Notes about USB and Bluetooth hardware accessories.
While the app must not require any external hardware, it is an advantage to have external input devices which emulate on-screen button presses particularly in cases when the operator needs to be carefully observing something momentary such as pilot passing a timing gate and can't be looking at the touch-screen of the device at the same time.
By far the most common input will be some kind of make or break switching action which can be converted into a digital USB input with a simple keyboard emulator. Same thing can be used to manage input from automatic switching devices eg timing gate sensors or kick-stick sensors.
For this, there must be an external input protocol so the app knows what to do with keystroke inputs from devices.
h5. Protocol option a
* Task requires a stopwatch-like ability (start, stop, lap, reset)
* A hardware device such as a button box sends unusual keystrokes to the app, eg on this device the green button sends ctrl-A.
* Task setup file includes an instruction that if keystroke ctrl-A is received, this means press 'start' button on screen.
*Advantage*: Means a button press can mean different things in different tasks.
*Disadvantage*: Operators may have different button boxes, red button on this one sends ctrl-A, but that one sends ctrl-Z
h5. Protocol option b
* Task requires a stopwatch-like ability (start, stop, lap, reset)
* A library of keypress meanings is established where it is known that ctrl-A always means timer start.
*Advantage*: No setup configuration needed (ie a timer component in the app is hard coded to know that if ctrl-A is received this always means stopwatch-start). Transparent support of different devices.
*Disadvantage*: Means a physical device eg button box will either have only one purpose, (eg stopwatch) or needs some more complex switching ability to convert between 'modes', ie in mode a (stopwatch) a green button press sends ctrl-A but switch it to mode b (counter) and a green button press sends ctrl-X which in the common protocol means increment current count by one.
h5. Best option?
Despite its disadvantages, Option a is probably the most flexible, is simpler to control settings in software than hardware. A list of 'recommended' button presses could be published so it would be 'normal' for a green button to always send ctrl-A and that means start timer (of a stopwatch), increment by 1 (of a counter) Etc.
h5. Cheap and simple keyboard emulators (eg for button boxes)
* [teensy|http://www.pjrc.com/teensy/usb_keyboard.html]
* [U-hid|http://www.u-hid.com/home/index.php]
* [I-Pac|http://www.ultimarc.com/ipac1.html]
* [Reverse engineer an old keyboard|http://runawaybrainz.blogspot.co.uk/2012/01/hack-reverse-engineer-and-re-purpose.html]
While the app must not require any external hardware, it is an advantage to have external input devices which emulate on-screen button presses particularly in cases when the operator needs to be carefully observing something momentary such as pilot passing a timing gate and can't be looking at the touch-screen of the device at the same time.
By far the most common input will be some kind of make or break switching action which can be converted into a digital USB input with a simple keyboard emulator. Same thing can be used to manage input from automatic switching devices eg timing gate sensors or kick-stick sensors.
For this, there must be an external input protocol so the app knows what to do with keystroke inputs from devices.
h5. Protocol option a
* Task requires a stopwatch-like ability (start, stop, lap, reset)
* A hardware device such as a button box sends unusual keystrokes to the app, eg on this device the green button sends ctrl-A.
* Task setup file includes an instruction that if keystroke ctrl-A is received, this means press 'start' button on screen.
*Advantage*: Means a button press can mean different things in different tasks.
*Disadvantage*: Operators may have different button boxes, red button on this one sends ctrl-A, but that one sends ctrl-Z
h5. Protocol option b
* Task requires a stopwatch-like ability (start, stop, lap, reset)
* A library of keypress meanings is established where it is known that ctrl-A always means timer start.
*Advantage*: No setup configuration needed (ie a timer component in the app is hard coded to know that if ctrl-A is received this always means stopwatch-start). Transparent support of different devices.
*Disadvantage*: Means a physical device eg button box will either have only one purpose, (eg stopwatch) or needs some more complex switching ability to convert between 'modes', ie in mode a (stopwatch) a green button press sends ctrl-A but switch it to mode b (counter) and a green button press sends ctrl-X which in the common protocol means increment current count by one.
h5. Best option?
Despite its disadvantages, Option a is probably the most flexible, is simpler to control settings in software than hardware. A list of 'recommended' button presses could be published so it would be 'normal' for a green button to always send ctrl-A and that means start timer (of a stopwatch), increment by 1 (of a counter) Etc.
h5. Cheap and simple keyboard emulators (eg for button boxes)
* [teensy|http://www.pjrc.com/teensy/usb_keyboard.html]
* [U-hid|http://www.u-hid.com/home/index.php]
* [I-Pac|http://www.ultimarc.com/ipac1.html]
* [Reverse engineer an old keyboard|http://runawaybrainz.blogspot.co.uk/2012/01/hack-reverse-engineer-and-re-purpose.html]