Hello
I am an Arduino novice and its been a year or two since I dabbled with it . I have decided to pick a project up again with a fresh start .
I am looking for a board that is small , has 4 external interrupts and ideally is 5v . The nano every looks to fit .
My issue is looking on the Arduino site the "specs" for this board vary on every page they are on . One says its 16mhz , other say 20 . Another place says I/O pins have a 15Ma current , others 20. The input votage varies across the sites also , is 21v a typo on 12v ??
Some of these do not matter to me but I need 13 digital output pins with 4 being interrupts . The crunch is they all seem to imply 22 D I/O pins . So this is how much of a novice I am , are the analouge pins used as digital pins ? As the board layout only shows 13 . I seem to recall from my old mini boards the rx and tx are used as d0 and d1 .
The conflicting info is a little frustration for someone like me that does not readly know what they are doing .
Different board designs. 16 versus 20 MHz is the choice of crystal or resonator fuse setting used for the MCU clock. The choice of voltage regulator dictates the maximum input voltage on Vin.
Another place says I/O pins have a 15Ma current , others 20
Those are simply different opinions on the maximum safe current flow. The ATmega4809 data sheet gives an absolute maximum of 40 mA, and you would be wise to stay well under that.
Good choice of a Nano Every. I have used them in many projects.
They are very different from the classic Nano and more capable. The internal processer registers are very different, and any original Nano programs which call directly call register addresses/names will need modification.
The system clock is a choice you can make in your program or from a boards.txt file. It's not a function of some fixed external crystal oscillator but rather an internal oscillator which can be run at either 16 or 20 MHz.
The input voltage varies across the sites also , is 21v a typo on 12v ??
No it is indeed 21v. The Nano Every using a switching input voltage regulator
The analog pins can be used as digital pins. The Tx and Rx pins on D0/D1 are a separate hardware serial port addressed as Serial1 and is separate from the usb serial. Those pins can also be used as general digital pins.
If you are going to use a Nano Every, I would recommend that you use MegaCoreX instead of the megaavr Arduino designed core. It has more features and is better maintained.
As a general rule, you can remember that each pin can support 20mA. And each pin offers full interupt functionality. If you install the MegaCoreX package, all options are open to you with an additional serial interface and free use of timer TCA.
The original Arduino Nano Every Board is set to 16MHz. You can change this from x to 20MHz because the internal clock generator is used. Most of this is possible via changes in registers at runtime. Few settings are only possible by changing the fuse.
Thanks for the replys . I have had the project running on a early board of this size but it only had two interupts , part of the upgrade is possibly using these , alas I need 4 . The only other main issue was the input voltage , if they could only take 12v I would have to improve my voltage input circuit to cap it , its in a car so voltage variance with the alt etc .
I will add MegaCoreX to the things I need to read up on , its a growing list .