Kategorie: Linux

For those unaware, the REU plugged into the C64’s expansion port and added extra memory while also allowing for direct memory access (DMA) transfers – something the Sidekick64 couldn’t do. This meant data could be transferred to and from the main system memory whole bypassing the MOS Technology 6510/8500 CPU. “My RAD Expansion Unit was designed to do these transfers,” Carsten says. It’s a major triumph!

Radical thinking

There are many benefits to having the RAD Expansion Unit, which boosts the amount of available memory from the standard 64kB to as much as 16MB. “It helps to run Geos [a C64 OS] and it makes some tasks less annoying, such as copying disks in one go. It also functions as a RAM disk to accelerate working with the system,” Carsten says.

In order to create the project, then, two PCBs were produced: one to fit Raspberry Pi 3A+/3B+ and another to fit Raspberry Pi Zero 2 W (the latter creating a less expensive unit). “I didn’t want the glue logic that facilitates the bus communication with the available GPIOs to get too extensive and I wanted to avoid Complex Programmable Logic Devices and such which would prevent many people from building their own RAD,” Carsten says.

Indeed, the project was designed so that the RAD contains the glue logic to interface Raspberry Pi with the C64 bus. “You simply put it on to Raspberry Pi like a HAT and plug it into the expansion port of the Commodore 64,” Carsten continues. “The combination of a fast SoC and a decent number of GPIOs was great.”

An explosive result

There were challenges, of course. “The biggest was getting the bit banging right,” Carsten says. “Most of the communication has to happen within a time window of less than 500 nanoseconds – most often there’s significantly less time between all signals being read and putting data on the bus.”

To make the device run smoothly, Carsten had to use multiplexers. “More signals on the expansion port need to be read/written to than Raspberry Pi has GPIOs,” he explains. The correct data had to be put on the bus at the right time to prevent memory corruption and, in the worst case, random instructions being executed by the CPU, causing a crash. “In general, to get the timing right, I needed to hit intervals at a spacing of approximately tens of nanoseconds, which I did using CPU cycle counters.”

With all that in place, it was time to chill and RAD-Doom proved a great way to do so. Most of the processing is being done by Raspberry Pi (“it’s essentially a CPU replacement where the new CPU is a one-core ARM running at 1.4GHz with its own 512MB RAM,” Carsten says). But the important thing is that the tech demo uses the C64’s VIC-II graphics chip – and works! Sound is also streamed to the iconic SID chip.

“I wanted to see how the C64/C128’s VIC-II and SID performed if CPU power and memory was not an issue,” Carsten says. “I also wanted to experiment with real-time colour dithering for the VIC-II.” By making use of Doom to output graphics and sound, he’s certainly managed to achieve that.

As such, Richard decided to create his own system. “I was seeing articles and forum posts describing electronic finders (devices that use a camera and computer to determine absolute telescope pointing),” he says. “So I decided to see if I could build something I’d be happy using and sharing.”

Scoping the sky

Richard has based his project – called PiFinder – around a Raspberry Pi 4 computer and a Raspberry Pi High Quality Camera, with the idea being to create a device that would take images of the night sky to determine where a telescope is pointing by analysing the pattern of stars.

“I wanted PiFinder to be easily added to any type of telescope, requiring no setup aside from a clear view of the sky to indicate where the telescope is pointing,” Richard says. “I wanted to combine this ability to know where the telescope is pointed with an extensive catalogue of thousands of object locations to help an observer find objects in the sky with simple guidance on which way to push the telescope.” He achieved all of these things and more.

By having the camera constantly taking images, the PiFinder can get to work. “So long as the on-board Inertial Measurement Unit indicates the telescope is static, the camera is snapping images and feeding them to the solving algorithm,” Richard explains. “Depending on sky conditions and which camera is being used, it can take anywhere from 0.25 to 1.5 seconds to capture an exposure which contains enough stars to solve.”

Stars in his eyes

After an image has been taken, it’s processed using code released by the European Space Agency called Tetra3. “It implements a very fast system for extracting stars from an image and using distances between multiple sets of four stats in the image to produce a hash,” Richard says. “This hash can be quickly matched against a pre-computed database of star patterns to find candidate positions. Each potential position is then checked using other stars in the same image to verify the correct solution.”

Extracting stars from the image on a Raspberry Pi 4B computer takes just 100 milliseconds, while solving the image takes 44 ms. “This is all done on a separate thread so the next image can be acquired while the previous image is being solved,” Richard says.

“In practice, this means that the PiFinder can usually achieve one capture/solve per second. If using the Raspberry Pi Global Shutter Camera, it can achieve more than two captures/solves per second due to its much larger pixel size and low-light sensitivity.”

By cycling through several astronomical catalogues and even typing in the ID of a specific celestial body, users can use PiFinder to locate objects in the night sky, receiving simple guidance on which way to push the telescope in order to view them. Richard says it’s working well, which is why he released it to the public after seven months’ work. “I’ll continue to focus on making it as simple to replicate and build as possible as I get more feedback from others,” he reveals.

The first add-on module, USB/HDMI (£12/$12), connects directly to mini-HDMI and micro-USB ports, breaking them out into full-sized equivalents and separating the power, freeing up another USB port. Installation is as simple as lining up the connectors and pushing together, with no drivers required. Underneath, a header and power connector are exposed that are used to connect other modules, so you may require this module for compatibility.

But wait, there’s more!

Need some more USB ports? How about Ethernet? The USB/LAN module (£20/$20) does both. A ‘full-size’ module, it sits below our current setup, connecting via an exposed header on the USB/HDMI module. Easily snapping together, you now get an additional four USB connectors (two on the front, two on the back) and an Ethernet connector for hard-wired networking. Again, a one-minute install and Raspberry Pi OS recognises all peripherals without any additional software.

Now it’s show-time. The Display Module (£30/$30) is a 2.8-inch capacitive touchscreen that plugs into Zero’s GPIO. Framed in an attractive black bezel, with four programmable buttons, it transforms Zero into a stand-alone unit opening up the potential for makes. Drivers are required to get the screen running, which we found easy to install. A simple configuration system allows the buttons to be preprogrammed with common functions such as power off or reboot. Provided documentation explains how to take control of them yourself using GPIO. The screen is perfectly adequate, although you’ll need a stylus for meaningful use of the touch capabilities.

All in all, this is a great collection of add-on gadgets for your Zero. The modular nature means you can keep costs (and size) down. Argon has also teased future modules for further expansion. One slight niggle was a lack of access to GPIO and camera connectors, although this can be overcome with USB devices. It would also be interesting if documentation was provided on how you could make your own modules using the through-module header.

Verdict

9/10

Easier GPIO and camera access would be nice, but the exquisite design, tough materials, and sensible pricing more than make up for that. The Argon POD has seriously impressed.

Specs

Case: Dimensions: 35 × 80 × 20 mm; SD card access; Removable cover

USB/HDMI Module: Dimensions: 35 × 80 × 20 mm; 2 × USB; 1 × full-size HDMI; 1 x micro-USB power

LAN Module: Dimensions: 70 × 80 × 20 mm; 4 × USB; 1 × Ethernet

LAN Module: Dimensions: 70 × 80 × 16 mm; 2.8˝ capacitive touchscreen; 4 × buttons; IR sensor

It reminds me that each country, and often each region within a country, had its own computing startups, and their products reflected the unique cultural and technological idiosyncrasies of the time and place.

Around the world

The MCM/70, produced by the Canadian company Micro Computer Machines, holds a special place in the annals of computing history as one of the first, if not the first, personal computers. Introduced in 1973, it boasted an Intel 8008 processor, 4KB of RAM, and an APL (A Programming Language) operating system: another thing I’ve never heard of before.

The MCM/70’s unique design, including a twin cassette deck and a built-in segmented LED display, reminds me of a modern cyberdeck.

It’s a pleasure to see a reproduction of this iconic machine today.

In the US, the Apple II was a revelation when it was launched in 1977. It was the first computer many Americans ever saw (here in the UK, mine was a Dragon 32). The Apple II’s role in popularizing the concept of the personal computer cannot be overstated.

I preferred the Commodore 64, with its powerful multimedia capabilities. It became a beloved home computer, and also a favourite platform for game developers. It’s still my favourite.

Moving to the UK, the ZX Spectrum and the BBC Micro were pivotal in the country’s computing history. I had a ZX Spectrum, and despite its rubbery keyboard and modest specifications, it was a revolution in the home computing market due to its affordability. The BBC Micro, on the other hand, was a staple in schools, providing many British children with their first taste of computing. Over in Japan, the NEC PC-8801 and Sharp X1 series were leading the pack. I don’t think I ever saw one until visiting computing museums as an adult. Down under, the Microbee, an Australian-built computer, had a cult following. In the Soviet Union, locally produced machines like the Agat and the Electronika BK series were reverse-engineered Western designs.

Today, the world of computing can seem homogenous, dominated by a few large corporations. A MacBook is a MacBook all over the world. We use devices with eerily similar designs and identical operating systems. But in the 1980s, computers were wonderfully diverse. They were local, they were personal.

One of the most fascinating aspects of the Raspberry Pi is its ability to emulate retro computers. This enables enthusiasts to experience the computing past first hand, and younger generations to discover the rich history of personal computing.