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Marketplace >> Wanted Items >> --WANTED-- circuit diagrams --WANTED--
(Message started by: Boris on Aug 30th, 2005, 12:15am)

Title: --WANTED-- circuit diagrams --WANTED--
Post by Boris on Aug 30th, 2005, 12:15am
This is probably the most wanted item in the Psioneers community:

the mainboard circuit diagram

Supposedly, the circuit diagrams came with the printed version of the technical manual, if there ever was one.

If someone should stumble over this treasure, please reply (;action=post;num=1125357349;title=Post+reply) or contact me immediately! :-*

Fame and Glory is to be Yours! ;)

Title: Re: --WANTED-- circuit diagrams --WANTED--
Post by theBot on Aug 26th, 2009, 9:47pm

This post has been here for four years, but still there is no result.

Fame & glory, anyone ?  

Title: Re: --WANTED-- circuit diagrams --WANTED--
Post by Geoff Rose on Aug 27th, 2009, 7:57am
Hi Folks.

I started drawing the schematic a while ago (gosh - was it four years ago?!!) but haven't managed to complete it due to other commitments (working away from home at the moment). I could have a look at what I have done so far and let you know.


Title: Re: --WANTED-- circuit diagrams --WANTED--
Post by starhawk on Mar 18th, 2013, 3:38pm
How many layers is the PCB? If it's just double-sided, I might try my hand at it... but the schematic will be hand-drawn! It's just how I roll...

Title: Re: --WANTED-- circuit diagrams --WANTED--
Post by Art on Jul 12th, 2018, 9:26am
2 layer board lol. How hard can it be?

Title: Re: --WANTED-- circuit diagrams --WANTED--
Post by Art on Jul 12th, 2018, 9:34am
I just checked the EEVBlog teardown, and it’s a main board with keyboard membrane on one side, and largely silicon on the other, and a daughterboard that is mainly thru-mount. Both are 2 layer. So what’s the problem? and more interestingly, if the community hasn’t managed to derive a schematic for it after all these years, what’s the same community going to do with a schematic that would justify reversing one?

it is also quite possible that by 2018, nobody cares :D

Title: Re: --WANTED-- circuit diagrams --WANTED--
Post by Mikesan on Jul 12th, 2018, 5:04pm
It takes time and a certain amount of knowledge and skill. Where vias exist underneath components like flat-packs, it means that the only practical way to be sure for most people (working out what a net of unknown components are from read values at various points is fun for some people and not others) is to remove the components and test the board with a multi-meter when it is bare.

I did send off a unit to a member, but he became too busy to take the task on, so I'll ask him if he'd get in touch with you via internal mail and maybe arrange to send it to you, if you can do this easily and would find the task rewarding. This unit doesn't work anymore, but did, so I *think* that the PCB is fine.

Of any use? Some people on here are extremely gifted and would probably do very interesting things with this information. They might not, but we won't know unless we give them the chance. Often people will baulk at buying a unit simply to tear it down at that is sometimes what is providing a barrier to further exploration.

It might, for example, be good if someone could simulate the entire hardware in something like KiCAD, or better (preferably free though...). Running such a simulation might help people answer their questions - "Is it a broken track?" "Capacitors?" etc, etc. Perhaps an emulator similar to Jaap's or Sora's could be integrated to produce a completely virtual copy of the machine - complete with real-world behaviour? What happens when the battery is actually too low? A short in a Datapak? Etc, etc, etc...

Title: Re: --WANTED-- circuit diagrams --WANTED--
Post by Art on Jul 12th, 2018, 5:49pm
I do not have an Organiser II, nor did I have any plans to buy one, but how is there a need to remove QFP packages from a two layer board? The only reason to send a via through the board is to connect the top layer to the underside, so any via seen from the bottom will be common to an IC pin on top, even if the top side of the via cannot be seen. The underside of the main board will be a keypad matrix arrangement, and little more... maybe some jumpers on the keypad side where required, but you might as well pretend they don’t exist, and measure from the top. Of course it’s still a bunch of time & work, but I don’t see any specific difficulty, even for a relatively serious electronics hobbyist. The hardware, I’m not sure about. They might have used a custom ASIC that you still don’t have by reversing a schematic. I’m pretty sure the 5mx does. I’m also pretty sure it is mostly stock, and that has to be a HD44780 LCD controller for sure.

Title: Re: --WANTED-- circuit diagrams --WANTED--
Post by Art on Jul 12th, 2018, 5:52pm
Why has interest in the PSION fallen away so hard while other retro platforms thrive today? That I do not understand at all. The Facebook Commodore Amiga group (for example) is 19k members strong, while the PSION user FB group is at about 140 members.

Title: Re: --WANTED-- circuit diagrams --WANTED--
Post by Art on Jul 12th, 2018, 6:09pm
Looking at it again, my best view of the guts is here:

I am not buying the difficulty. If you get the board back let me know.
I am in Australia, and will pay postage for the return.
Quite fair I think, since there is nothing in it for me.

I will check back in this forum from time to time.

Title: Re: --WANTED-- circuit diagrams --WANTED--
Post by Mikesan on Jul 12th, 2018, 6:12pm
There are no ASICs in the Organiser II, fortunately.  That came with the introduction if the SIBO OS found in the Series 3 and above units and their peripherals (the soap-on-a-rope 3Link contains one, for example).

There are vias there - pretty hard to escape having them, even with a moderately-pinned processor and other chips on a single board computer (the other board is an interface board for the packs, the top slot, charge pump and Datapaks and other things).

Why is there less interest?  Psion sold about 500,000 Organiser IIs, maybe a little more than that, but not much.  The Commodore Amiga had a MUCH bigger market.  Moreover, the Amiga was very graphics based, which the Organiser II is not and so that would have appealed to and inspired a much larger group of people.  Most people who had an Organiser II were pretty visionary, as opposed to those buying what was essentially a gaming machine back then.  That's just my take on it...

Title: Re: --WANTED-- circuit diagrams --WANTED--
Post by Mikesan on Jul 12th, 2018, 6:19pm
The person that I sent it to did find it difficult for various reasons, but fine, if you feel that you'd like a go, I'll 'internal mail' you with the internal contact details of the member and you can both sort that out if you want to, as I said earlier.

Title: Re: --WANTED-- circuit diagrams --WANTED--
Post by Art on Jul 13th, 2018, 5:43am
I see there are vias, just that for a two layer board with keypad on one side,
their only purpose can be to send signal from the keypad matrix, or jumpers perpendicular to lines on the top side.

Are you suggesting the hardware could be completely cloned?
Even if chips might be difficult to source now, etc. (I am pretty good at that).

What about ROM images and Copyright issues?
I suppose you could still buy ROM packs, but I assume it has something in it as stock.

In any case, the project is now promoted to the sufficient quantity of glory ;)
I see there are various models of Organiser II.
Which do you suggest?

Title: Re: --WANTED-- circuit diagrams --WANTED--
Post by Mikesan on Jul 13th, 2018, 11:59am
The LZ is the most practical - bigger memory, bigger screen, more built-in functions like Notes and better OPL.  It depends though, you lose the ability to display katakana (Japanese characters) which the XP could do - see my posts.

As for cloning, it might be.  See the emulator that the user 'Sora' made - that's based on a ROM image.  Psion don't even exist as a company anymore, so I doubt that they care much - even the later SIBO and EPOC machines have gone under the new ownership of Zebra (Motorola), who now focus on the modern corporate solutions only (their Workabout is a Windows machine now - OPL has gone).

Title: Re: --WANTED-- circuit diagrams --WANTED--
Post by starhawk on Jul 13th, 2018, 9:26pm
The problem is that the mainboard layout is CRAZY. I didn't run out of time -- I ran out of patience. A trace will go through three vias, hopping back and forth between sides each time, in the space of an inch-and-a-half -- or less! Whoever laid out the dang thing was either Circuit Merlin, absolutely bats***, both, or a rather gifted Italian chef, because the layout resembles nothing so much as a plate of electronic spaghetti.

I tried to use a straight pin (the vias are juuuust big enough to poke one through) to keep track of what went where how, but even that wasn't enough to keep me straight. So I said eff it.

What I need to do, really, is heatgun all the chips off, and scan both sides of the mainboard. then bring them into an image editor (something like Photoshop), mirror one so they're facing the same way, overlay them, and reduce the opacity of one -- that way all the vias line up and the traces connect and I can effectively see both sides of the board at once. However, I've not had sufficient motivation to do that (I have a form of autism, and that's one of the effects).

Further, while there are indeed technically no ASICs per se, there is a PAL -- programmable array logic, an early precursor to the FPGA -- that someone's going to have to reverse engineer or get the programming for, if we want the complete picture.

Title: Re: --WANTED-- circuit diagrams --WANTED--
Post by Art on Jul 17th, 2018, 6:07am
I would buy my own if it were stock parts, but the PAL kills it for me.
Essentially a PGA, but it is not guaranteed to be input in one side, truth table out the other.
Any use of registers (flip-flops) can make reversing it range from difficult to nearly impossible.
That definitely kills it for me.
I have hardware with PALs I would spend the time with before this.

I think you are overcomplicating the keypad PCB.
Did you check that the rows and columns of the keypad matrix do not simply end up at at IC pins all in a row?
Then it does not really matter how they found their way there through the PCB.
The LCD controller can also be largely ignored, sine the controller would be part of the LCD module now,
and you are only really interested in communication between the (assume HD44780) controller and the rest of the board.

Removed contractions in my words to avoid that thing the forum is doing.

Title: Re: --WANTED-- circuit diagrams --WANTED--
Post by starhawk on Jul 17th, 2018, 4:50pm
The part is a Mullard PCF0330 in my broken (for reverse-engineering) Org2.

I had assumed it was a PAL with fixed inputs and outputs and not a lot of capability in between, but I'm wrong. Per datasheet, this is a full PGA sort of thing.

The LCD controller is indeed an HD44780A, and the driver chip is an HD44100H. In fact, the Mullard PGA is the only chip I can find that's not made by Hitachi...

Except for the labyrinthine traces (and oh boy are they), the machine is fairly simple -- there are only eight chips, one of which is an LM324 on the power supply.

The others are the LCD controller and driver, the CPU, the PGA, two RAMs, and a ROM. There is an unused footprint for a 2nd ROM, interestingly.

Title: Re: --WANTED-- circuit diagrams --WANTED--
Post by starhawk on Jul 17th, 2018, 8:31pm
Oh right. There is one further issue with reverse-engineering the Org2. It appears some corners were cut in the most unlikeliest of places, presumably because the devices were maybe a dollar too expensive or something. I'm really not sure why, actually -- but the PSION Organizer II is one of two places (the other being the keyboard for a Tiger Electronics Wheel-of-Fortune electronic game, where cutting corners until there's hardly anything left is quite reasonably expected) that I have ever seen what are called "carbon deposition resistors".

If you open a PSION, working or otherwise, and you look at the back of the mainboard, you will see several SMT-resistor-sized black "pads". What PSION has done there is to print carbon-composition resistor material directly onto the PCB. This has two effects -- one, it makes that component that much cheaper to 'put down' -- and two, it makes it utterly impossible to determine the actual resistance of that part without literally cutting a chunk out of the board.

Remember, passives cannot be accurately measured in-circuit, because of current leakage into the rest of the circuit... and if you can't remove the part without destroying it... yeeeaaahhh that's gonna be an issue.

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