Alligator Pads & Pinout

Don't feel like you have to understand this part fully! Skim it for now, and consider it a resource for you when you want to take a deeper dive into understanding the hardware!

There are 14 total Alligator Pads on the outside of the Circuit Playground. These are for you when you want to add more sensors or circuitry without the need for soldering. Use any kind of alligator clip (the small ones work best but any size should be able to grip onto the pads)

Capacitive Touch

All 8 non-power pads (e.g. not the GND/3.3V/VBATT) around the Circuit Playground have the ability to act as capacitive touch pads. Each pad has a 1 MΩ resistor between it and digital pin #30. You can toggle this pin in your sketch to control whether the resistor is a pullup or pulldown or floating. Note that this means that all the pads have a 2 MΩ resistance between them, not important for 99% of uses but may be confusing for some cases where you are trying to detect very high resistance values

Library Reference

You can get the capacitance reading from a pin using CircuitPlayground.readCap(pin) and just set the pin to any of the pad #'s next to the pad (e.g. 0, 1, 2, 3, 6, 9, 10 and 12) The number returned will vary from about 0 to about 1000. Any reading above approximately 50 will correspond to a touch, but it does depend a bit on what material and length is connected to the pin so you will need to adjust your code based on your setup.

Pad Usage (pinout)

We'll use terminology like analog inputs, PWM outputs, interrupts, I2C, UART etc. We'll cover all this later, just know you can use this list for reference!

Left Side

Starting from the Micro USB jack and going clockwise here are what the pins do.

  • 3.3V - this is the output from the onboard 3.3V power supply. This is the main power voltage for the 'Play but can also be used to power sensors, GPS or bluetooth modules, etc. You can draw a maximum of 500mA. See the Battery Jack & Supply page for more details
  • #10 - this is connected to the microcontroller's pin #10. This pin can also be used for analog inputs and is called A10. It can also act as a PWM output.
  • #9 - this is connected to the microcontroller's pin #9. This pin can also be used for analog inputs and is called A9. It can also act as a PWM output.
  • GND - shorthand for Ground you'll need to this when powering or connecting to external devices.
  • #6 - this is connected to the microcontroller's pin #6. This pin can also be used for analog inputs and is called A7. It can also act as a PWM output.
  • #12 - this is connected to the microcontroller's pin #12. This pin can also be used for analog inputs and is called A11. It can also act as a PWM output.
  • VBATT - this is the battery voltage output from whichever is higher: the JST battery pack or USB. It cannot be used as a power input! It is designed to power high-current or high-voltage devices that need more like 5V than 3.3V. If connected to USB, this pin provides 5V. If powered from battery, the output voltage will vary depending on the battery pack.

Right Side

Starting from the Micro USB jack and going counter-clockwise here are what the pins do.

  • GND - Same as the other Ground pins
  • SCL #3 - This is a special-purpose pin. It is connected to the microcontroller's pin #3. This pin can also act as a PWM output and an interrupt input (INT0). The other special usage is connecting to I2C sensors and devices, as the I2C Clock pin
  • SDA #2 - This is a special-purpose pin. It is connected to the microcontroller's pin #2. This pin can also act as a PWM output and an interrupt input (INT1). The other special usage is connecting to I2C sensors and devices, as the I2C Data pin
  • 3.3V - Same as the other 3.3V power supply pins
  • RX #0 - This is a special-purpose pin. It is connected to the microcontroller's pin #0. This pin can also act as an interrupt input (INT2). The other special usage is connecting to UART/Serial sensors and devices, as the Data Receive (RX) pin.
  • TX #1 - This is a special-purpose pin. It is connected to the microcontroller's pin #1. This pin can also act as an interrupt input (INT3). The other special usage is connecting to UART/Serial sensors and devices, as the Data Transmit (TX) pin.
  • GND - Same as the other Ground pins
Last updated on 2016-07-18 at 10.48.52 PM Published on 2016-07-19 at 08.31.23 PM