LEAP#351 SDR with cheap R820T2/RTL2832U dongles
Cheap SDR dongles? Apparently it all started when a bunch of folks (Antti Palosaari, Eric Fry and Osmocom) found that the signal I/Q data could be accessed directly from the Realtek RTL2832U digital TV tuner chip, allowing it to be turned into a wideband software defined radio receiver with just a little extra hardware and softare.
Combined with a tuner front-end (commonly the Rafael Micro R820T2) in a USB dongle package with dinky antenna, these now show up in droves online for under $20.
I picked a random RTL2832U+R820T2 USB2.0 device from a seller on aliexpress. Like most, it is marketed primarily as a DAB/HDTV receiver, but first thing I did was throw away the Windows-only software provided, as I was more interested in the device as a broad-spectrum SDR receiver.
I’ve tried two MacOSX-compatible open source packages - Gqrx SDR and CubicSDR. Success with both! I’m liking CubicSDR in particular.
The other thing I learned is that the dinky 5” aerial provided with the dongle (and where I put it) is on the one hand surprisingly capable, while also having very little chance of picking out weaker signals!
As always, all notes, schematics and code are in the Little Electronics & Arduino Projects repo on GitHub
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LEAP#350 Drawing Circuits with CircuitScribe
There seems to have been quite a boom in conductive paint/ink applications in recent years. From the (google) research I’ve done, I haven’t found any particular reason for “why now” .. no great materials breakthough seems to be driving the trend. Perhaps it is more a market-pull situation - more people interested in wearables and flexible tech for example.
When I saw the latest Circuit Scribe kickstarter campaign, it was a perfect opportunity to try some out.
I received a simple LiteWings kit recently, and was impressed. After making the wing kits I still have ink in the pen, so now looking for novel applications;-)
As always, all notes, schematics and code are in the Little Electronics & Arduino Projects repo on GitHub
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LEAP#349 BURN a new demo for the Stringy
So, a long time after building the Boldport Club String, I decided to read the source .. and discovered I totally missed the fact that it has a demo mode!
I started out reading the source to learn more about the tricks James Hutchby used to implement the Karplus-Strong algorithm, but I was quickly distracted and decided first to make some new demo tracks..
After first confirming I could burn the original source, and of course wanting to avoid trascribing by hand in assembler, I got this workflow going:
Guitar Pro > MusicXML > stringyfi Ruby gem > MPLAB X IDE > PICkit 3 > Stringy!
As always, all notes, schematics and code are in the Little Electronics & Arduino Projects repo on GitHub
Here’s the new demo in action..
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LEAP#348 D Latch with NAND gates
The gated D latch is perhaps the fundamental 1-bit memory unit in active digital logic.
There are a few ways of constructing a D latch, here I’m using a NAND gate SR latch as the base, which is convenient as all it requires is a single 74LS00 (quad two-input NAND).
As always, all notes, schematics and code are in the Little Electronics & Arduino Projects repo on GitHub
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