Had the pandemic not upended many of this summer’s fun and games, many of my friends would have made a trip to the MCH hacker camp in the Netherlands earlier this month. I had an idea for a game for the event, a friend and I were going to secrete a set of those low-power FM transmitters as numbers stations around the camp for players to find and solve the numerical puzzles they would transmit. I even bought a few cheap FM transmitter modules from China for evaluation, and had some fun sending a chiptune Rick Astley across a housing estate in Northamptonshire.
To me as someone who grew up with FM radio and whose teen years played out to the sounds of BBC Radio 1 FM it made absolute sense to do a puzzle in this way, but it was my personal reminder of advancing years to find that some of my friends differed on the matter. Sure, they thought it was a great idea, but they gently reminded me that the kids don’t listen to any sort of conventional broadcast radio these days, instead they stream their music, so very few of them would have the means for listening to my numbers stations. Even for me it’s something I only use for BBC Radio 4 in the car, and to traverse the remainder of the FM dial is to hear a selection of easy listening, oldies, and classical music. It’s becoming an older person’s medium, and it’s inevitable that like AM before it, it will eventually wane.
There are two angles to this that might detain the casual hacker; first what it will mean from a broadcasting and radio spectrum perspective, and then how it is already influencing some of our projects.
Continue reading “FM Radio, The Choice Of An Old Generation”
The parenthood of any invention of consequence is almost never cut and dried. The natural tendency to want a simple story that’s easy to tell — Edison invented the light bulb, Bell invented the telephone — often belies the more complex tale: that most inventions have uncertain origins, and their back stories are often far more interesting as a result.
Inventing is a rough business. It is said that a patent is just a license to get sued, and it’s true that the determination of priority of invention often falls to the courts. Such battles often pit the little guy against a corporate behemoth, the latter with buckets of money to spend in making the former’s life miserable for months or years. The odds are rarely in the favor of the little guy, but in few cases was the deck so stacked against someone as it was for a young man barely out of high school, Philo Farnsworth, when he went up against one of the largest companies in the United States to settle a simple but critical question: who invented television?
What does a Hackaday writer do when a couple of days after Christmas she’s having a beer or two with a long-term friend from her university days who’s made a career in the technical side of digital broadcasting? Pick his brains about the transmission scheme and write it all down of course, for behind the consumer’s shiny digital radio lies a wealth of interesting technology to try to squeeze the most from the available resources.
In the UK, our digital broadcast radio uses a system called DAB, for Digital Audio Broadcasting. There are a variety of standards used around the world for digital radio, and it’s fair to say that DAB as one of the older ones is not necessarily the best in today’s marketplace. This aside there is still a lot to be learned from its transmission scheme, and from how some of its shortcomings were addressed in later standards. Continue reading “Anatomy Of A Digital Broadcast Radio System”
Here’s a question: when did you last listen to an AM radio station? If your answer is “recently”, chances are you are in the minority.
You might ask: why should you listen to AM? And you’d have a point, after all FM, digital, online, and satellite stations offer much higher quality audio, stereo, and meta information, and can now be received almost anywhere. Even digital receivers are pretty cheap now, and it’s by no means uncommon for them to not even feature the AM broadcast band at all. Certainly this has driven an exodus of listeners to the extent that AM radio has been in slow decline for decades, indeed it’s disappearing completely in some European countries.
Continue reading “AM, The Original Speech Transmission Mode”
The ESP8266 is well known as an incredibly small and cheap WiFi module. But the silicon behind that functionality is very powerful, far beyond its intended purpose. I’ve been hacking different uses for the board and my most recent adventure involves generating color video from the chip. This generated video may be wired to your TV, or you can broadcast it over the air!
I’ve been tinkering with NTSC, the North American video standard that has fairly recently been superseded by digital standards like ATSC. Originally I explored pumping out NTSC with AVRs, which lead to an entire let’s learn, let’s code series. But for a while, this was on the back-burner, until I decided to see how fast I could run the ESP8266’s I2S bus (a glorified shift register) and the answer was 80 MHz. This is much faster than I expected. Faster than the 1.41 MHz used for audio (its intended purpose), 2.35 MHz used for controlling WS2812B LEDs or 4 MHz used to hopefully operate a reprap. It occasionally glitches at 80 MHz, however, it still works surprisingly well!
The coolest part of using the chip’s I2S bus is the versatile DMA engine connected to it. Data blocks can be chained together to seamlessly shift the data out, and interrupts can be generated upon a block’s completion to fill it in with new data. This allows the creation of a software defined bitstream in an interrupt.
Why NTSC? If I lived in Europe, it would have been PAL. The question you’re probably thinking is: “Why a dead standard?” And there’s really three reasons.
Continue reading “Color TV Broadcasts Are ESP8266’s Newest Trick”
[CNLohr] has made a habit of using ATtiny microcontrollers for everything, and one of his most popular projects is using an ATTiny85 to generate NTSC video. With a $2 microcontroller and eight pins, [CNLohr] can put text and simple graphics on any TV. He’s back at it again, only this time the microcontroller isn’t plugged into the TV.
The ATtiny in this project is overclocked to 30MHz or so using the on-chip PLL. That, plus a few wires of sufficient length means this chip can generate and broadcast NTSC video.
[CNLohr] mentions that it should be possible to use this board to transmit closed captioning directly to a TV. If you’re looking for the simplest way to display text on a monitor with an AVR, there ‘ya go: a microcontroller and two wires. He’s unable to actually test this, as he lost the remote for his tiny TV from the turn of the millennium. Because there’s no way for [CNLohr] to enable closed captioning on his TV, he can’t build the obvious application for this circuit – a closed caption Twitter bot. That doesn’t mean you can’t.
Continue reading “ATtiny85 Does Over The Air NTSC”