Morse code Bluetooth keyboard

My previous attempt at a Morse code keyboard worked over USB and used a copper coin as a capacitive sensor. Since then I've acquired a real telegraph key and Adafruit's Bluefruit EZ-Key board. With that and a Trinket I made a Morse code Bluetooth keyboard. It works with any computer that has Bluetooth (also phones and tablets).



Here's what it looks like in action (as usual please excuse my lack of Morse code skills):



Here's the Arduino sketch that's running on the Trinket. As before there's a buzzer for feedback and the transmission speed is fixed.

If you're into Morse code, I continue to recommend my Android application that listens to Morse code using your smartphone's microphone and translates it to text.

Here's a diagram of the connections:

Morse code USB keyboard

Further exploring the capabilities of Arduino Micro as an input device, I made a telegraph key that works as a regular USB keyboard. Here's a demonstration (please excuse my lack of Morse code skills):



For the input part I used the CapacitiveSensor library. The way it works is there's a send pin and a receive pin. You put a resistor between the two pins (I used 1 megaohm) and then also connect a piece of metal to the receive pin that will act as the sensor that you touch. I used a copper coin soldered to a piece of wire. (One serious limitation of capacitive sensing done this way is that the Arduino needs to be grounded, so for example it may not work well with battery-powered laptops.)

I also added a buzzer for feedback, the one I used makes a sound when the signal pin is driven low.

Here's the sketch that's running on the Arduino. As you can see the transmission speed is fixed (though it wouldn't be hard to make it adapt to the observed speed).

If you're a Morse code enthusiast, I also recommend my Android application that listens to Morse code using your smartphone's microphone and translates it to text.

Morse Code Reader

I wanted to make a Morse code reading application for some time now. Here's my first attempt, it listens to the signal through the phone's mic and translates it to text:



I'm sure there are all kinds of advanced signal processing techniques that I should be using, but for now I went with the simplest, most naive approach. And it sort of works, except when it doesn't. What I do is I keep an exponential moving average of the signal's volume and I decide that the signal is currently "high" when the average is above a threshold and "low" when it's below it. The threshold is set based on recent peak volume. Then I try to decide what the length of a dot and a dash is, interpret the input accordingly, and finally translate the dots and dashes to letters. The application adapts to changing volume and speed within reasonable limits (it should work up to about 40 WPM).



I was hesitant about putting the application on Android Market, as I only tested it on my phone and it quite often fails at translating Morse code. Then again, it's not like I have anything to lose by getting 1-star reviews and insulting comments, so why not.

Here's a Market link.