LM2577 module and adjust the trim pot until the output reads 9V.  Now you're ready to test it on the tablet.

One thing I've noticed is that if you turn off the tablet, you need to dis/reconnect the USB to get it to initialize again.  Likewise the tablet has to be on before connecting USB.

[bernard]

Nice ASCII ART !   

I see "R" and "T" twice on the Mini TTL-RS232 ?  Can you be more precise? (like a pin number or a distinguishing symbol?)

The trim pot is on the LM2577 device?

Tablet power should stay ON all the time. It will turn off as you turn off your laptop. Normally, we bypass the switch because we are injecting 5V in the middle of the circuit.

To allow such thing will require some code in WaxBee to detect that the tablet is no longer responding and trying to talk at lower serial speed, etc.

[Sicarius]

I see "R" and "T" twice on the Mini TTL-RS232 ?  Can you be more precise? (like a pin number or a distinguishing symbol?)

I had noted about the position of the caps but a picture is worth a thousand words.

The one on the right is positioned as in the drawing above.  These things are really small so the labeling isn't that great.

The trim pot is on the LM2577 device?

Correct.

[bernard]

Oooh ok. Now I understand better : these are breakout boards modules, not the naked chips!  For example, a LM2577 is a chip number. That is why I did not understand how a "pot" can be on a chip. I should have read better. Duh!