I wrote Datac in 2011 as an aid for a colleague of mine, Radek Domín who was looking to capture automotive performance data using an Apple iOS device such as an iPhone or iPad (or a suitable Android device). As I had some experience with iPhone development on my iPhone 3GS, I volunteered to help with signal acquisition on the iOS devices. All of the code for the application was written by me, except where noted below.
The app takes in a signal from the device's mic (internal or headphone jack) and displays it in the main display. It also takes samples of the data and performs some filtering and detection algorithms in order to determine the vehicle's current RPM. The data capture component was heavily influenced by Apple sample code that worked with CoreAudio, in particular custom render procedures for AudioUnit nodes.
Here is a screen capture of the input view. Note that this view is rendered using OpenGL.
There are three indicators at the top:
- Connection - illuminated if there is an external headphone/microphone attached
- Record - button that starts/stops recording of the input signal
- Power - button that toggles the emission of a high-frequency sine wave. Can be used to drive suitable low-power devices.
In the default mode, the Input view shows audio values from -1 to +1 on the Y axis with time on the X axis. You can zoom in by pinch-expand gesture. In a zoomed state, you can pan the view around by a touch-and-drag gesture.
To freeze the view, simply tap once on it. Tap again to resume the view updates.
Here is a screen capture of the detections view. The plotting here is done via the CorePlot framework.
The original usage for this application was to monitor RPM signals coming from a device that hooked in to a automobile's onboard computer. The Detections tab shows a graph of such signal detections. For other purposes, you are of course free to customize the view or to eliminate it entirely.
You can make a recording of the signal input as an audio file (WAV or CoreAudio format) and these files can then be transfered to a Mac via iTunes or to a Dropbox folder.
The application used to be available on Apple's App Store, but unfortunately got dropped when I changed my account from US to Czech Republic. The code repository was originaly hosted on GoogleCode but with its pending demise I moved it over to Github.
The RPM plots rely on the CorePlot framework to do all of the heavy lifting. It is a very nice collection of classes that render wonderful graphs with all of the eye-candy you want. Getting it to work properly with Datac's tabbed interface took some doing, especially when stressed with orientation rotations, but it is nonetheless an excellent framework that is only getting better.
For application settings, there is nothing better than the InAppSettingsKit (IASK) by Luc Vandal and Ortwin Gentz. Incredibly versatile collection of classes that track and extend how Apple's Settings application does it work, while giving the programmer the ability to do the setting editing all from within the application, without having to exit and jump over to the Settings app. Even better, IASK supports different setting definitions depending on where the editing occurs and on what type of iOS device it is done one.
The integration with Dropbox was done in a day using their great SDK package, available to all for free after registering. I did have to add a way to cancel an active file upload, but everything else is straight from the SDK. In short, Dropbox is an incredibly easy way to make available data generated on an iOS device, without having to waiting for an iTunes connection some time in the future.
I created all of the application icons and images using the fantastic Opacity application. It is not free, but it is worth every bit of its very-reasonable price. I especially like the integration with Xcode and the automatic generation of icons of varying sizes from the same master. It is an incredible times-aver.
If you find this software useful, I'd appreciate a note saying so.
The application used to be available on Apple's App Store, but unfortunately got dropped when I changed my account from US to Czech Republic. The code repository was originaly hosted on GoogleCode but with its pending demise I moved it over to Github.