Software Hacks

903 Articles

Circuit Impedance Calculations Without Cumbersome Simulations

March 2, 2021 by 11 Comments

Using circuit simulating software like SPICE can be a powerful tool for modeling the behavior of a circuit in the real world. On the other hand, it’s not always necessary to have all of the features of SPICE available all the time, and these programs tend to be quite expensive as well. To that end, [Wes Hileman] noticed an opportunity for a specific, quick method for performing impedance calculations using python without bulky, expensive software and came up with a program which he calls fastZ.

The software works on any network of passive components (resistors, capacitors, and inductors) and the user can specify parallel and series connections using special operators. Not only can the program calculate the combined impedance but it can perform frequency analysis at a specified frequency or graph the frequency response over a wide range of frequencies. It’s also running in python which makes it as simple as importing any other python package, and is also easy to implement in any other python program compared to building a simulation and hoping for the best.

If you find yourself regularly drawing Bode plots or trying to cobble together a circuit simulation to work with your python code, this sort of solution is a great way to save a lot of headache. It is possible to get the a piece of software like SPICE to to work together with other python programs though, often with some pretty interesting results.

Fixing The Only Thing That’s Slow About Grand Theft Auto V

March 2, 2021 by 13 Comments

The driving, crime, and general mayhem game Grand Theft Auto V is something of a phenomenon that has lasted for the last seven or more years. Whether following the in-game missions, driving around like a hooligan for fun or performing crazy stunts, the depth of detail in its landscapes and the continual improvements to gameplay that have arrived over the years have assured it a massive following across multiple platforms. The game is not without its problems though, one of which is an unreasonably long loading time for its online version. This annoyed [T0st] to the extent that it was worth the effort of looking under the hood to find out where the problem lay.

It was evident that for PC users the effect varied depending on the hardware present. Furthermore AMD processors seemed worse-hit than Intel ones, and indeed they found an entire core maxed out by a couple of processes during the wait. Some diagnostics and disassembly led the trail to some string processing code which was identified as a JSON parser. This was not simply parsing the JSON but also performing a check for token uniqueness in an extremely inefficient manner, causing the whole process to be extremely slow. Sone nifty patching in a DLL containing a much more efficient function with a cache for unique values saved the day, and delivered an impressive 70% speed-up. It’s to be hoped that the game’s developers will take note, and a future GTA V update will deliver a fix.

Driving a car from a third-person viewpoint in a game like GTA V is a hoot. In real life though, not so much.

Thanks [Thanatos Erberus] for the tip.

Oddball X86 Instructions

February 25, 2021 by 66 Comments

David Letterman made the top ten list famous. [Creel] has a top ten that should appeal to many Hackaday readers: the top 10 craziest x86 assembly language instructions. You have to admit that the percentage of assembly language programmers is decreasing every year, so this isn’t going to have mass appeal, but if you are interested in assembly or CPU architecture, this is a fun way to kill 15 minutes.

Some would say that all x86 instructions are crazy, especially if you are accustomed to reduced instruction set computers. The x86, like other non-RISC processors, has everything but the kitchen sink. Some of these instructions might help you get that last 10 nanoseconds shaved off a time-critical loop.

Continue reading “Oddball X86 Instructions” →

Software Challenge’s Solution Shows Reverse Engineering In Action

February 16, 2021 by 3 Comments

[0xricksanchez] participated in a software reverse-engineering challenge and recently wrote up the solution, and in so doing also documented the process used to discover it. The challenge was called Devil’s Swapper, and consisted of a small binary blob that output a short message when executed. The goal of the challenge? Discover the secret key and the secret message within. [0xricksanchez]’s writeup, originally intended just as a personal record, ended up doing an excellent job of showing how a lot of reverse engineering tools and processes get applied to software in a practical way.

What’s also great about [0xricksanchez]’s writeup is that it uses standard tools and plenty of screenshots to show what is being done, while also explaining why those actions are being chosen and what is being learned. It’s easy to follow the thought process as things progress from gathering information, to chasing leads, and finally leveraging what’s been learned. It’s a fascinating look into the process of applying the reverse engineering mindset to software, and a good demonstration of the tools. Give it a read, and see how far you can follow along before learning something new. Want more? Make sure you have checked out the Hackaday 2020 Remoticon videos on reverse engineering firmware, and doing the same for PCBs.

Ghidra Used To Patch Fahrenheit Into An Air Quality Meter

February 15, 2021 by 73 Comments

Even though most of the world population couldn’t tell you what room or body temperature is in Fahrenheit, there are some places on this globe where this unit is still in common use. For people in those areas, it’s therefore a real hassle when, say, a cheap Chinese air quality measurement systems only reports in degrees Celsius. Fortunately, [BSilverEagle] managed to patch such a unit to make it display temperature in Fahrenheit.

The reverse engineering begins by finding a way to dump the firmware. It’s nice to hear that [BSilverEagle] used some the skills demonstrated in [Eric Shlaepfer’s] PCB reverse engineering workshop from Hackaday Remoticon last November to trace out the debug header and the SWD pins of STM32F103C8 MCU. After that, OpenOCD could be used to dump the firmware image, with no read protection encountered. The firmware was then reverse-engineered using Ghidra, so that [BSilverEagle] could figure out where the temperature was being calculated and where the glyph for the Celsius symbol was stored. From there this it was a straight-forward rewrite of those two parts of the original firmware to calculate the temperature value in Fahrenheit, change the glyph and reflash the MCU.

So why buy this thing in the first place if it didn’t spit out units useful for your current locale? Cost. Buying this consumer(ish) device was about the same cost as buying the individual parts, designing and manufacturing the PCB, and writing the firmware for it. The only downside for their use case was the lack of Fahrenheit. Not a problem for those who demand full control of the hardware they own.

Need a boot camp for using Ghidra? Matthew Alt put together a spectacular video series on Reverse Engineering with Ghidra.

Legacy Digital Photos, With A Side Of Murphy’s Law

February 14, 2021 by 26 Comments

[Dave Madison] came across some old digital photos, and in his quest to access them, he ran into quite a few challenges. The saga brings to mind both Murphy’s Law, and while [Dave] prevailed in the end, it required quite a few more steps than one might expect.

The one smooth part of the process was that Konica’s proprietary software had a handy JPEG export feature.

Here’s the scene: in the late 90s, Konica partnered with photo shops to provide a photo scanning service, delivering digital scans of film photos on 3.5″ floppy disks, and that’s exactly what [Dave] had to work with. The disks were in good condition, and since modern desktop computers still support floppy drives and the FAT filesystem, in theory all one needs to do is stick disks into the reader one at a time in order to access the photos.

Sadly, problems started early. A floppy drive is revoltingly slow compared to any modern storage device, so [Dave]’s first step was to copy all of the files to his machine’s local storage before working on them. This took a bit of wrangling to deal with 8.3 format file names and avoid naming collisions across disks while still preserving some metadata such as original creation date. It was nothing a quick python script couldn’t handle, but that soon led to the next hurdle.

The photos in question were in an obsolete and proprietary Konica .KQP format. [Dave] went through a number of photo viewing programs that claimed to support .KQP, but none of them actually recognized the images.

Fortunately, each disk contained a copy of Konica’s proprietary “PC PictureShow” viewer, but despite having a variety of versions dated between 1997 and 2001 (making them from the Windows 98 and Windows ME eras) [Dave] could not get any version of the program to run in Windows 10, even with compatibility mode for legacy programs enabled. The solution was to set up a Windows XP virtual machine using Oracle’s Virtualbox, and use that to ultimately run PC PictureShow and finally access the photos. After all that work, [Dave] finally had a stroke of luck: Konica’s software had a handy feature to export images in JPEG format, and it worked like a charm.

In the end, [Dave] was able to save 479 out of the 483 images on the old floppy disks, with a reminder that proprietary formats are a pain. The disks and images may have been over twenty years old, but the roots of digital imaging go considerably further back than that. Take a few minutes out your day to read a bit about Russell Kirsch and the first digitized image, that of his three-month old son in 1957.

Can You Code Without Google?

February 13, 2021 by 106 Comments

Imagine for a moment that something has taken out your phone line, cell, and fibre connection so you have no internet. For some of you this may even be reality, but go with it and imagine yourself deciding to use your unexpectedly disconnected lockdown time pursuing that code project you always promised yourself. You pull out your laptop and fire up a code editor. Can you write code that works, without the Internet as a handy crib sheet? [Austin Z. Henley] couldn’t, when he tried writing a straightforward web app. He uses it as a hook to muse on the nature of learning, and it’s certainly a thought-provoking subject.

It has become an indispensable tool for the engineer and the coder alike, to constantly refer to online knowledge. This makes absolute sense, as it provides a reference library that will be many orders of magnitude in excess of anything an individual can possibly hold personally.

This holds true whether the resource takes the form of code snippets from StackOverflow or GitHub, or data sheets from TI or Microchip. Even our calculations have moved online, as it’s often much quicker to use an online calculator on a web page to derive for example an impedance calculation. This is not necessarily a bad thing, instead it’s an enabler; skills that used to take months to master due to slow information access can now be acquired in an afternoon. But it does pose the interesting question, in the Internet age what is the measure of an expert coder? Is it the ability to produce the code effectively with whatever help is available, or is it a guru-like mastery of the code? Maybe it’s both. If you have the Internet, give us your views in the comments.