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Casio A10/A11/NEC Mobilepro connector pinout and rechargeable batteries

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astrosynthesist Page Icon Posted 2020-01-13 4:43 AM
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Factorite (Junior)

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Hi all, decided to take a look inside the serial/power adapter for the Casio today in the hopes of learning the pinout for the connectors - those of you who don't have a power supply or a serial cable, hopefully you can use this information to make your own. I do not have a part number for the connector sadly, so right now it seems like at bare minimum you need the expansion unit or dock to get a connector that will fit your HPC. The good news is it is very easy to solder a power/serial cable onto the connector!

RS232:

I have not investigated which pin is TX/RX/DTR/CTS/etc yet, but I will do that soon. Underneath my thumb () are really nice little solder pads that are very convenient.

Power:


In summary:
|  1  |  2  |  3  |  4  |  5  |  6  |  7  |  8  |  9  | 10  | 11  | 12  | 13  | 14  | 15  | 16  | 
| NC  | NC  | GND | NC  |SENS?| +5V | +5V | GND | NC  | SER | SER | SER | SER | SER | SER | GND |


I also disassembled my OEM NiMH battery pack. It uses two 4/5AA NiMH cells in series with no balancing circuitry, with some weird connections on a tiny fpcb each end. I am planning to reverse engineer what gets connected where, because at first glance it appears that all you need to make your own (superior to factory) NiMH pack is to take a standard AA pack and short out two contacts on one end. More will follow soon.

EDIT: Added connector pinout images and pinout diagram

Edited by astrosynthesist 2020-01-13 5:10 AM
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C:Amie Page Icon Posted 2020-01-13 2:41 PM
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Is there enough room to do a Li conversion?
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astrosynthesist Page Icon Posted 2020-01-13 2:49 PM
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Factorite (Junior)

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The cells have the same diameter as AA batteries and are 4.0 - 4.2mm long. This is because the end contacts are rather fat in comparison to the standard AA battery bay. There is also a screw post directly in the middle of the pack which makes cramming AAs into the rechargeable case difficult. So if there exists a 4/5 AA size Li-ion battery yes possibly but the big problem is you need to step down the voltage of Li-ion cells to be compatible with 1.5V or 1.2V cells. The ones on the market today in fact do this. Beneath the button on the positive terminal of Li-ion AA batteries is a little buck convertor as I recall.

The big problem with Li-ion conversions is that the NiMH charge circuit is built into the Casio, so if you were to throw lithium cells in there they would be liable to explode unless you blocked the charge circuit with a diode.

So then the two solutions here would be either:
Use Lithium-ion AA batteries in the standard AA battery bay, and charge them yourself

or

Take advantage of modern NiMH AA technology and try and make a way to adapt a non-rechargeable battery pack into a rechargeable one.

I personally think in this case the latter is more feasible. I will append pictures of the battery configuration in a moment above.
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astrosynthesist Page Icon Posted 2020-01-13 3:05 PM
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Didn't realize there was a time limit on post editing.

Battery assembly structure:


Oops, forgot which side was which.
Positive (I think) end:


Negative (I think) end:



Edited by astrosynthesist 2020-01-13 3:07 PM
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C:Amie Page Icon Posted 2020-01-13 3:27 PM
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My intention in 'is there room' was 'is there room to replace the charge circuit'?
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astrosynthesist Page Icon Posted 2020-01-13 3:32 PM
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Ah, well, there should be clearance in the case to be able to stick a basic Li-ion charger in. The problem with this particular design is that it is entirely single-board, with the exception of the ROM of course.




(borrowed from the following Russian-language page: https://m.habr.com/en/post/212849/)

So in theory it is possible to de-solder the battery wires and trace the power input and tack onto that and use a lithium battery charge circuit.
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C:Amie Page Icon Posted 2020-01-13 3:49 PM
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Could be a nice little open source circuit design project, if you have the time and skill to draw it up?
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astrosynthesist Page Icon Posted 2020-01-13 4:19 PM
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Maybe - but my inclination personally leans towards using modern NiMH technology as high capacity cells today will vastly out-perform the old rechargeable packs, and the charge circuit is already there and correct, AND voltage sensing will work.

I will do some poking around though and if I do find a feasible way to do a lithium cell upgrade I will post about it. Generally speaking for me I am more inclined to find an off-the-shelf pico-lithium charger than design my own board for a project like this. The biggest lithium cell hurdle will be balancing as to the best of my knowledge it is more critical for lithium cells than it is for NiMH cells. In either case since the discharge characteristics of lithium cells is very different from NiMH cells, I am not certain if the battery level sensing will work with them. Not a big deal.

It is worth investigating these new-fangled AA Lithium batteries:
https://www.amazon.com/TENAVOLTS-Rechargeable-Batteries-rechargeable...
https://www.reddit.com/r/AAMasterRace/comments/chzxhv/review_teardow...

They have charge circuits built-in that require a 5V input... and my Casio's power supply just so happens to be 5V. So if I can devise a means to apply 5V in parallel to each cell when charging and then have the cells in series when discharging that could be a very useful nearly drop-in solution.
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Rich Hawley Page Icon Posted 2020-01-13 8:11 PM
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Many lithium ion batteries today come with anti-overcharging circuitry built onto the battery, normally a simple micro pc board stuck onto the anode end of the battery.

You might consider finding a contact on the motherboard that will provide you with the voltage needed to charge a couple of these type cells independently and then cut the native trace the feeds the batteries under normal usage.
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astrosynthesist Page Icon Posted 2020-01-14 5:33 AM
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Okay, some progress on the battery front.
I seem to have successfully made my own NiMH replacement pack using an Alkaline holder.
Deconstructing the OEM battery pack told me the following:
Negative terminals are shorted together, positive terminal, only the small one is apparently connected to the battery proper.
So then, why not use 2 NiMH AA cells and make my own janky contacts?
Behold the majesty (note that it is very easy to remove the original contacts without destroying them. Use a fine flathead screwdriver and wedge it under each side of the little flaps on top of the contact):
Positive side:



Negative side:



I used stripped solid core wire to make the contacts, and subsequently wrapped the outside with aluminum foil. It was a tight squeeze fitting it in the battery bay, but my charger LED is on!
I put really crummy old flat NiMH batts in there for now, hit or miss if they will actually work when all is said and done. But I have some new amazon basics batteries lying around somewhere...

I also noted something interesting. The charger brick and the power brick are separate; the power brick can plug into either the port replicator (not the dock) or the charger brick and it supplies +5V. The Charger brick has printed on it that it has a 5V power input and a 3.7V power output. So it looks like the NiMH charging circuitry is contained inside the charger brick. That explains why there is an extra wire on the "Charger" side of the port replicator (see pictures above). I will hopefully trace out all the pins before I go to sleep tonight. This potentially makes things a little more difficult trying to make an effective drop-in lithium battery. If I can find an always-5V-point inside the charge circuitry then I have designed a simple circuit that would allow for charging of the lithium ion AAs I was talking about earlier. The rough sketch of the charge circuit for the lithium ion AA batteries is below.


Edited by astrosynthesist 2020-01-14 5:37 AM
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astrosynthesist Page Icon Posted 2020-01-14 8:31 AM
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Expansion connector pinout:
|  1  |  2  |  3  |  4  |  5  |  6  |  7  |  8  |  9  | 10  | 11  | 12  | 13  | 14  |   15    | 16  |  
| NC  | NC  | GND | BAT | BAT | +5V | +5V | GND | NC  | CTS | DSR | RxD | TxD | RTS | DCD/DTR | GND |
RS232 to expansion by pin number (because I don't trust myself to label the pins correctly) (pin 1 top right as normal for DCE)
|  1  |  2  |  3  |  4  |  5  |  6  |  7  |  8  |  9  | 
| 15  | 13  | 12  | 11  | GND | 15  | 10  | 14  | NC  |


So the charger works but for some reason the HPC won't turn on... strange. Will investigate further. Pin 5 BAT is direct connection to battery voltage. When charging it goes up to 3.2V. (Pin 4 is internally connected to BAT as well)

Also on the system board it appears as though pins 1, 2, and 9 go somewhere, although 9 might just be to a test point, 1 and 2 are thicker. Anyways idk on that one.

Edited by astrosynthesist 2020-01-14 9:18 AM
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C:Amie Page Icon Posted 2020-01-14 9:34 AM
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Bloody good work sir!

You have probably done more for the Casio community in the last 3 days than the aggregate total of everyone else for the last 16 years
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astrosynthesist Page Icon Posted 2020-01-14 2:39 PM
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Factorite (Junior)

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Why thank you

I ain't done yet!
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astrosynthesist Page Icon Posted 2020-01-14 2:50 PM
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Don't quote me on this yet but I think I have found the part number for the power/rs232 header...

https://www.digikey.ca/product-detail/en/hirose-electric-co-ltd/3540...

UNTESTED

All digikey products in the series:
https://www.digikey.ca/products/en/connectors-interconnects/pluggabl...

Updated to link to more relevant parts

Edited by astrosynthesist 2020-01-14 2:53 PM
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astrosynthesist Page Icon Posted 2020-01-17 3:38 PM
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Quick update: There's a tiny microswitch inside the battery bay. That switch is actuated by the rechargeable battery pack. I cut a piece of eraser to the hole shape and when depressed the button allows me to operate the HPC from wall power with no main batteries inserted at all. The solid core wire seems to be too thick to use as contacts for my fake rechargeable pack... they get squeezed out of the way when I try to insert the pack. So I still don't have a fake rechargeable pack working... yet
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