This is a resource for those interested in understanding - and perhaps improving - the hardware used to implement our terrific Handheld PCs and related computers. Items to follow will include:

• What's in our machines and how they work.
• How to increase RAM directly by adding the necessary ICs.
• How to increase performance (overclocking, audio I/O, etc.).
• How to make other accessories (cables, power supplies, etc.).
• How to develop software inexpensively.

Suggestions and articles are most welcome! For now, emphasis will be on the Casio first generation HPCs (the Cassiopeia A10 and A11 and Compaq's PC Companion C120, C120+, C120++, and C140), as that's what I have and am studying (a C120).

*** DISCLAIMER *** All information here is for educational and recreational use only. Your computer is made of very tiny parts which are very sensitive to static electricity, corrosion from fingerprints, and are very easily broken or damaged by disassembly and reassembly. Do not attempt to disassemble or modify your computer in any way unless you have the equipment, training, and skills to do so. Such action *will* void your warranty. I make no claims that modifications made to other machines, no matter how successful, will necessarily work on yours. You are responsible for the health of your computer. While every attempt will be made to ensure the proper engineering of any changes, this is a hobbiest site and the information must be treated accordingly. For my personal credentials, you can check this.

(Legal_mode=OFF) A note - yes, it *is* possible to open and modify your HPC with a Radio Shack $20 soldering iron on the kitchen table. I *don't* recommend doing so as you run a considerable risk of modifying your fine computer into rubbish. But it has been done. You have been warned...

Challenge to Philips, Hitachi, NEC, LG, and HP HPC owners: Why should the Casio / Compaq owners have all the fun? Let's see some input or ideas from other HPC owners such as yourselves - send it and I'll put it here, or links to your information if you'd prefer. Our machines may differ, but there's lots they have in common. Let's dig in and have fun!

Computer Internals (Casio & Compaq): The best place to learn the details of the internals of Casio's machines mentioned above is with Casio's service manual which may be ordered from Pacific Coast Parts, among others. (Casio used to list all their parts dealers on the Web but the link has gone dead - phooey!) Included are schematics, pinouts, disassembly and test instructions, parts lists, and more. There are some minor errors and inconsistencies (DRAM is shown as two different NEC parts depending on the reference, not the Hitachi part used, among others) which don't reduce its usefulness.

Computer Internals (All SH-3): Hitachi's Web pages have all the technical details on the CPU and DRAM. It is also available on CD-ROM which you can get for free from Marshall Electronics (http://www.marshall.com). This includes many hundreds of pages of manuals, diagrams, application notes, etc. The Casio Service Manual is a tremendous resource as well.

Adding RAM (Casio & Compaq): The A10 and C120 machines have 2M of DRAM built in. The A11 and C140 have 4M of DRAM. The only difference is that the former machines didn't have one DRAM and its bypass capacitor soldered in. The DRAM is a Hitachi HM51W16160LTT-6 which is carried by Reptron Electronics, Inc. for about US$21 each (http://www.reptron.com). The bypass capacitor is a 0.1uF surface mount monolithic part; almost any one will work fine. The service manual shows how and where the IC goes as well as how to get to it.

Finding a source of actual DRAM parts is a challenge. There are four parts currently used to do the job: Hitachi's HM51W16160LTT-6 or HM51W16165LTT-6, or NEC's uPD42S16160LG5 or uPD42S16165LG5. Reptron was willing to send me two of their already allocated ICs but their cost is higher than they might be due to shipping and handling of only two parts. Marshall Electronics was happy to take my order for only US$7.59 each - but didn't have any to sell after all.

Once you get the parts and solder them in, it comes right up and runs just fine. Click here for step-by-step instructions.

Adding more RAM (Casio & Compaq): The 2M RAM add-on card (US$99) is a replacement board which is exactly the same as the one in a standard machine except that it has the DRAM IC and a bypass capacitor soldered in. The DRAM is the same as above as is the 0.1uF capacitor. Again, the service manual has details. Again, above precautions apply! Click here for full instructions on how to do it.

By the way, the RAM / ROM plugin card has provisions for a 1024 bit EEPROM - and signals to handle Flash memory. Does anyone know about using these?

Adding lots of RAM (Casio & Compaq): Still to be determined is whether the extra unused signals to the RAM/ROM board would allow memory expansion beyond 6M total RAM. The address decoding is done by a custom ASIC which precludes just piggybacking DRAM chips or other simple kluges. However, if the signals are sufficient a board could be made with existing ROM chips, an 8M DRAM or two, and a new ASIC to interface the DRAM. A 12M or 20M HPC with the PC card slot available for modem use would be nice...

Batteries (Casio & Compaq): The battery circuitry is surprisingly complex and well done. One result is that the handling of rechargeable (NiMH) batteries is done considerably differently than dry cells (the standard battery pack). While Radio Shack carries AA NiMH batteries for only US$9.99 a pair (RS part #23-525), the low-battery detect circuits won't know you're not using alkalines and will be somewhat harder on the cells. It also won't prevent excessive discharge (the NiMH pack uses separate contacts and the computer disconnects 'em if the voltage gets too low to protect the cells). The battery-to-+3.77 volt switching power supply even kicks in parallel inductors, diodes, and FETs to cut supply losses just for NiMH packs - which the Radio Shack approach can't make use of.

So are we condemned to either spend a pile on the factory battery pack or abuse other NiMH cells? Stay tuned - I want to see how easy it would be to convert a standard battery pack to a NiMH one by moving the contacts and adding a protrusion to press the NiMH detect switch.

Serial Cable pinout(Casio/Compaq): The serial cable uses a Hirose Electric connector that's not available yet in the USA. The connector used on the cable is designed for machine terminated wires, not soldering or user modification. None the less, several have asked for the pinout. For those who want another cable, I'd advise checking with Casio's or Compaq's Web sites.

The connector has 16 pins in two rows, with the rows staggered by a half-pin. The pins are numbered sequentially, alternating bottom and top, with pin 1 on the bottom row nearest the IR window, pin 2 on top nearest the IR window, and so on to pin 16 nearest the CTRL key.

Pin functions are:
01: NiCd Battery Negative terminal.
02: Not used (goes to battery compartment contact).
03, 08, 16: Digital ground (negative voltage point).
04, 05: NiCd Battery Pack charging terminal.
06, 07: Main external power positive voltage input (+5VDC input here).
09: Dock presence detect (ground if docked).
10: CTS
11: DCD
12: RXD
13: TXD
14: RTS
15: DTR

Null Modem (All): The serial cable supplied with our computers is wired as DCE (Data Communications Equipment) as compared to most serial ports which are DTE (Data Terminal Equipment). That's why you can plug the cable directly to your desktop PC and have the two communicate. But if you want to connect to an external modem or other serial device you're stuck.

A double-male D9M null-modem adapter is the answer. I don't know anyone who has them. But they're easy to make - you just connect two 9 pin male D connectors as follows:

Pins 1, 6 => 4
Pin 2 => 3
Pin 3 => 2
Pin 4 => 1, 6
Pin 5 => 5
Pin 7 => 8
Pin 8 => 7
Pin 9 - Pin 9: Don't connect either one to anything.

If you put the solder sides of two D9Ms facing each other with pins 1-5 on top, you'll find that connecting them is a straightforward process resulting in an adapter about 1 inch (2.5 cm) long.

Third Party Hardware Upgrades (All): Undoubtedly, as we learn more way to enhance our machines there will be those who offer to do so for others. If you are one who does so, I'll be happy to list your services on this site. Email me with the details. After all, not everyone is comfortable doing SMD soldering to add memory or what have you - so there's a market for anyone who wishes to make these upgrades to others' machines.

Cheap but complete development tool set (All): Developing Windows CE software currently requires using an interpreted language (BASIC, FORTH, LISP, etc.) or use of Microsoft's Visual C++ or Visual Basic. The latter two, to run them well, require the appropriate compiler (US$450 or so), the WinCE additions (US$180), and optionally Windows NT for debugging (US$280) - an investment of around US$900. For a professional grade development package that's quite reasonable. As a way to port or create programs for our US$99 - on - up computers, it's outrageous.

Hitachi currently gives away the GNU C++ development package for their SH-3 which is powerful and comprehensive but does not generate WinCE files. Cygnus Software gives away a complete GNU Win32 C++ development package but it's for the x86 family of CPUs. Microsoft gives away the WinCE add-ons to Visual C++ and Visual BASIC but they are made only for Microsoft's tools and are time limited (check Microsoft's CE Developers download pages for their CE 2.0 SDK).

Is anyone out there familiar with these three tools and have an informed idea on whether it would be practical to sort/merge them to come up with a GNU WinCE C++ for the SH-3? Or for the MIPS or other SH3 CPUs out there?

**News** You can find information on a GNU development system targeted at CE machines at http://duch.cz/gnuce/. Thanks to Marek Peca and his work there!!

Self hosted software (All): Check out OrbWorks Pocket C - it's a limited C flavored language but still potent enough to do quite a bit and inexpensive. You'll be glad you did! Also, NSBasic is a recent powerful BASIC with the modern trimmings worth checking out as well.

Automobile powered supply (Casio/Compaq): The power supply in these computers boosts the voltage from the batteries or external source to +5.0 Volts DC. That supplies any TTL circuitry used (including the PCMCIA card slot). As such, any supply which puts out more voltage than a normal battery pack but no more than +5 VDC will work fine. A +5 VDC 1.6 Amp supply is the one sold as an AC adapter.

Several users are looking into using a standard wide-range switching power supply to provide +5 Volts from a cigarette lighter jack in their car's dashboard, allowing unlimited use in the field. If used with the standard battery charger and NiMH rechargable batteries, you could even recharge in your car. I'll post some sources of such supplies after they are proven in the field, as well as parts list and wiring information.

Overclocking: The magazine Mobile PC from Japan has published a several page article in which the main CPU crystal of 10 MHz has another of 14.318 MHz and a switch added, allowing switching the processor from 40 to 57.273 MHz. Details are being sought for all of us to enjoy. Several have kludged this in on their own and have reported success albeit at the cost of somewhat increased battery consumption and potential clock errors.

Microphone: Many WinCE handhelds include a microphone and software to allow taking audio notes. It appears that not only is the microphone hardware missing, but the drivers to handle it are as well. So software that expects either crashes. I doubt that we'll see that changed but don't rule it out...

Other Requests: What would you like to see here? Let me know - and we'll see if we can figure it out together. Happy portable computing!

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