Editing Microcontroller User Interfaces

The intent of this page is to document different styles of user interfaces for microcontrollers together with code ( any language ) to drive them.  We could use some contributions, can you help?

== Input ==

In principal any sensor can be used as an input so you may want to look at information on sensors as well.  These are the ones that are easy for people to manipulate.


=== Momentary Button ===
*Pro  Cheap, simple, uses only 1 bit port
*Con  If you use a bunch uses a lot of port bits
*Find Code at:

=== Toggle switch ===
*Pro  Self indicating, not too expensive.
*Con  Not very flexible unless used for binary input.
*Find Code at:

=== Rotary Switch ===
*Pro
*Con
*Find Code at:

Can be self decoding: position of switch indicates state of microcontroller.

=== Rotary Encoder ===
*Pro  2 wire interface.
*Con  Code a bit complex, needs interrupt processing or fast polling.
*Find Code at:

=== Potentiometer ===
Use to feed a voltage to an analog to digitial converter.  You sould be able to get quite a few discrete values out of this while still having it easy to use.  Instead of a pot you can use a rotary switch with fixed resistors switched.  

*Pro    Uses only 1 pin if using an AtoD converter.
*Con    Readint takes a AtoD converter ( or standard io port(s) with software.  Takes a bit of time.

=== Keypad ===
*Pro
*Con

=== TV remote control and IR remote receiver ===
* Pro: lots of pretty buttons, relatively low-cost -- under $2 for the IR remote receiver module, then use TV remote control you already have or a $10 remote; uses only 1 port pin
* Con: may be difficult to program and debug; you never know when the batteries will die.

== Output ==

=== Single Led ===

In its simplest form either on or off, slightly harder to read are various patterns of blinks.

* Pro: easiest to program and lowest-cost user interface: from under $.10 for a tiny LED to a few dollars for a high-intensity LED. Can "read" from all the way across the room.
* Con: only shows 1 bit of information at a time

=== Multiple Led ===

*Pro Cheap, simple, easy to drive.  One port bit per led ( untill you get to large numbers where ticks kick in )  Match with a pushbutton and state of the microcontroller and means to change it is simple.
* Con: Can use more port bits than you have. Some LEDs may be dimmer than others. Uses more power than most other user interfaces.

A shift register can make driving a large number of LEDs easier.

=== POV display ===

[[POV display]]
* Pro: learning experience; easy to make large displays
* Con: uses more power than most other user interfaces; complicated and difficult to debug; can hurt you.

=== 7 Segment Led ===
: ''main: [[Basic Circuit Building Blocks#Seven segment LEDs]]''

* Pro: All segments matched brightness and packaged nicely.
* Con: difficult to display letters

=== character LCD ===
In the nibble mode mode needs a total of 7 port bits.  Some displays are backlit, others are not.

* Pro: Can have lots of characters, small displays are often 2 x 16.  Cost is about 10 bucks. Perhaps the simplest and lowest-power way to display text.
*Con  Cost is about 10 bucks.  You may not have the 7 port bits available.

The Hitachi HD44780 parallel interface is extremely common on character LCDs.
In addition to displaying letters and digits,
the Hitachi HD44780 supports a few "user-defined characters" that support simple graphics,
such as the [http://wilsonminesco.com/multitask/ battery-life icon documented by Garth Wilson].

* ''(Many [[watch display]] are character LCDs)''
* [https://en.wikipedia.org/wiki/Hitachi_HD44780_LCD_controller Wikipedia: Hitachi HD44780 LCD controller]

=== graphical LCD or OLED ===
* Pro:
* Con:  graphics often fill up and overflow whatever memory you have available. The person programming the system often spends huge amounts of time tweaking the graphics.

: ''(Many [[watch display]] are graphical LCDs or OLEDs)''

=== PC on Serial Port ===
Control with a terminal program or a custom application.  PC provides both input and output.

*Pro 2 bit only.  Can have very fancy smart interface.  Can be very useful for debugging.
*Con Needs PC.  May need custom application. For good flexibility needs a uart on the chip.


[[category:Microcontroller]][[category:Serial Communications]]