Uno Shield 0

Uno Shield 0 starts with a SparkFun Joystick Shield Kit, then adds audio output and a rotary encoder.

Audio Output

By capturing the RX and TX signals and feeding them into a small speaker, we can give the user an audible indication of download activity. The setup() function can also emit a beep when it starts up. Finally, the loop() function can emit sounds (e.g., clicks, tones) to indicate control activity, settings, etc.

Between these, the user should be able to:

• determine that the Arduino is running
• track current modes and settings
• monitor the results of a sketch
• interact with a running sketch

Components

This section covers most of the major components.

Joystick Shield

The SparkFun Joystick Shield Kit has four large buttons, arranged in a diamond pattern, and a small button (to reset the Arduino). It also has a small (tiltable and clickable) joystick and a "prototyping" area with lots of convenient holes.

Other Controls

Rotary encoders (some with built-in push switches) are economically available on eBay. These can be used to implement menu systems, etc. I'm also adding four potentiometers, to provide settable analog voltages and adjust the PWM time constants.

Speakers

I'm using a 3.5 mm (1/8") switched stereo phone connector to provide audio for an external speaker, headphones, etc. I may also add a small speaker or two, for convenience.

Input Jack

I'm using another switched 3.5 mm connector to allow sampling of two (slow!) audio-level (1 V P-P) input channels. This could be used to measure voltages or slow-moving analog signals, either from an external source or (by default) internal PWM-enabled digital pins.

Exercises

This shield should be versatile enough to allow a variety of exercises. Here is a small sampling, to get us started:

Analog Inputs

ADCs 0 & 1 can detect analog voltage levels produced by the joystick. Vertical and horizontal tilt affect ADC0 and ADC1, respectively.

• Measure and report these voltages.

ADCs 2 & 3 can detect voltages produced by potentiometers 0 & 1. Digital pins 6 & 7, when used as AIN0 and AIN1, can be used to compare these voltages.

• Measure and report these voltages.

• Compare and report these voltages.

ADCs 4 & 5 can detect voltages from the 1/8" stereo input jack. If both this jack and the output jack are unoccupied, they can detect (PWM) analog levels generated by digital pins 9 & 10. (Potentiometers 2 & 3 determine the time constants.)

• Measure and report these voltages.

• Measure and report the settling time.

Digital Output

Pins 9 & 10 can be cycled to produce (say) square waves in the left and right channels of the Out Jack.

• Generate the same tone in both channels.

• Vary the amplitude and pitch, using the joystick.

• Vary the pitch, using the rotary encoder.

• Toggle the encoder between amplitude and pitch,
  using its push switch.

• Generate a stereo pair of tones in Ionian mode.

• Use the buttons to change the generated mode.

Pin Usage

This section describes our use of the Uno's pins. Keep the Uno Pin Usage page handy as a reference!

Default

By default, the Joystick Shield uses the following pins:

Set	Pin	Function(s)	Usage
Analog	A0	ADC0	Joystick (Vertical)
Analog	A1	ADC1	Joystick (Horizontal)
Digital	D2	INT0	Joystick (Select)
Digital	D3	INT1	Button (Right)
Digital	D4		Button (Top)
Digital	D5		Button (Bottom)
Digital	D6		Button (Left)
_	RESET		Button (Reset)

As Hacked

In an ideal world, we would simply add our own use cases. However, the existing pin assignments get in the way of things we'd like to do. So, we need to hack the wiring, moving some of the pin assignments around. The current plan is to do this by means of jumpers (aka "blue wires"), which re-route signals (e.g., from circuit board holes to different device pins).

The table below indicates these hacks in the change (C) column. Pins are unchanged (_), added (A) or moved (M) pins, as needed:

Set	Pin	Mode	Usage	C
Analog	A0	ADC0	Joystick (Vertical)	_
Analog	A1	ADC1	Joystick (Horizontal)	_
Analog	A2	ADC2	Potentiometer 0	A
Analog	A3	ADC3	Potentiometer 1	A
Analog	A4	ADC4	In Jack (Right)	A
Analog	A5	ADC5	In Jack (Left)	A
Digital	D2	INT0	Encoder (Select)	A
Digital	D3	INT1	Encoder (Pin A)	A
Digital	D4		Encoder (Pin B)	A
Digital	D5		Button (Bottom)	_
Digital	D6	AIN0	Potentiometer 0	A
Digital	D7	AIN1	Potentiometer 1	A
Digital	D8		Joystick (Select)	M
Digital	D9	PWM	Out Jack (Right)	A
Digital	D10	PWM	Out Jack (Left)	A
Digital	D11		Button (Top)	M
Digital	D12		Button (Right)	M
Digital	D13		Button (Left)	M
_	RESET		Button (Reset)	_

Notes

D9 & D10 are only used for output. They can be used to generate audio tones (via digital waveforms) or analog (PWM) levels.

The remaining pins are only used for input. Pins A0-A6 measure voltages (e.g., potentiometer settings). Pins D6 & D7 are used for the analog comparator. The rest are used to detect buttons, encoder rotation and select, and joystick select.

• A2 and A3 can each measure a DC voltage level.
  We provide these via Potentiometers 0 & 1.

• D2 and D3 have vectored interrupts. The encoder
  needs these; the Joystick and Right button don't.

• D5 and D6 (AINx) can compare two DC voltages.
  We provide these via Potentiometers 0 & 1.
  D5 can also be set up to count button presses.

• D9 and D10 can generate DC voltages, via PWM.
  These are routed (via Potentiometers 2 & 3) to the
  Out Jack and the NC contacts of the In Jack.

Resources

• SparkFun
  • Joystick Shield Kit
    • Circuit Diagram
    • GitHub Page

• Changing PWM Frequency on the Arduino

• Analog-to-digital_converter
• Arduino
• Joystick
• Jumper
• Phone Connector
• Potentiometer
• Pulse-width modulation
• Rotary encoder

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This wiki page is maintained by Rich Morin, an independent consultant specializing in software design, development, and documentation. Please feel free to email comments, inquiries, suggestions, etc!