This is a quick start guide to code pedalSHIELD UNO. I am going to explain just the basic ideas you need to know to progress as fast as possible.


1. What Do You Need to Know About the Hardware?
You need to know how the hardware resources (leds, buttons, ADCs, PWMs) are mapped:



Inputs:
Digital_2: TOGGLE SWITCH.
Analog_4: PUSH-BUTTON_1.
Analog_5: PUSH-BUTTON_2.
Analog_0: GUITAR INPUT JACK.
Digital_12: TRUE-BYPASS FOOTSWITCH.

Outputs:
Digital_13: LED.
PWM_9 (Digital9): OUTPUT JACK.
PWM_10(Digital10): OUTPUT JACK.


2. Installing the Software.
The integrated development environment (IDE) software for Arduino UNO is needed. It is available in the Arduino Software page with all the instructions. There is also a getting started with Arduino UNO guide for more details.

Once all the software is installed the environment should look like this:




3. Start Coding!
There is a series of pedals already coded and available in the forum. All this effects have "educational" purposes. The idea is to have them as a base to start improving or coding your own effects, so the codes have a balance between performance and complexity so you can understand them easily.

Going from the easy to difficult, the natural evolution is:

Clean/Transparent pedal.
Volume/Booster pedal.
Distortion pedal.
Fuzz Distortion pedal.
Bit-Crusher pedal.
Daft Punk Octaver pedal.
Signal Generator pedal.
Metronome.
Delay pedal.
Tremolo pedal.

You can also download them all in a .zip file:
(I recommend to use the examples from the zip file because they are always up to date)

pedalshield_uno_pedal_examples.zip

There are also some good contributions in the forum, have a look to this cool codes:

• Variable Pitch Shift
• Multi-effects: Clean+Boost+Distortion+Fuzz+Cr​usher
• 7 new effects for pedalSHIELD UNO

what's the difference between distortion and fuzz distortion in programs?

as mention in the messages :

the distortion code cuts the upper limit when it reaches the threshold. The distortion in this case is asymmetrical (only clipped on one side).
The Fuzz code boosts the signal to max when it reaches the threshold (symmetrical).