Keep taking the tablets

[John Rumm]

Quick little electronics hack project for those interested:

(early draft - so typos may abound!)

[Andy Burns]

My wacom is a USB version, but same as you discovered, using a tablet didn't turn me from a scrawler into an artist, so it sits in the bottom of a drawer somewhere.

[newshound]

Same experience as Andy.

But your project *really* makes me feel inadequate: decades ago I used to do something like the equivalent of stuff like that. I remember soldering a rotary switch to the jumpers of a PDP-8 board that cost more than a year's salary. Carefully.

And Vero wire! That really takes me back. I had a contractor friend who had a home-worker who could put 1500 wires on a prototype wire-wrap board without a single mistake.

[jkn]

Thanks John, I can see me wanting to do a project like that at some point. I think I have seen the Teensy project before but good to have a link to it.

Cheers Jon N

[T i m]

Nice one. ;-)

Cheers, T i m

[Fredxx]

I use a Belkin RS232 to USB converter as you can still get drivers for these.

If Windows 10 sees a USB COM port it will naturally use its own drivers. Prior to Windows 10 COM ports were a nightmare, hence the FTDI debacle.

It might be worth plugging in your old converters into a Windows 10 machine to see if they are recognised before binning them.

The MC145406 changes from TTL levels to RS232 levels. You can get very cheap TTL level RS232 USB converters though they don't always come with all the signals I believe you might need.

Nice project.

[Dave Plowman (News]

Many aftermarket car ECUs (MegaSquirt, etc) have an RS 232 port. And virtually no laptops (used for tuning) have them these days. I've not had a problem with my USB to serial adaptor on changing to Win10. Although there are some around that don't work with MS at all - a different chipset.

[Fredxx]

I'm guessing the ones that don't work don't conform to the USB VCM USB protocols and have a bespoke driver.

[John Rumm]

Yup the RS232 to USB converters work fine (ish - I have had some chipsets that worked and some that did not in the past), but the Wacom drivers that do serial tablets don't seem to want to play anymore, and the USB drivers dont expect to see a serial tablet on USB. So getting the USB interface is only part of the problem - you also need to make the tablet appear to the windows driver as a more recent USB model.

Was not planning to bin them... I have other things that can talk RS232.

I would suggest a Max232 if you want a simple to use driver, since it will run off a single sided 5V supply.

Well I had had the bits sat there for a couple of months - just needed an appropriately shaped tuit! So thought I would give it a try.

ISTR there is another much smaller Wacom floating about - I might have a go at that next, since I have another Teensy.

[John Rumm]

:-)

Yup I remember a certain "pucker" moment making mods on a double eurocard sized 386 processor board... with all milspec components, a deep multi layer board, and this was in 1988 when even the retail 386 was silly money!

(IIRC the card was worth £20K in 1988 money!)

I remember working on a prototype CPU card that someone had wired up with Dagewire - It was an enamelled copper wire based prototype system that used little IDC terminals on the bottom of a matrix board. It was fine at first, until you had to make changes, and it becomes progressively less reliable with time! It made doing hardware software integration fun as you always had to work out if the software is wrong, the hardware design wrong, the build wrong, or do you just have yet another loose connection!

(vero wire would have probably been better!)

[Dave Plowman (News]

IIRC from the MegaSquirt forum, it is to do with the 'make' of chipset in the adaptor. I'll look up the name of the one that seems to work best if you want.

I do have a USB to serial adaptor that won't work with MS - but Windows doesn't seem to object to it.

[Jeff Layman]

I've got an old Wacom Bamboo tablet which I used to use with my XP desktop. Unfortunately, I changed to a laptop in 2009, and, like yours, the Wacom remains disused in a cupboard.

Now if John wants to work out how to use the Wacom's stylus with my laptop's touchpad, I'm all ears. And I'm all sticky fingers too, as when I dug the stylus out of the bag it's been in for 8 years the whole surface was gooey and sticky. Some isopropanol removed it.

[Adrian Caspersz]

Fond memories of long nights of solderless wire wrapping, 8 bit DIL CPUs on verocards. 6809 style. Don't believe anyone does that anymore :)

For giggles I have a few 486SX25 CPUs stashed. I've wondered if I should dig out the gear and wire something up for old times sake of seeing homebrewed clock cycles again.

[Fredxx]

I now use my own micro to do the conversion and keep the signals in the TTL domain rather than the inverted +/-9V

The adaptor might not have all the signals you use. Apart from the Rx and Tx signals there a number of others used for handshakes. For some applications they can be repurposed to reset or program your unit.

Not all adapters are the same and I suppose can be the reversed gender. The fact it is recognised by windows means the protocol conforms to the USB VCP/COM port rules. The hardware side might not conform to standard RS232 or relies on a specialist driver to drive these signals appropriately.

[Fredxx]

I'm surprised this is an issue where you're using Windows 10?

The Windows drivers should provide a COM port and any application should be oblivious to whether its talking directly to a serial COM port or a USB device emulating a COM port.

Two of the signals sourced from the MC145406 are grounded. Why, does this cause any issues? I presume these would normally be handshaking lines used to buffer data.

[John Rumm]

I quite like messing about with old 8 and early 16 bit stuff like that, but find it harder to get nostalgic about 486 era stuff - not sure why.

Perhaps because dealing with that many pins for so little reward seems like hard work! :-)

[John Rumm]

It does. But that only gets you at best half way there. Win 10 may even recognise a tablet as a HID and let you move the mouse. However to go further and gain pressure and tilt sensitivity, you need the Wacom driver. And the ones that recognise serial tablets don't work on win 10 (or 64 bit windows in general).

The wacom USB drivers can run on Win 10, but then they expect the USB device to identify as a wacom device and not a generic com port.

Yup many of the easier to use ICs like the MAX232 et al only have enough paths to handle a couple of inputs and outputs. Certainly enough for basic async comms, but not enough for some of the more esoteric implementations of RS232. The MC14506 has enough paths to handle tx, rx, rts, cts, dtr, dcd for fuller spec interfaces - although you have to provide your own negative power rail.

That was just belt and braces - the serial interface did bring DTR and RTS through to the line driver, so it was possible (although probably unlikely) they were used in the tablet firmware - so thought it better not to leave them floating.

[gareth evans]

try the NG alt.folklore.computers