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Old 02-03-2013, 04:43 PM   #1
euphy
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Odd components on mini PCB and serial link

Hello everyone, I got a kobo mini a couple of weeks ago with the intention of using it as the display for an alarm clock. It'll be connected to other stuff eventually, and run a small program that does display, handles input and triggers other bits of kit (lamp, buzzer, radio etc).

I've used the great hacking guides here on the forum to telnet in - thank you all very much for posting those. I've also opened it up to solder in a header to the serial pins. Does anybody have any experience of reading / writing info from those pins? Does the serial port show up by default in the OS, or will I have to do some tinkering to get it visible?

The other this was that looking at the PCB, the outside edge is lined with what appear to be LEDs. The top and right edge have clear packages and are labelled D<number>, and the bottom and left edge are dark, like IR receivers of some sort, and labelled Q<number>.







They are definitely optical components but I can't see what they do. The case has a series of scalloped lenses inside it, that match up to the components. I can't see anything similar in any teardown pics of other e-ink devices, so I'm guessing it's something to do with the touch sensors? Puzzled. Any ideas? I'm just curious really.

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Old 02-04-2013, 03:26 AM   #2
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I suspect they're the infrared emitters and receivers that do the touch detection.
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Old 02-04-2013, 04:46 AM   #3
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Yes, pdurrant is right, Mini, Touch and Glo all use infrared touch; so one side emits the infrared light and the other one receives it. Let us know how it went with the serial access! I think you will need an adapter to use 1.8v signals (or maybe 3.3v), you surely can't directly connect those pads to the serial port of a pc or you'll fry the board.
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Old 02-04-2013, 07:15 AM   #4
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Aha, thanks, I've never seen IR touch detection before, only the resistive stuff with the four wires. Interesting! Is it a matter of breaking direct beams, or something more sophisticated than that? The "resolution" of the touch seems like it must be.

Yes I haven't probed the serial port yet but I guessed 3.3v. I'll check and hook an arduino up to it and see if anything is occurring that I can get into. I have read a blog that reported that the linux console was being piped out to it at 115200 baud. Not quite sure what form it'll take, but I'll have a dig.

I want to be able to use the port to send commands to trigger a dimmer (probably via an arduino-a-like), a music player/radio and to poll for input from physical buttons (big snooze button on the top). Pi running the show and using the kobo as simply an interface is another option.


cheers!
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Old 02-04-2013, 09:04 PM   #5
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I think the IR Touch hardware is based on a chip made by Neonode, so you might want to see which chip corresponds to their naming convention/numbering and check out a datasheet from them. I'm guessing you'll probably find a very good example of their basic implementation.

Based on the spacing between sensors and the apparent resolution vs. the number of discrete sensor pairs I'd hazard a guess that they might even detect if you're blocking adjacent sensors on the same axis and interpolate to provide higher resolution.
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Old 02-05-2013, 07:09 AM   #6
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Speaking of the IR touch screen, last night I tried viewing the screen of my Glo with an IR camera to try to work out the polling rate, as sometimes the screen is really sensitive, and other times it barely reacts at all. I wanted to check if the emitters were running constantly at a set rate or if there was some sort of energy saving slow poll rate that is ramped up when it detects a touch. Try as I might, I couldn't detect any IR light from the inside lip of the Glo, even though I know it's there. Does anyone know the wavelength of the LED's? as I couldn't see anything up to around 900 nanometers.
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Old 02-05-2013, 07:16 PM   #7
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Quote:
Originally Posted by giorgio130 View Post
Let us know how it went with the serial access! I think you will need an adapter to use 1.8v signals (or maybe 3.3v), you surely can't directly connect those pads to the serial port of a pc or you'll fry the board.
That was easier than I expected, I used a usb-to-ttl serial port adapter and hooked the rx, tx and gnd of the kobo's serial port up to the tx, rx and ground on the adapter. The adapter itself has an FTDI chip in it that shows up on my pc as a virtual com port (COM4). Then used putty to initiate a serial connection on COM4 at 115200 baud, and hay presto, a fully functional terminal console.



Now, I like this because I don't have to worry about the USB host/non-host, bus powering situation. I can have an arduino or somesuch watching the kobo's serial port, looking for signals to dim lights or do other stuff. Not sure about the audio - that might call for something with more peripherals, and if I'm using that then the serial hack might be a bit unnecessary because the kobo will be back to just being a pretty display.
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Old 02-19-2013, 11:21 AM   #8
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I'd like to get a serial connection working on my Glo, but I'm completely clueless about this sort of thing.

What would be the best way to get started learning what I need to learn to setup a serial link?
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Old 02-22-2013, 04:26 AM   #9
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Hi Kevin, first of all I want to say thanks for the work you've done, and written up about getting pygame etc running on the Kobo - dead useful and very encouraging.

The kobo mini is the only one I've used, and that has a hardware serial port present on the PCB itself (bottom right corner of the PCB in the middle pic in my original post). The kobo touch has the same port, so I assume the glo does too, but I can't find a teardown of it to look at.

All I did was solder some sockets into those holes. The pins exposed are GND, RX, TX and +3.3V, of which you need to connect up only GND, RX, TX. So that gets you a TTL serial port which might be useful if you're interfacing with another TTL thing, like an arduino or something. But for connecting to a computer I needed a TTL-to-USB converter.

I used one of these
http://www.elecfreaks.com/store/ardu...pter-p-16.html because I wanted the other features on it,
but there's lots of different kinds (http://shop.moderndevice.com/products/usb-bub), including ones that are built into the cable (http://www.tronisoft.com/prod.php?id=2472). Just as long as it's a 3.3v version rather than a 5v version. Most of the PCB-ish ones can be switched to 3.3 or 5v with a switch or jumper.

So use jumper wires (http://www.elecfreaks.com/store/1-pi...pcs-p-165.html) to connect the transmit (TX) of the kobo to the receive (RX) of the usb adapter, the kobo RX to the adapter TX, and the kobo GND to the adapter GND. Don't need to worry about the kobo supply (3.3v) since the usb adapter is already powered over the usb bus.

The usb device (cable, bub, adapter whatever it is) shows up as a virtual com port on the PC, and I used PuTTY to connect to it. PuTTY has a "serial" method of connection, and I just used the default settings I think, but I can check that later if you like.

My problem is that the root terminal that is exposed this way (which is the same as the one that is exposed over the wifi telnet thing) is exactly that - the root terminal. So all the activity on the kobo is being reported over it, so there's a lot of noise. For my purpose, I want a fairly clean channel that I can pipe commands over, that isn't going to be interrupted by the kobo system's messages every now and then. So I think what I might try to do is get the usb-ethernet set up instead, and ssh between the kobo and the pi. I couldn't get the usb-ethernet working last time I tried, so it's time to try again.

Maybe that's helpful! Anything you want me to test, just ask.

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Old 02-22-2013, 10:41 AM   #10
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Thanks for the great writeup, euphy. Getting all the Kobo's activity is exactly why I want to setup a serial connection. Someday I'm planning on trying to port Android to the Kobo.

There seems to be two serial ports on my Glo. One is at the upper-right corner of the board and labeled "J1", and the other is near the bottom-left and marked "J2".
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I honestly have no soldering experience. Would it be best to get a little experience before tackling my Glo? I'm assuming there's a least a little risk involved in soldering a serial connection on the Kobo.

Thanks again.
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Old 02-22-2013, 06:29 PM   #11
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Hi, no idea why there'd be two - I'd assumed the glo was just a regular touch with a fancier panel - I can't think why you'd want two. I'm guessing at least one of them will give you the root terminal access though. You could test which one by manually holding your pins, or sockets onto the metal of them to check, before soldering.

Soldering isn't hard, but there is a bit of a knack to it. Overheating the board is usually my biggest problem in things like this - if you leave the heat on for too long then sometimes the copper traces lift off the board, and they're next to impossible to make secure and reliable after that. On the other hand, if you destroy your serial port headers then you've not lost much since you aren't using them anyway. You'd probably struggle to do any damage beyond mangling the physical traces.

But it is bulky - even the most compact connector will stick out of the case and be sharp and uncomfortable - if you plan on using the glo as a reader.

I can see why having a hardware serial port would be useful for a change as big as a new OS - I guess it means you don't have to worry about having usb drivers in place right away? Or is there something else that is missing from the usb implementation of the serial port/ethernet?

(and the serial parameters are 115200 8 N 1 - I re-found this on http://blog.ringerc.id.au/2011/01/se...serial-on.html)


cheers!
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Old 02-26-2013, 03:57 PM   #12
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Yeah, I'd like to have the serial connection so I don't have to worry about usb stuff. However, I do use my Glo for reading, so the pins sticking out would be a problem.

I read over in the kindle dev forum that some people, instead of soldering, have taped the serial connectors on their kindle for a temporary connection. I'm thinking that I'll try doing that.
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Old 03-02-2013, 04:34 PM   #13
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I've been looking at this, and with a right angle connector I reckon it could easily be flush with the case. With the snap-on top cover that the mini has (I don't know if the glo has those things), I think it could be covered up completely.



I'll give it a shot later and report back.
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Old 03-07-2013, 06:16 AM   #14
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I wonder if you could use one of these....



That is basically a serial interface that broadcasts via bluetooth. You would solder the serial header on the kobo to the Tx/Rx/Vcc/Gnd of the module - then find somewhere to stick it under back cover.

You would then have serial access via bluetooth.

This assumes that the kobo itself puts out Vcc on the serial header. If not we'd need to tap off another point.

You'd also obviously decrease battery life but I suppose you could fit some kind of switch inline on Vcc.... hmmm

Last edited by Katch; 03-07-2013 at 06:19 AM.
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Old 03-07-2013, 06:21 PM   #15
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I decided to order this TTL to USB adapter, and it just arrived today. I followed euphy's directions on connecting the adapter to the Kobo, and it's working perfectly so far. Thanks, euphy!

I didn't notice it before, but the Glo actually has three serial ports. The only one I've been able to get anything out of is J3, however.
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