Children of the 1980s who had an interest in technology were lucky indeed. As well as the first generations of home computers at their disposal they had the expectation to program them, something which the generation that followed had lost.
Traditional children’s publishers enthusiastically embraced the home computer boom, and probably for the only time in history there were books aimed at children covering subjects like machine code, or interfacing to microprocessors.
If you are British, the most memorable of these books came from Usborne Publishing. Their format of colourful cartoons and easy to digest layout have made them something of a cult object among the now-grown-up generation who first received them, and Usborne themselves have cleverly exploited their heritage to promote their current offerings by releasing some of them as PDFs. And now, to promote their latest title, “Coding For Beginners Using Python”, they’ve released five more (scroll down to see). Titles are “Practice Your BASIC”, “Better BASIC”, “Computer Controlled Robots”, “Experiments With Your Computer”, and “Keyboards & Computer Music”, which join the fifteen they’ve already released.
Obviously they are heavily based around the microcomputers of the 1980s, but of course for most Hackaday readers that will be their chief attraction. Either way they’re an interesting read, and should you happen to have a few old micros lying around then maybe you could have a go at some of the projects.
Black and white NTSC is simple – it can, and was, done with vacuum tubes for a long, long time. Color is just weird, though. It runs at 29.976 frames per second, uses different phases of the carrier for different colors, and generally takes a while to wrap your head around. [Sagar] is doing a series on the intricacies of NTSC, and the latest post deals with color and progressive scanning versus interlacing, or as it is better known, how classic game consoles and home computers generate video.
The test bed for [Sagar]’s video experimentations is a circuit containing an ATMega16, a 4-bit shift register, and a 14.31818 MHz clock. This clock is much faster than the 3.579545 MHz clock in an NTSC carrier frequency – exactly four times as fast – allowing the shift register to output four different phases of the carrier frequency a 0°, 90°. 180°, and 270°. Playing with some of the pins on the ATMega in the circuit results in a palette being generated on any old TV.
NTSC requires interlaced scanning, or sending an entire screen of even lines, then an entire screen of odd lines, at around 60 fields per second. The Nintendos and Segas of yesteryear didn’t bother with this, instead opting to send half the vertical resolution at double the frame rate. This is known as a progressive scan. [Sagar] found that this resulted in some image artifacts when displayed on a modern LCD, and moving back to an interlaced mode fixed the problem. All the code and files are up on the gits. If you’re feeling adventurous, this is exactly how projects like the Uzebox have created homebrew game consoles using little more than the ATMega found in [Sagar]’s build.