Arduino and Nano info from one idiot to other newbies :-)

I thought i would add some information that i learned along my path to working with Arduinos in general and Nanos as embedded parts of a KiCAD PCB in particular. I hope others find this helpful. Many thanks to “#BlackCoffee” who,along with others on the Arduino forum, helped me along.

Arduino schematic and PCB library elements are out there and work great. I’d be careful to get them from known sources, such as major supply houses, or he Arduino forums.

  1. Note that arduino pin numbering can be ambiguous. They have various sets of nomenclatures by which you refer to pins when programming - eg “D11” or “A2”. These are NOT THE SAME as the IC pin numbers when plugging a NANO (on soldered headers) into a PCB. Physical pins are numbered traditionally, beginning in the corner with P1, and working your way up one side and back down the other, 30 in total. Pay attention.

  2. Corollary to that: don’t do what I did! The physical pin numbers 1-30 are not how you define pins in your sketch. Rather, in the sketch, pins take on different numbers depending on the function (digital, analog, GPIO, …) you are using them for. This allows abstraction so on sketch works on UNOs, NANOs, Mega, …but fouled me up but good for a while. Silly me, i thought if i defined “Pin 2” as an input, and connected a PCB trace to the 2nd pin on the DIP package it would work. But in reality “Pin 2” for a digitalRead is in fact the 6th pin from the origin on the DIP package :frowning:

  3. 90% of the non-genuine Arduinos you buy will use a different USB/serial chipset (“CH340”) and demand the driver for that chip. This is almost always required on MACOS, sometimes on Windows. It can be found here:

  1. The better clones work very well. I bought clones off Amazon that came assembled on a board with header pins. work great. About $15/shipped for 3.

The Elegoo clones also work very well, but cost more.

  1. Careful with pin current. The pins drive an absolute maximum of 40mA. I hate to go more than 50% of rating, but an existing design drives a 27mA pin (continuous, 24x7) and runs totally cool. So…

  2. Careful with power. If you read carefully, all is clear but here are many power pins.

+5V after regulator. Intended to drive other things. OK to use if you have a very good regulated 5.0V supply. No protection.

+3.3V to drive external chips and sensors

Power in - input before onboard regulator and protection. Primary method to power. 7Vdc – 12 Vdc; but ideally why make it drop a lot of power? ~ 8-9Vdc raw is ideal.

USB power - 5V from your serial connection, protection diode drops it to 4.7V working. No issues in general

  1. The Arduino community is a great source of help and sketches.

  2. There are libraries for everything. Documentation varies from very good to “what documentation?” HOWEVER, there are example sketches in almost every library and once installed exist in the IDE menu. This is your best source of “how to” documentation.

Enjoy. No magic here.

Edit Jan 28th mostly typos, a few adds, no changes



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