Launchpad Serial Morse Code Transmitter


LaunchPad dev boards from Texas Instruments are cheap and easy to program, making them a great Arduino alternative if you can do without some of the bells and whistles. [ech0s] put his to good use by constructing a Morse code transmitter with dual operating modes. The transmitter can not only encode and transmit messages entered in a terminal client, it also allows the user to send messages by manually operating the key switch. Inspired by the high altitude balloon transmitter we featured last summer, this project uses similar components for signal amplification and transmission. Text can be entered in a Putty terminal window, which then is encoded into Morse by the MCU before transmission. At the moment, the speed of the radio transmission is about 15 WPM, which is reasonably quick. Even though his system performs quite well [ech0s] has some improvements planned, including having a proper PCB built as well as some software tweaks to improve buffering and bandwidth. Be sure to check out his video of the transmitter in action after the jump.


11 thoughts on “Launchpad Serial Morse Code Transmitter

  1. Anyone else annoyed with all the poor quality instructables links?

    It is a bad sign when the morse keyer doesn’t even get the morse code right. I had to stop te video after hearing both “O” and “W” incorrectly coded.

    Then there’s the issue with a “ham” transmitter that can’t even bother to transmit in the ham band. This is just so wrong. I don’t mind kids toying with ultra low power CW, amateur radio operators should be to a higher standard.

    I don’t want to just complain, so here’s an idea for a CW hack: Find a microcontroller and crystal that operate at a (legal) frequency of your choice and use the built in oscillator as your frequency base, driving a CMOS AND gate with it and an output pin of the microcontroller. That would be cool.

  2. My questions would be (a) longevity of the battery and (b) the ability to sustain a useful/stable sequence over a long period of time. I work with 10 meter propagation beacons that could benefit from something like this, but the keyer absolutely has to be “set and forget”.

    A lot of the DIY kits I’ve seen use EEPROMS, and will run on a 9V battery for upwards of a year, while keeping the WPM steady for the entire time.

    I personally use an old 386 laptop running a DOS program that keys the radio via serial port. It is a bit more power hungry (but the batteries are charged with a solar panel), but the WPM is “stable enough”, while giving me the ability to change the outgoing message fairly quickly.

    KD0GZJ/B, 28.2824 MHZ

  3. @ Ken

    The project uses an Oscillator in the 10/12m (24/28 MHz) Ham band, and NOT the microcontroller clock frequency. The oscillator is just driven by an output of the launchpad

    I am still practicing morse code so I can’t comment on the video much.

    Also, 15 WPM seems a bit slow for a computerized morse code transmitter – that’s about average speed for an experienced operator (in the past you were REQUIRED to send at that speed minimum for certain license classes and copy CW even FASTER!)
    look up the Jay Leno footage of Morse Code Vs. Cell phone keyboard SMS, CW kicks the cell user’s butt!

    73!, ke5tuz, Jimmy

  4. @Jimmy
    Ken is right, I’m using a 24.0 Mhz oscillator and I’m out of band (12m band is from 24.890 to 24.990 MHz). I’m deeply sorry for this but I only had that oscillator in my toolbox and I couldn’t find a good one without spending lots of money in shipping.(I’ve also written this in the instructable)

    You’re right on the mispelled “o”, I have to debug this because in the code I’ve defined the letter rightly. For me the “w” is good… Please note that I’m using an online receiver in the video, and there is a 9s lag. (I’m a beginner in ham radio and I can’t afford a receiver). I’ll try your idea, thanks for the suggestion!

    I’ll let you know as soon as I legalize this tx for continuous operation and battery longevity.

  5. @ech0s — take a look at ebay #370373314106. The Degen 1103 is a great little receiver, good sensitivity, picks up 100-29999KHz, and is cheap (you can actually find it less expensive than this auction — I picked mine up for $30 bucks shipped). Also, grab the Degen active antenna that is often sold with it (~$5)

    I’ve used the Degen 1103 ever since my Realistic DX-440 wore out (used weekly for radiofax, CW, and FEC reception since 1990!). Another good receiver, except it is a little pricey given the age of the available units now.

  6. Jimmy: Hopefully I didn’t sound too mean (though I do hate the instructables site). Building your own tools is a great way to learn morse code, and I support your goal. Think about connecting the transmitter directly to your receiver’s antenna input (through a big resistor) so you don’t transmit out of the ham bands.

    I double checked, and the “W” in “how” is rendered as dit-dah-dit, morse code for “R”. There was at least one more mistake, so double check the whole alphabet.

    By the way, I recently soldered that impossibly tiny 32768Hz crystal to a launchpad. Had to use a loupe (high power magnifying glass) to even see the leads with my middle aged eyes. I don’t know how, but it worked first try.

    asheets: An msp430 should be able to key a CW transmitter for well over a year on a watch battery. Active mode current drain is listed at 45microamps per MHz super low voltage msp430 devices. That’s 1.5 uA at 32kHz – 40 years on a CR3032 under idealized condition. One year with a common MSP430 should be easy to achieve, especially is power down modes are used. Just be sure you don’t suck too much power from the I/O pins (e.g. drive an FET switch instead of using the pin to power the xmit oscillator.

  7. This transmitter is also most likely not legal because there is no output filter. If it puts out a square wave at the output frequency, there are harmonics that are being transmitted that are out of band.

    So not only is the fundamental frequency wrong (24 mhz), it is also transmitting at multiples of that frequency most likely at a higher level that allowed even if the fundamental frequency was within the 12 meter band.

    Here is a PDF that has output filters that can be added without doing any of the math:

    I hope no one actually puts this transmitter on the air without making it legal.

  8. Thank you all for your suggestions!

    As I said, I’m a beginner in Ham Radio, I still don’t have a call.
    This TX was nothing more than a demo, I know I’m out of law with this TX (by the way I live in Region 1, but the band plan is similar).

    I was in a hurry for the Sparkfun Instructables contest, otherwise I would have taken my time developing it and published this on my blog.

  9. What always amazes me is the “that’s not legal” crowd lecturing people about every little interpretation of some regulation on the books. And how important it is to obey said laws.

    Yet, these same people probably think nothing of hopping in their cars and zooming down the highway doing 10-15 mph over posted speed limits. Or violating a host of other traffic laws.

    Heck, on the local repeater. One a-hole was reprimanding another ham over “illegal” operation of 10 meter amps on CB. Meanwhile, he’s proudly stating how he’s doing 80 mph (in a 65mph zone), and just managed to avoid a state trooper doing radar.

    To all the hypocrites quoting “laws” – STFU !!!

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