Using a Raspberry Pi and LED to send morse code to a smartphone | Hacker News Reader

Using a Raspberry Pi and LED to send morse code to a smartphone

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43 pointsonli13 comments

As an aside from the OP, and because I think it would be of interest to the developers here on HN: I had to learn Morse code decades ago when I was in flying school. I did it the old, rote method, which sort of worked.

I knew that the series of dots and dashes were based on the frequency of the letters (shorter codes for more frequently used letters etc.)

It is only recently that I discovered that the Morse code can be expressed in terms of a Binary Tree, based on that same frequency of letters [0], with dots to the left and dashes to the right.

This 'new' way of thinking about the code would make a far easier task of trying to remember the codes, I believe, as the tree is really only 4 levels deep (if you ignore numbers on the 5th level, which have their own consecutive pattern anyway).

[0] - https://www.mathworks.com/content/dam/mathworks/mathworks-do...

The difficult part isn't knowing which symbol is which. The problem with learning the tree, or rote memorization, is that you'll learn it as a translation table. This will slow you down to well below conversational speed. You'll "know" morse, but in practice you won't be able to use it. I think that's what you were implying with "sort of worked"?

(To be clear, I'm not saying that you can't learn morse code at all that way, and definitely not suggesting that you are or aren't fluent in it.)

For a really great modern approach, see https://experiments.withgoogle.com/collection/morse (no hardware needed, just a smartphone).

In general the recommendation is not to learn that dit, dah, dah, dit means letter "P" (and you already know what sound P has), but directly learn that the sound "ditdahdahdit" corresponds to the sound of "P". And thus cut out the middle step.

There are a few more things to actually using morse:

* Clean timing

* Keying (straight keys aren't used anymore. sideswipes / dual lever are somewhat intuitive. iambic keying is not, but it's so much less exhausting.)

* Head copy (the challenge is understanding entire words/phrases, without paper, and/or buffering it in your head because writing down char by char is too slow)

* Dealing with noise (incl other morse conversations)

(This is coming from a ham radio perspective, so maybe a bit different than flying school. I'm really curious now - did you actually expect to use it back then, or was this a case of mostly learning for the test? If yes, in what situation and how? ie, would you actually use a morse key? In the airplane? Or was it more about something like recorded emergency messages or similar?)

For aviation this is getting very dated in the US. Even when I learnt to fly 20+ years ago we didn’t need it, Eveyobe had a GPS. But anyways charts had this:

https://www.cfinotebook.net/graphics/avionics-and-instrument...

Basically if you had a pen paper you could just write down the Morse code then compare it to the chart. Speed wasn’t of the upmost importance. And this is assuming the VOR was lacking voice capability.

For more information on using a VOR:

http://www.cfinotebook.net/notebook/avionics-and-instruments...

UK as I understood it was less fond of voice, and favored NDB and Morse....

Thanks for your input. To answer your questions at the end - Yes, we learned it primarily for the test, but also this was more than 20 years ago, and back then, the ATIS (Terminal Information System) broadcast that gave you your weather and QNH etc. would prefix every repeated recorded broadcast with the 4 letter ICAO airport code.

My local airport here is YPDN (Darwin, Australia), but in larger cities with several airports, we had to verify via morse to the instructor during a flight test that we had dialled in the correct ATIS frequency by cross checking the morse ICAO code.

Also, we had to do the same verification when dialling in to an NDB (Non Directional Beacon) which is about the most basic navaid available on a plane. Because the ADF (Automatic Direction Finder) on board used to dial into an NDB was in the HF radio band and thus subject to reflections off the troposphere inadvertently picking up another NDB over the horizon, we also had to listen to the repeated morse identifier of that beacon to ensure we had dialled in and were tracking the correct one.

As said, only on flight tests mainly. We soon got used to the patterns of the beacons and transmissions that we used regularly and would just listen for the pattern rather than try and decipher each letter/number.

EDIT: Here is a video I found recently which talks about using the binary tree method of memorising morse code, as well as another method - https://www.youtube.com/watch?v=D8tPkb98Fkk

Thank you, that was very interesting!

In particular how reflections caused you trouble, whereas in the ham world (also mostly HF) the same are desirable because anything that increases range is generally seen as good (we do use directional antennas to narrow it down). Different world.

And so in the end, you did learn to recognize entire words (callsigns) at once :-)

Nice. Reminds me of a "Using a Raspberry Pi to send and receive Morse Code with a laser" post from a while ago [1].

[1] https://partofthething.com/thoughts/sending-and-receiving-mo...

Knowing a little Morse code, the scene in Stranger Things where they set up a whole wall of letters was mildly infuriating. I guess if no parties knew the code that's what you'd have to do. But what a great reason to learn!

Ham radio operators still use it (they call it CW for continuous wave) mostly because it is really easy to hear over super long distances (inter-continental) with small radio equipment (often just a few Watts) through all the noise.

FWIW, here is a CW beacon I built using RF circuitry and an AT Mega 388:

https://youtu.be/YaaSstm3qP4

I focused on the morse part in the title of this submission, but just for a lack of a good way to include the rest. The technical details and the use case are interesting, but I really liked the framing of it as well. Doing what you love doing and actually being able to earn money that way.

Christmas 2013 I received both a raspberry kit and a toy Star Trek phaser, so I managed to make a Morse Code transcribing toy phaser. Can't seem to find the video but it was a fun way to spend a lazy holiday afternoon.

I came across a similar concept earlier this week https://youtu.be/sdgnX49ZXig

Was he signalling Batman, or what?

> It’s used on a really large field where they fly drones and don’t allow any radio communications except the drone controllers. Turns out there are apps that will read Morse code signals sent on light by cell phones!

I gave it two solid skims and missed that both times, thanks!

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