All in all, the best code software for the iPhone”

Great application to get ready for the main event [Field Day]“

Overall a great program to practice morse code on the go

Thank you to everyone who has purchased the app and put a review on the iTunes site. A few things have cropped up in terms of features, functionality, etc. and I thought I’d comment on some of these here.

• 25wpm speed limitation – I have increased this to 50wpm and hope to send this update to the app store this week
• User Interface – Tapping the knobs to turn them, rather than touch & drag to turn. I agree this is not as intuitive as one would like, I have every intention of changing this so you can touch a knob and drag it either way to turn it clockwise or anticlockwise. For the first iteration it was simpler to use a button to make the knobs turn but this isnt what I want for the long term, particularly now that the speed goes up to 50.
• Ability to practice sending morse – Currently the app is just for practicing receiving code rather than giving you the ability to practice sending code by tapping on the screen. I do have a bunch of ideas along these lines but I needed to get the receive part done first.
• Info/settings button – The (i) button is hard to hit at times and this is a known bug. I’m using a standard Apple button and I need to increase the active area for that button to solve this problem. Alternatively moving it away from the edge of the screen might help
• Text size – I could add in an option to configure the font size, this makes a lot of sense. Making more room for the text on the screen might help too – perhaps an option to show/hide the controls or an alternative view when you rotate the iPhone to a landscape view?

I will be looking at the other issues raised as I make these changes. There was a suggestion to add more complex audio features (QRM, etc.) to make copying the code more realistic and this sounds like a great idea but I’ll need to do some reading on how to create those types of audio features on the iPhone.

Thanks again for the great support and I’ll keep working to improve the app so it meets everyone’s needs.

Simon, AA9PW.

A quick recap – to make sound you need to make a sound wave. For morse code this is usually a simple sine wave with a frequency somewhere around 600-800 Hz. To make morse code out of this you need to modulate it to make the dits and dahs, typically by turning the sound on and off as appropriate. If you are making this digitally (vs modulating a RF carrier frequency) you write your code so that there is silence when you want no sound and then when you need to have a dit or a dah you start the sine wave at the beginning of the dit/dah and then stop it after the appropriate length of time.

How long is an appropriate length of time? Well, the wikipedia page on morse code explains this all rather well but basically the timing works out to be one dit (in ms) = 1200/(desired code speed in words per minute). So, at 15 wpm, this works out to be 1200/15 = 80ms per dit. A dah is three times the length of a dit so that makes it 240ms long. There’s a one dit-length silence between each part of a letter (eg. between the dit and the dah of the character A), a three dit-length silence between characters in the same word and a seven dit-length silence between words. Throw all that together along with a translation table between the letters in your piece of text and the morse code needed for those letters and you are off and running.

Skipping over a bunch of bits for now (see a great explanation by Walt Fair Jr., W5ALT if you want more info), I’ve written code that gets this done on the iPhone and tested it on the iPhone Simulator that Apple provides for you to test your application. It sounds great, the audio waveform looks like this when I record the sound coming out of the computer’s speaker into Audacity.

Once things are working on the simulator you can connect your iPhone and run the same code on the actual device. When I do this and listen to the audio that comes out of the phone’s speakers, its not quite so nice, when you record the audio into audacity here’s what it looks like:

Not so pretty as before and while the audio still sounds passable, its clearly not as it should be. My challenge at the moment is to figure out why this is going on! The wave looks a bit like another sine wave is being added to the main one, causing the regular distortion observed but I cant for the life of me see where that is creeping in. I get the same distortion via headphones so I dont think its the speakers, I’ve made the audio mono to see if one of the stero channels was out of phase and causing the problem, this had no effect. When I look at the numerical values being created in the code, it should be making a nice smooth sine wave but…

This is the entertainment that is software development! I am currently waiting for the “Duh!” moment to occur where upon I will add back the missing semi-colon and everything will work as planned. Until that happens, if anyone has any suggestions I’d be very interested to hear them – I’m hoping that my fellow hams who are used to looking at wave forms and harmonics and things can get me pointed in the right direction.

Cheers!

Simon, AA9PW