User Interfaces and Usability for Embedded Systems

Feedback to 'Put the User in the Driver's Seat' - Embedded Systems Design, Aug 2006

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I enjoyed your article on putting the user in the driverís seat. I work on video gaming machines (mostly video slot machines) and I think the user interface can really affect how well the games perform. More serious gamblers, especially in Eastern Europe and Asian countries demand features that the casual gambler doesnít want to use. So you have to make these features available and easy to use if desired, but pretty much transparent, and hard to accidentally activate to the more casual gamblers. Game times are typically 2.5 Ė 3.5 seconds a game, so while this is isnít safety critical or managing a complex device like an airplane or even a car, you still need to make things very obvious and not slow down the serious player, while making it difficult for a novice player to accidentally enable a feature that may cost them more money than they expected. Iím not sure if youíve tried either of these, but since you mentioned remotes and running watches in your articleÖ

On the 3 remotes to watch tv. I just bought a Logitech Harmony 676 remote and was able to put all 5 of my remotes in a drawer and havenít used them since. Itís activity based so you push a button for the activity you want (listen to radio, CD, watch a DVD, watch TV, or Cable, or HDTVÖ) and then the remote maps the buttons to control the appropriate devices. My only real complaint is the remote remembers the last state of all the devices, so if you manually adjust anything, it may be confused about what devices are on, which inputs are enabledÖ. It has a nice help system to walk you through straightening this out pretty quickly, but you have to tell the kids to never manually adjust things, and it just seems wrong to have to do this.

On the watch for running, if you havenít tried one, you might want to look at a Garmin Forerunner. A GPS might be overkill when going out for a run, but you just hit the start button when you start out, and the stop button when youíre done. It gives you the distance, current pace, and elapsed time on the display (you can customize it, but I havenít needed to). It stores a history of all your runs (or bike rides), and some models will download the data to your pc via serial or USB port. You can have it auto-pause the timer if youíve stopped running to allow for traffic lights, and to automatically beep at each mile or km and display your split times. I got separated from a group during a run along a pretty twisty out and back course for the first time, and while still running turned on the navigation feature for the first time, and was able to use it to find my way back, without having to stop running or having read the manual. Since the new models are now out, you could probably pick up a new Forerunner 101 for around $70, or maybe a bit less.


Niall's response

Working on usability for gambling machines probably added the interesting property that most extra features can be measured in exact financial return, which will make it a much more measurable design than you would have in design's where you have to conduct user surveys or trials to judge success.

During a recent product upgrade, I was told that customers didn't like the dial on our existing product to change values. It is speed-sensitive, to increase by either 10 or 100 for one revolution, and has a good-sized aluminum knob with a finger indent so it spins quite well. Some values range from 1 to 10,000 and require an input resolution of 1. If a customer wants to increase a value by 200, they usually have to twiddle the dial back and forth to get the exact value. The new product has up/down/left/right/select buttons. Left-right selects the digit, up/down increments and decrements (with rollover to next higher digit).

My concern with a numeric keypad involves max-min limits and the resolution of some values. Some input values have resolutions of 2, 5, or 25 (ignoring decimal places). For example, only 0, 5, 10, 15, ... may be legal values. If someone enters "7", what is the proper reaction - round up, or round down, or change to a warning screen and force the user to re-enter a value? A similar issue arises with max-min limits, probably the best solution being a warning screen showing the limit and allowing the user to accept the limit value or change the value and enter.

With the left/right/up/down numerical entry, values can change by 1, 2, 5, or 25 with a single push of a button, a value of 7 cannot be entered, and values stop at limits. When the increment is 25, two digits are highlighted, so the change to two digits with one push is more obvious.

Any non-numerical values allow the user to select from a text list, e.g. Fast/Medium/Slow using the up/down buttons.

Ed Barney, Vermont, USA

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