Odroid N2+ laptop.

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Re: Odroid N2+ laptop.

Post by mctom »

Meanwhile I got a gigabit 8-port switch for some $7 with shipping.
It came with 5V wall wart, but I think it may work with any reasonable voltage - doesn't matter as my cluster nodes need 5V as well.

It is bigger than I expected, and requires a heatsink. It measures 23mm height in the highest point.
The rightmost inch of the board may be cut off, it contains only the paranoid LC filtering of input voltage. That doesn't change much in my application, but an observation worth noting if I was just millimeters away from a perfect fit.

I don't like that heatsink.

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Re: Odroid N2+ laptop.

Post by mad_ady »

The heatsink may be reduced in size if you downgrade to 100Mbps/or keep traffic low between nodes. I expect it gets hot under throughput. Try flooding a port with broadcast traffic to make it sweat.
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mctom (Fri Dec 10, 2021 3:57 am)

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Re: Odroid N2+ laptop.

Post by mctom »

Hey I haven't thought about that. I'll SmartPower3 this thing and see if this heatsink is really necessary in the first place.
May be necessary only in Korea, like a fan on on N2+ :lol:

As the last resort I'll transfer that heat to the chassis somehow. I don't want to count on heat dissipation into the air in a water tight space.
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Re: Odroid N2+ laptop.

Post by notime2d8 »

I saw one of these online and it made me think of this thread. It seems like it'll make a good base for a project. Symbol VC5090 ~$76 USD on ebay right now.
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Re: Odroid N2+ laptop.

Post by mctom »

That quite a lot for this. I'd wait or seek for a $30 deal on something similar.

Reusing that keyboard may be really tricky, as long as you have skills and patience to reverse engineer it, and possibly develop a converter (wouldn't count on anything "standard").
In case of my military laptop, I haven't looked into that just yet, but I hope this will be a PS/2 keyboard and mouse. After all it did work with x86 computer that accepted such input devices.

The display may also have a weird, or plain unknown interface. Again, in case of a laptop I assumed LVDS and it indeed seems to be the case. For monochromatic LCD or whatever is in there, I wouldn't be that optimistic.

I'm not saying it can't be done, just be mindful about the upcoming challenges. :)
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Re: Odroid N2+ laptop.

Post by mctom »

I have just sold the laptop guts on the auction - some guy must be passionate about that era of computing.
I bought the laptop for $18 and sold the guts for $30. I'm good at this!
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Re: Odroid N2+ laptop.

Post by mad_ady »

Throw him a little discount if he tells you how he fixed it

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Re: Odroid N2+ laptop.

Post by mctom »

I'm pretty sure it will work for him, as he was after just the SBC, and asked for all the remaining parts just because I offered them for free.
Without the mysterious bundle of wires coming from a hardware key reader, it might actually work better. ;)

EDIT:
The guy who bought the laptop guts is super happy. He wrote me everything works fine, and thanks to the CF adapter he has already installed Windows 98, even connected USB keyboard to it.
He also says his partner is happy he kept his retro computing hobby smaller than yet another full tower PC.
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Re: Odroid N2+ laptop.

Post by mctom »

Finally, a bit of spare time to reveal the very last secrets of the military terminal.

Disassembling a display half is straightforward, there are 12 screws and the thing pops open.
I think this might have been tampered with, judging by less than ideal gasket alignment.
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Aside from the obvious display panel at the center, there are two PCAs. The one on the right is an LCD backlight inverter, accepting 5 wires and with what appears to be two independent outputs. Makes a lot of sense for two CCFLs within the display.
Right next to this board, two contacts of iButton socket can be seen, essentially a 1-Wire interface.

The display itself doesn't seem to be special in any way. 10.4" 800x600 display, antiglare, antireflection, hard coating. 6-bit CMOS interface, which is a bit of a surprise. I was expecting LVDS input!
I expect this display to be the major power guzzler in the whole build, but well, I'd rather leave that alone than trying to fit anything else in there.
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And the last board that I predicted must be here.
Half of the board is unpopulated an there are no hints what could that have been used for.

A thick bundle of colorful wires comes straight from the main chamber of the machine, and used to be connected to custom "motherboard".
White/purple wires are connected straight to iButton socket.
Another five Jamaica-themed wires go to the inverter.
Finally, a dual brown/orange pair, presumably to power TFT logic. Doubled wires give a hint it must consume a lot of power, but why would a display logic need so much?
I just noticed that the TFT assembly has been tampered with and has been put back slightly incorrectly. Certainly that didn't leave a Japanese factory.
So I suspect they've put a heater inside.
It suddenly became too dark to work on disassembly, so I'll verify it tomorrow.

On the far left of the board, there are three chips are clearly visible:
- Standard 4051 8-to-1 analog multiplexer that selects between one of 5 resistors next to it. I suspect it's for backlight control, as the resistors are being connected between two wires going to backlight inverter.
- DS1620, a well known temperature sensor,
- SI9945A, a dual N-channel MOSFET, with both devices connected in parallel. They act as a low side switch for orange/brown supply (Display logic / heater?).

And there is a TQFP chip with a sticker on it to govern all that. It was easy enough to guess it's another AT90 MCU, but I checked just to be sure. ;) And 8-pin header that I've seen on other boards, I assume it's for programming.
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And finally, there is a tiny board I didn't notice before. It acts as a breakout of the second wire bundle that goes to main chamber. Clearly this parses video signal. Only 8 wires out of 10 are in use. Indeed DS90CF364 has only four LVDS inputs.
To recap, the other end of this cable is soldered into a small shim board that was directly connected to P5 SBC, and contained a complementary LVDS transmitter.

I think this solves a mystery that I tried to work out last time:
mctom wrote:
Sun Dec 05, 2021 4:53 am
For any reason they had to design a shim that goes between SBC and motherboard, to capture display data. There is a dedicated footprint for LCD, but unpopulated. I think they might have changed the LCD type at some point,
Not quite. I think they ran into issues with direct CMOS/TTL signaling, picking up too much noise. So they opted for LVDS (Differential) transmission instead. Shim was conceived to shorten the unbalanced signal path.
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Re: Odroid N2+ laptop.

Post by rooted »

How are you going to drive the display? LVDS to HDMI converter I'm guessing, a bit expensive aren't they?

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Re: Odroid N2+ laptop.

Post by mctom »

Well if there is no Odroid with LVDS output around the corner.. :D

I see a few options:
- I know RasPis can output raw display data straight to GPIO (they call it DPI - Display Parallel Interface?). If something similar was possible on any Odroid, it would be very cool.
- HDMI to LVDS converter. There are some on Aliexpress under $25, just have to be careful about selecting a generic or hackable one, not for a predefined display type.
- Use preexisting SPI display driver and translating SPI to LVDS (It's a terminal, I can sacrifice color palette or refresh rate).
- Write my own display driver that bitbangs single-ended display data to GPIOs. I mean, how hard could it be to write a kernel driver :lol:

Most of these ideas assume designing a custom motherboard where the existing CMOS-LVDS shim would fit to. Not a problem, I'll have to design some circuitry anyway.

I think I'll end up with HDMI to LVDS to save time and be more future proof... But more ideas or comments are very welcome!

It puzzles me why there are no USB3 - LVDS converters yet.
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Re: Odroid N2+ laptop.

Post by rooted »

The only problem with LVDS to HDMI is most are for a specific resolution and if lucky may have some dip switch for two resolutions.

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Re: Odroid N2+ laptop.

Post by mctom »

Hm, yeah, I remember those D-SUB - LVDS converters had a dunkton of jumpers to set resolution and color depth. I assumed these were gone as HDMI can negotiate preferred resolution, based on display's EDID.
However that display probably predates any display identification protocols.

I think I could use HDMI - "VGA" adapter, then "VGA" to LVDS that I already own, and then yet another board to interface it with the wires that I have, but clearly that's far from ideal.. Not in terms of weight, but the general clutter I'd rather avoid.
Since I do have (almost) all these components I may try and see if it's working in the first place, and then try to reduce it somehow.

I had some reading about Linux video drivers and nope, I'm not going there.

But before all that - I'll have to reverse engineer that gay bundle of wires and apply correct voltages in the first place. I guess I was a bit too hasty selling off these guts, but fortunately I do have photos and a phone number of the buyer.
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Re: Odroid N2+ laptop.

Post by mctom »

I tried to figure out the keyboard.

So, it seems two pins send out PS/2 compatible data on each key press. The problem is - no matter what key I press, it's always 0x4A, which corresponds to keypad "-". For some buttons, it sends the same code two or three times in a row.
Incidentally, keypad "-" button is on the very corner of the matrix, so may be internally coded as "the first one" or something.

PS/2 has separate codes for button press and release, so I'd expect at least something different on button release, but nope, it's also 0x4A. That's why I don't think it is a hardware failure. Matrix muxes seem to do their thing and all.
Oh, and Caps lock light worked, I think? I'm not so sure now.

I think this keyboards wants a hardware key to work correctly. That's why I couldn't enter BIOS Setup on this machine, by the way.

Moreover, on one of the pins it sends a binary string "(ones)010110010(ones)", every second. Each bit lasts 50us. I think this further supports hardware key theory.

The keyboard is driven by AT89S8252. Not only do I lack any experience with this architecture, I don't think I'd be able to simply download its flash contents :roll:.
And even if I did, I'd have to rebuild the whole hardware key infrastructure and so on..

Perhaps the simplest solution would be to fit a modern Atmega in its place (I hope there is at least one pin compatible model out there!), and reimplement the keyboard from scratch. I really don't see other options.

EDIT: Sending two or three codes in a row was a feature of upgraded PS/2 code set. 0x4A corresponds to "/" key in it.
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Re: Odroid N2+ laptop.

Post by mctom »

Isn't that the best to have an eccentric Swiss uncle whose ex wife has decided to get rid of his old stuff? :D
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oh, my... Cassiopeia doesn't look like much on that photo, but it is a beast of a machine, 25mm thick and some 19cm long. I imagine there must be some 8-16mm of space just for guts.
Almost could fit an N2 without connectors :D

But I think that one should wait for later, too many computers to build already. With such old display (4 shades of grey 640x240, blue backlight, resistive touch) I can't imagine it for any multimedia purposes, or even GUI. I think its destiny will be STM32 based Wi-Fi enabled portable terminal.
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