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Project Notes

Arduino Notes

Timers and Pins

  • Timer0 - Used for millis and delay; also analogWrite/PWM on pins 5 and 6
  • Timer1 - analogWrite/PWM functions on pins 9 and 10; Servo library; Tone library (second tone)
  • Timer2 - analogWrite/PWM functions on pins 3 and 11; Tone library (first tone)

Tone library

  • On a standard Arduino board, the first tone will use timer 2 (so PWM on pins 9 and 10 will not be available);
  • the second tone uses timer 1 (preventing the Servo library and PWM on pins 11 and 12 from working).
  • On a Mega board, each simultaneous tone will use timers in the following order: 2, 3, 4, 5, 1, 0.”

Servo Library

  • The Servo library uses the same timer as analogWrite on pins 9 and 10, so you can’t use analogWrite with these pins when using the Servo library.


DIP Pins

The atmega328_pins

Arduino Pro Mini

USB-to-Serial Programming

Pin Connections as described on weworkweplay:

  • Connect USB DTR to Arduino GRN, aka DAW on some boards
  • Connect USB RXD to Arduino TXD
  • Connect USB TXD to Arduino RXI
  • Connect USB 3.3V to Arduino VCC
  • Connect USB Ground to Arduino BLK, aka GND on some boards

The pro_mini_usb_serial_connection

Arduino Nano

See the Official Arduino Nano site for board details.



  • Operating Voltage (logic level) 5 V
  • Input Voltage (recommended) 7-12 V
  • Input Voltage (limits) 6-20 V

The power source is automatically selected to the highest voltage source from one of:

  • the Mini-B USB connection
  • 6-20V unregulated external power supply (pin 30)
  • 5V regulated external power supply (pin 27)

See also:


The nano_pins



Project Source on GitHub Project Gallery Return to the LEAP Catalog

This page is a web-friendly rendering of my project notes shared in the LEAP GitHub repository.

LEAP is just my personal collection of projects. Two main themes have emerged in recent years, sometimes combined:

  • electronics - usually involving an Arduino or other microprocessor in one way or another. Some are full-blown projects, while many are trivial breadboard experiments, intended to learn and explore something interesting
  • scale modelling - I caught the bug after deciding to build a Harrier during covid to demonstrate an electronic jet engine simulation. Let the fun begin..
To be honest, I haven't quite figured out if these two interests belong in the same GitHub repo or not. But for now - they are all here!

Projects are often inspired by things found wild on the net, or ideas from the many great electronics and scale modelling podcasts and YouTube channels. Feel free to borrow liberally, and if you spot any issues do let me know (or send a PR!). See the individual projects for credits where due.