my recent reads..

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!

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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 hero_image


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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 hero_image

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.

Gated_D_latch_symbol

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 hero_image


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