Interfaces

1
Interfaces

• Points where your product and the outside world
  come together
• Human (User) Interface
• For most products, the most crucial part
• Includes displays, buttons, knobs, switches,
  look-and-feel
• Machine Interfaces
• Methods of communicating with other machines
• Electronic
• Mechanical

2
User Interfaces

• How does a human interact with your product?
• Goals
• Complete All functions can be controlled
• Comprehensible User can figure out how to
  successfully interact with your product
• Easy to learn Can do the above easily
• Multicultural/Multilingual
• Mechanically easy to use
• Lowest cost

3
Conflicting Interests

• Ease-of-learning
• Novice can pick up device and use it
• No user training needed
• Full descriptions of all features provided
• Can abort and back out of mistakes

• Ease-of-use
• Quick operation
• Few keystrokes/button presses
• No need to look at device to use it

4
Visual Distinguishers

• Distinguishers In prioritized order
• Label/Icon
• What is the function of this button?
• Avoid making new icons. Use only established
  international symbols.
• Location
• Important functions up front and center
• Group related items together
• Shape/Size
• Crucial functions (i.e. STOP) may have special
  size/shape
• Color
• Not a good distinguisher
• Use only in addition to other distinguishers

5
Mechanical Guidelines

• Consistency
• All buttons should be in the same area
• Power switch should be near other buttons
• Use the same type of buttons throughout
• Tactile feel
• Buttons should give tactile feedback when pressed
• Practical
• Avoid buttons that stick up far from the surface
• Buttons that stick far below the surface may
  conflict with internal components
• Changing the batteries is a UI issue!

6
Displays

• General-purpose
• LCDs
• ASCII Easy to use, generic
• Graphic More versatile, but harder to program
• Custom Hard to use, but cheaper in the long run
• VFDs
• Special-purpose
• LEDs
• Indicate high-priority needs
• May draw attention to primary display
• Seven-Segment LEDs
• Used when numerical data is primary purpose

7
Machine Interfaces

• What non-human devices does your system work
  with?
• Computers
• Storage devices
• Other similar instruments
• Batteries
• Power source
• Calibrating instruments

8
Data Interfaces

• Communication of data to other devices
• Standard protocols for communication
• RS232, USB, Firewire, PCMCIA
• Documentation and specification
• All protocols must have high-level spec
• Ex Sending the character G over the serial
  line will start the download of data
• Ex Computer will respond by sending all the data
  in packets of this form

9
Analog Interfaces

• Analog interfaces must be robustly designed
• Static protection
• Over-voltage protection
• Over-current protection
• Insulation
• Often a front-end is used that provided isolation
  of internal signals from external

10
Mechanical interfaces

• Batteries
• Where do they go?
• How are they serviced?
• Other external devices
• How do they interface?
• How is interface maintained?