Started to build my Raspberry Pi PiDrive System (for RetroPie)

I’ve started to rework my Raspberry Pi ‘dial-up’ interface. Instead of just handling my external VPN and SSH connections I’ve extended it to also function as an intermediate file server and Git repository (both via NFS+SSH). I’ve also inserted the Raspberry Pi into a new case and added a 1 TB 2,5″ drive. I think it can handle additional load so I plan to extend its capabilities to also serve as a RetroPie console.

By the way: the case and the connector cable between the drive and the Pi are both from WD Labs. The hard drive is not a PiDrive but a refurbished USB 3.0 1 TB disk (it was a recertified My Passport Ultra) before I’ve dismantled it. For me it was cheaper that way. If you’re looking for a similar setup and need an additional power supply and SD card maybe you should think about buying a Nextcloud Box (free shipping; handled by WD). You might not need to use its ‘cloud’ functionality but still get all hardware I’ve previously mentioned which I think is a pretty good bargain.

Sharp PC ROM File Collection (with Hashes)

This short post is to document Sharp PC ROMs I’ve come across so far. I’ve used MD5 and SHA1 checksums to allow their comparison. It would be nice if you could notify me of any ROMs out there that do not match the ones documented here… In an earlier post I’ve described a simple way to dump the ROMs.

  • Sharp CE-150
    Serial 31015xxx
    Memory Area A000-BFFF (8 kB)
    MD5 eb9aa5156c6849890b137799efc50a4b
    SHA1 a3aa02a641a46c27c0d4c0dc025b0dbe9b5b79c8
  • Sharp PC-1500
    Serial 20007xxx
    Memory Area C000-FFFF (16 kB)
    MD5 fbc55a9a8743e619b7709721ff5bcbff
    SHA1 d706d2e69cabbbbbe24f708cb3bc921fa1a2b704
  • Sharp PC-1500 / Sharp PC-1500A
    Serial 20011xxx (Sharp PC-1500)
    Serial 31070xxx – 57012xxx (Sharp PC-1500A)
    Memory Area C000-FFFF (16kB)
    MD5 8ebec8b0ef358645df14807c31df7d06
    SHA1 51a9e37a670b6cf199f0814e96a7e4fda6f44b60

Feel free to contact me and provide me with ROM file I do not (yet) have in my collection. I will also try to make the ROM files available in the next weeks.

Sharp PC-1500/1600 ROM Dump Method 2: Desoldering the ROM Chips

To make it clear from the beginning: this is a (possibly) destructive method of reading ROM chips. The process of extracting and possibly a resoldering of the memory chip might fail. In my case I’ve tested it on two Sharp CE-150 PCBs I’ve declared to be spare parts. It is only a proof of concept as there are simpler non-destructive ways of ROM extraction on a Sharp PC. I was just curious and so I’m describing my experiences.

Well… At first I did not want to desolder the ROMs: I started with the intention to use a set of probes attached to the individual pins of the chip to read the content of the Sharp PC / CE ROM chips. This did not work due to the narrow leg distance of the QFP chips (0.8 mm).

Probe Connection Problem

Desoldering QFP chips can be done rather quickly with a hot air gun. At least that’s the most comfortable way I know of. I usually add some flux and in some cases larger quantities of leaded solder. The latter decreases the melting point and speeds up the process. I don’t care about solder joints as the chips and the pads can easily be cleaned after the removal. Excessive amounts of solder can be removed with flux and a clean soldering iron tip.
Continue reading “Sharp PC-1500/1600 ROM Dump Method 2: Desoldering the ROM Chips”

Sharp PC Audio Output (CMT-OUT) Simulation in LTspice

This was a little test out of curiosity… I’m currently playing around with an amplifier circuit for the Sharp CE-150 audio output (CMT-OUT) and wanted to see if the signal I’m getting is already distorted when leaving my Sharp PC, or if my circuit and/or sound card is causing the distortions.

The CE-150 uses Frequency Shift Keying (FSK) to transfer binary data via audio signal (e.g. to a tape recorder). It sends four pulses of 1.27 kHz for a binary “0” and eight pulses of 2.54 kHz for a “1”.

Sharp CMT-OUT LTspice Schematic

To test the circuit I’ve taken the original design and simulated the circuit in LTspice (running under Linux with Wine). This tool allows the simulation of various analog (and digital) circuits – perfect for my test.

Sharp CMT-OUT LTspice Plot

Sharp CMT-OUT Audacity Plot

The result was – to be honest – pretty surprising for me. The upper screenshot shows the LTspice simulation of the output signal, the lower screenshot was taken from a WAV file in Audacity. I was not only able to simulate the circuit but also to use the resulting signals as a good approximation for my amplifier circuit (not shown). 🙂 One minor fix (also not shown) left was to adapt the transition time between a “0” and a “1” to better fit to the original curve.

Sharp PC-1500/1600 ROM Dump Method 1: Audio Transfer via CE-150 Extension

In this post I’m describing a method which is widely used to Dump RAM and ROM images on Sharp PC-1500 and PC-1600 systems. This method is non-destructive and can be used on most Sharp PC ROMs and extension cards. It only requires a Sharp CE-150 extension, an audio cable, and a computer with a microphone input (i.e. sound card).

Besides a plotter, the CE-150 Color Graphic Printer also provides two audio interfaces (line-in and microphone output). These were (and still are) used to transfer code or data between Sharp PCs and tape recorders. Today, such recorders are mostly outdated but the method works nonetheless with sound cards. Software tools are freely available (e.g. pocket-tools) that allow the transformation of recorded audio files into binary dumps and even further into BASIC code.

Continue reading “Sharp PC-1500/1600 ROM Dump Method 1: Audio Transfer via CE-150 Extension”

Sharp PC 1500/1600 Schematics Collection

To facilitate the access to Sharp Pocket Computer schematics I’ve started to collect and mirror some of them on my web site. This should allow Sharp PC 1500/1600 enthusiasts to update, modify, and especially to repair their hardware.

The Sharp PC 1500/1600 series are obsolete hardware. Their schematics are already freely available on the internet and therefore considered to be in the public domain. Please inform me if you own a copyright on some of this material and do not want it to be available on my web site.

Dumpster Dive: Sony Digital Mavica MVC-FD73 (Floppy Digital Camera)

Another day, another dumpster dive, another hit… a digital camera that uses 3.5″ floppy drives as storage device. A Sony Digital Mavica MVC-FD73.

My first surprise was that I was still able to charge the cameras battery. The second surprise was that it was still working flawless. And when doing some background research there was a third surprise that Sony still provides a manual (PDF). I did not expect any of these points.

Specifications
MVC-FD73
Max. resolution 640 x 480 (0.4 megapixels)
Sensor type CCD (ISO 100)
Optical zoom 10x (focal length ~ 40-400 mm)
Screen size 2.5"
Screen dots 84,000
Min shutter speed 1/60 sec
Max shutter speed 1/4000 sec
Weight (inc. batteries) ca. 500 g
Dimensions (ca.) 138 x 103 x 62 mm
Continue reading “Dumpster Dive: Sony Digital Mavica MVC-FD73 (Floppy Digital Camera)”

Review: Addifix 9 Mechanical Number Cruncher and Pocket Calculator

While trying to explain the meaning of the carry digit during addition an subtraction to my oldest son, I’ve given him a nice little device to play with: the Addifix-9 number cruncher.

I’ve briefly mentioned this device before in a post. This time I’ve made a short video about the mechanical calculator in action and present more details:

In the 1950s/60s The Addifix series was sold as “Addifix-9 Taschenrechenmaschine” by the German mail-order company Neckermann. Its predecessor was the Addiator from Carl Kübler which was sold since the early 1920s  [Source: sliderulemuseum.com]. The underlying mechanical principle is quite old (an documented example is the mechanical calculator by Claude Perrault from the 17th century).

The Addifix is a pocket-sized (13 x 9 cm) slide adder that can be used from both sides – one side for addition and one for subtraction. The slides (one for each digit) are handled with a metal stylus.

HIF6A-60PA-1.27DS as Replacement for JAE PICL-60P-LT Sharp-PC Connector

Needing a replacement for the long ago discontinued Sharp-PC connector JAE PICL-60P-LT, I dug through a lot of datasheets and finally found a pin-compatible one:

Hirose HIF6A-60PA-1.27DS – Datasheet
Hirose HIF6A-60PA-1.27DS – Digi-Key Link

The connector fits good enough for my purposes. If necessary removing a bit of the plastic case left and right of the pins improves the connectivity as the replacement connector is a bit broader.

There is also a version with mounting holes (HIF6B-60PA-1.27DSL) which I will also try to get my hands on (currently not in stock).

My original solution was to use a 2×30 1.27×2.54 pin header as shown in this post, but the narrow space between the pins led to serious constraints in designing a new interface board (more about that when it’s ready).
HIF6A-60PA-1.27DS JAE PICL-60P-LT 1