The SiliconLabs SI7021 is a very popular sensor for measuring temperature and humidity. It uses the I2C bus and is easily accessed from the ESP9266 or ESP32. Some breakout boards use different variants of the chip, namely the measurement Specialties HTU21D or even the Sensirion SHT21. These chips are more or less compatible to one another, but some don’t implement all the commands. However temperature and humidity can be used on all those chips. Today I’ll walk you through a tutorial of accessing the SI7021 via the Arduino Wire library.
The VGA cards for historic PCs have an analog video output that is being driven by a so called RAMDAC. This is an IC that converts the digital framebuffer information into analog VGA signals. Modern PCs don’t need this anymore since they use digital output (like HDMI and DisplayPort) and digital displays. But our old retro machines use this to drive either an LCD or a traditional CRT. There are good RAMDACs out there and bad ones. One problem some RAMDACs have is noise when the VGA palette registers are written. This happens in games and demos for example when the screen is fading in or out. I found a supplier of new old stock INMOS RAMDACs, and I hope that replacing the cheap ADV RAMDAC on my Tseng ET4000 will remove the noise that I am seeing.
It’s summer and it’s hot. And what better to code than another classic demo scene effect: the ubiquitous fire. But we will do it with a twist. The naive implementation is slow, very slow. Especially on older 286-486 computers. We will optimize the actual algorithm a bit and utilize a hidden VGA function that gives us scaling in the X-direction by a factor of 4 for free.
The holy grail of PC soundcards include a few special devices. But one of them is surely the Gravis Ultrasound. It allowed mixing of 32 independent channels with (near) CD quality. This could be used for sound effects or music, and was particularly popular in the demo scene. But also game classics such as Jazz Jackrabbit, One Must Fall, Epic Pinball and Pinball Fantasies used the card to great effect. However today an original Ultrasound costs anywhere between 200-400 EUR, which is a bit too expensive in my opinion. So we try out a cheap homebrew clone! Meet the GUSar lite!
In 2019 Sam Demeulemeester (he’s actually Belgian, although I say French in the video) did a Kickstarter for the ATX2AT smart adapter. It allows you to safely attach a modern ATX PSU to a retro mainboard with AT connectors. That is your precious 286, 386 or higher will now be safe from overcurrents due to wrongly inserted CPUs, broken expansion cards, failing tantalum capacitors or rogue power supplies. It might not save the world, but it will probably save your valuable retro PC. I already lost two precious mainboards and am glad to have finally received the ATX2AT smart adapter!
There are two kinds of soldering PCBs: through hole and SMD. Through hole uses components with leads, which are threaded through holes (hence the name) in the PCB and then fixed to the PCB with solder. SMD uses Surface Mounted components. That is, very miniaturized components that are soldered onto the surface of the PCB, without using leads.
Due to the small size of the components it is at first much harder to solder than for classic through hole parts. To save you from the misfortunes of failed projects, there are practice kits available. We will assemble one such example today and I will try to teach you the basics of SMD soldering as well as some more advanced tricks.
The Innovation SSI-2001 was a very early PC sound card which appeared roughly during the release period of the Adlib. It was supported only by a handful of games and disappeared very quickly from the market. What makes it notable is the fact that it used the MOS6581 also known as the SID as its core. This chip was better known as the chip that drove the Commodore 64’s sound. Hence this card is particularly interesting. Early this year I hand soldered a replica of this card, known as the Renovation SSI-2001. Today we want to test drive a couple of games and compare different SID implementations: An original MOS6581, a SwinSID nano and the ArmSID. Can the much cheaper emulated SIDs hold a candle to the expensive and ever rarer original in this setting? We also take a short stab at getting the SID to produce a tone using MS DOS QBasic!
I am a big fan of interactive fiction, better known as text adventures. I am also a big fan of MS DOS games. And retro games in general. And when there is a new release of a retro game, a text adventure, which supports MS DOS and other platforms, I am all ears. Enter: The Curse of Rabenstein. A brand new release with a nice physical big box with lots of goodies. But is the game also a goodie? Let’s see…
I got a question in the YouTube comments about the sine tables that we used for a few animations, like the Copper Bars, the Smooth Scrolling etc. In this episode I try to explain why and how to create sine tables. The idea is to speed up computations, since computing the sine or cosine — even with an FPU — takes an awfully long time on early MS DOS machines.
After the 1084S monitor, my Amiga 500 gets an external Gotek USB Floppy Drive emulator. To be able to boot from it, we install a DF0 switcher. Many demos and games on the Amiga can only be booted from the first floppy drive, DF0. The external drive is called DF1. With the switcher we can toggle the external drive to be either DF0 or DF1.