A Framework For Making Affordable & Stylish Modular Controllers (USB to MIDI, HID, or Serial)

Step 3 Getting Familiar With Teensy++

The diagram above explains the Teensy++ pin configuration. You need to understand how these pins differ. 

Digital pins
All numbered pins on the Teensy++ board can be used as digital inputs/outputs. A digital pin is simply an on/off pin. It can be on (HIGH) or off (LOW). We use digital pins as input to read pushbuttons, or as outputs to turn LEDs on. 

PWM pins (14,15,16,24,25,26)
Pulse width modulation (PWM) means we can send a variable voltage out of that pin between 0 volts and 5 volts. PWM pins are ideal for LEDs as they allow us to vary the brightness of the LED. 

Interrupt pins (0,1,2,3,6,7,36,37)
Each pin with 'INT' is an interrupt pin. Interrupt pins are important cause we need them to read encoders. They are simply digital pins which have special functions attached to them and will notify the Teensy when their value has changed. The Teensy++ board has 8 interrupt pins, allowing you to read four encoders. 

Analog input pins (A0-A7)
Analog pins allow you to read variable voltages between 0 volts and 5 volts. We use analog pins to read potentiometers. These pins can also be used as digital inputs if specified (although I haven't yet tested this). 

+5V/GND
In the top right corner we have power (+5V) and in the top left we have ground (GND). All Components will need to use ground, and all analog components will need to use both ground and power.

I2C pins (0,1)
The I2C pins (SDA, SCL) are what we use to enable module->module communication. When module->module communication is enabled these two pins can no longer be used by a rotary encoder.

Other
Pin 6 is not used cause it already has an internal LED attached to it. Bottom pins (+5V, GND, RST) are not used, nor are the two side pins GND and AREF.

Internal pins (28-35,36,37)
Pins 28-37 are located internally on the board. These pins are digital.