LEAP#353 D Flip-Flop with NAND Gates
The D Flip-flip is the synchronous (clocked) sibling of the D latch.
There are various ways of constructing a D flip-flip from fundamental logic units, here I’m using only NAND gates. And there we have it - 1 bit of memory in a clocked register! It’s nice to see it work, even if this circuit is no longer of any real practical use.
As always, all notes, schematics and code are in the Little Electronics & Arduino Projects repo on GitHub
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LEAP#352 Decoding ACARS
Aircraft Communications Addressing and Reporting System (ACARS) is a short message digital datalink protocol transmitted around 129-137 MHz in different regions. As well has assisting air traffic control, it is (I gather) how services like flightaware get their data.
For a quick test, I’m using the open-source rtl_acars_ng. It built and ran on MacOSX without trouble, connecting to an R820T2+RTL2832U dongle.
As always, all notes, schematics and code are in the Little Electronics & Arduino Projects repo on GitHub
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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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