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Logitech N395 numeric keypad for Linux

2019-12-31 22:15:31,  In: Hack, Linux

#Logitech N395 numeric keypad for Linux
# For =, ( and ) keys, version which does "Alt" combos.
#USAGE: Write this to a text file, run at start: 
#          xbindkeys -f /path/to/file
#
# WARNING: THIS WILL UNFORTUNATELY NOT WORK IN MANY TERMINALS.
#    due to Alt being used...
#
# Some definitions from: 
# http://users.skynet.be/linux-rixensart/3_peripheriques.html#keypad
#Keypad ( "sleep 0.04 && xdotool type "("" m:0x18 + c:90
#Keypad ) "sleep 0.04 && xdotool type ")"" m:0x18 + c:87
#Keypad = "sleep 0.1 && xdotool key BackSpace && sleep 0.04 && xdotool type "="" m:0x18 + c:85
#Some other things in N305: # - The "Excel" key runs Win+R then blindly types "excel" and presses # Return. This seems not to be changeable in hardware. Symlink # LibreOffice/OpenOffice/Gnumeric to "excel" and it may run in X. # - The calculator launches XF86Calculator key. # - The "Window" key fires single Alt-Tab. # # Good Luck as this is really poorly configurable. MCbx

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Mikrosha repair log

2019-11-22 12:35:44,  In: Electronics, Retrocomputing

Mikrosha is a Soviet home/educational microcomputer made in LEMZ plant near Moscow. This looks like a quite consistent 8080 system with a CPU, a few 8255s, 8275 as display controller, DMA controller, timer and 32kB of RAM in 2118 clones (in case of failure I will be able to substitute with modified 4164, knowing that it's possible to put modified 4164 as 4116 and 2118s are like 4116s but single-voltage).
Review of the power supply unit shown that the -5V regulating transistor (total current: 50mA, no protection at all, dissipation: really poor) conducts C-E in both sides. That's why as I measured it initially, it gave -11.3V in -5V line. Replaced the transistor with the first 100mA PNP I had in my "desolder box", voltages returned to normal. The power supply unit has separation coil, transformer and linear regulators for...

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A TV Tennis game description

2019-08-24 21:17:37,  In: Electronics, DIY

The device, a TV Tennis game, has been made using designs from different sources, especially a description in "Radioamator" and images of the prototype. The general rule is similar to "Odyssey" but the signal mixing is simplified while still giving TV-friendly signals. There are only NPN signal transistors and 74 chips, to be exact one 7474 dual flipflop, 7473 as divider and 7493 as additional divider. Other chips are 7400, in many possible configurations. All other things like delays or integrations are made using discrete components. If someone wants to build a similar unit, prepare for a long tuning and selection of components.
This is a general view of the device. It has a power switch, 1/2 player switch and speed setting. Two controllers consist of X/Y pots, serve and "Lift" buttons which changes deflection...

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Things to note: SyncThing under WinXP

2019-03-28 00:17:18,  In: Other

PROBLEM: SyncThing 1.0.1 used to synchronize data on different machines updates itself to newer version, also under WinXP. Newer versions don't work under WinXP, so the program does not start again. Literally it's damaging itself.
SOLUTION: Turning automatic update off does NOT work in 1.0.1 it's specified like "Disabled by administrator" in options related to it. To disable updating manually, open your C:\Documents and Settings\[USERNAME]\Application data\Syncthing\config.xml ("Application Data" may be translated) and change autoUpgradeIntervalH parameter to zero (0). Now downgrade to 1.0.1 and start it. Currently it works, if it will stop there will be a problem with lots of XP machines connected to programmers and similar machinery.
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EU Copyright directive: Internet users like it.

2019-03-23 11:15:22,  In: rants

Recently lots of media attention is focused on new European "Copyright directive", especially on laws allowing to implement upload filters and a so-called "link tax". So I decided to do something instead of this website darkening fashion and describe why it's too late for any protests. Let's go to the point: Both of these regulations: Upload filters and so-called "link tax", describe things which are already present since at least a decade, they have been already implemented and embraced by community - and quite everyone seems to be happy with it. Automatic upload filters are present in all platforms, as well as most hostings, services and rented private servers. There are a few forms of these filters:
- Legally censoring content using "terms of service" contract, which in practice is one-side, means you have to obey it and they may or may not. This is visible well in politically sensitive content, when the censorship noted in ToS does not exist when it's neded to divide people, and is exaggerated when...

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Things to note: PC LED display jumpers

2019-02-15 17:45:17,  In: Retrocomputing

In PC casings a typical problem happens with LED display configuration. Configured to "HI/LO", it may be needed to change it, and jumpers are not always well laballed. There are many configurations. A simple one has two rows for two digits and one small row for hundreds. In this configuration, jumper settings are quite simple: You specify "turbo" configuration by placing jumpers across the row, and "normal" along the row. This way it is possible to set any value. Another type, with two digits, contains two rows of three and a logic chip. I found six revisions of these, all with different settings. What is important in this display it is needed to have Turbo connected some way to make it display at all. In some versions bottom row is for Turbo, while top for non-turbo, in other the middle row can be configured by horisontally aligning their jumpers, while Turbo required to put jumpers above and below. Some PCBs allow to be mounted inverted, so even if there's more than 199MHz, you can reverse it and have...

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Restoring the old PC-XT clone mainboard

2018-10-27 01:42:04,  In: Electronics, Retrocomputing

A long time ago I got an XT mainboard. The history of it is known: previous owner got it from someone else, who told that it is damaged and cannot be easily repaired, so it became an interesting exhibit in a bookshelf. It was for last 2 years in my stuff and finally I decided to restore it to the working condition.

The mainboard is a really old one - it has an additional ISA edge connector on the side, all TTL chips from around 1984-85, socketed, but it was not an IBM. The logo, visible on a silkscreen under the processor, resembles a stylish written "S" letter with its center line shaped in an american resistor symbol.
It was a clone, but a clone made with some uncertainity. Not that there are circuit errors, it electrically still is a 5160, but the design itself is... like someone took schematics from the technical manual, looked at original PCB and said "OK, let's try to design it again", and this was the first try, made quickly to verify is everything OK. The mainboard has a piece of breadboard...

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Curiosities: Inside a 1970s professional multimeter

2018-08-12 17:32:44,  In: Electronics, Curiosities

Mera V640 is a multimeter made by Polish Meratronik plant in 1970s. It is an analog meter, able to measure voltages (1.5mV - 1500V), currents (0.15uA - 1.5A) and resistance. With specialized probes it was possible to measure high frequencies and even temperature. In 1970s Poland started to make international deals, usually with licenses. Some licenses were bought, like from British ICL for their computer designs, German (western) Grundig (tape players), or Japanese Busicom for calculators, but Poland also manufactured their equipment for export. In 1972 the Masteranger 639 multimeter has been made for Conway, a Canadian electronics company, and manufactured purely for export. The design was successful enough that it was also manufactured for British Marconi company as TF 2650. Year later it was also sold in Poland, under V640 name, after some changes in range switch and adding temperature probe.
These times, export and import with eastern block country was very different than typical transaction,...

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Expanding Arduino UNO memory with 32kB static RAM chip

2018-07-04 17:42:04,  In: DIY, Electronics

Arduino Uno is a cheap microcontroller platform which can be used in lots of applications. If we prototype our solution using Arduino board, it is possible to dump the Arduino board and use single microcontroller instead which is even cheaper and looks more professional even on an universal solder-in PCB. However, ATMega328 chip used in Uno has a significant drawback - its memory which is only 2kB. If we want to make a small control device it's not a problem, but for some specific applications 2kB may be too small.
For example, since few weeks I have an idea to develop a BASIC computer using AVR chips. Implementation of Tiny BASIC uses some memory and has some code clutter which can be replaced with something more usable by the cost of e.g. moving storage code to external devices. Unfortunately Tiny BASIC leaves a very small memory for user's program and its variables.

So what are options to add RAM into Arduino?
- Use a larger Arduino module. This solution is present in Internet forums all...

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Debian Linux on a GPD Win

2018-01-05 22:09:17,  In: Linux, Debian

OK, so I bought a GPD Win. Small, Intel-powered computer with 4GB of RAM, Atom processor (2-core, 4-thread?) and 64GB of SSD. Unfortunately, with Windows 10 by default.
Because I found Windows 10 unbearable even when following the manuals to optimize and make it smaller, I decided to try with Debian.
Unfortunately this device is a completely closed UEFI machine so it doesn't allow much modification. However, I found Debian USB sticks, when not touched, bootable.
This is a set of notes which are based on Hans De Goede's blog entry about installing Fedora on GPD Win.

   What will be needed

Installation of Linux on GPD Win is quite specific and different than typical Debian installation. Many drivers for things like Wi-fi or sound chip are absent, improperly installed or misconfigured so it's needed to patch the system up. To do it, you need
- A GPD Win
- A 4GB USB stick or bigger
- USB hub. The faster the better.
- USB wi-fi adapter...

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