Move pinStructs array into PROGMEM to save global variables space

[brewmanz]

This reduces the global variable space used.
Please check everything, as I'm using only a tiny fraction of FastGPIO in my code.
The generated code seems to be the same.
My test code was

      typedef FastGPIO::Pin<LED_BUILTIN> fastLED;
      for(int ix = 0; ix < aunit::TestRunner::gFailedOrExpiredTestCount; ++ix){ // maybe patch with large-ish number
        fastLED::setInputPulledUp();
        delay(150);
        fastLED::setOutputHigh();
        delay(200);
        fastLED::setInputPulledUp();
        delay(150);
        fastLED::setInput();
        delay(150);
      }

[DavidEGrayson]

What kind of environment are you using and how are you building your project? I would expect pinStructs to be garbage collected at link time because it is not needed by the code emitted by the compiler.

[brewmanz]

I'm using the Arduino IDE 1.8.20 under Ubuntu 20.04 LTS.
Aha! And I am referencing pinStructs in my sketch.

On compiling for Arduino Nano with my changes, my last 2 lines of compiler output states
Sketch uses 14260 bytes (46%) of program storage space. Maximum is 30720 bytes. Global variables use 568 bytes (27%) of dynamic memory, leaving 1480 bytes for local variables. Maximum is 2048 bytes.
when accessing FastGPIO::pinStructs,
and when NOT accessing FastGPIO::pinStructs it states
Sketch uses 14164 bytes (46%) of program storage space. Maximum is 30720 bytes. Global variables use 568 bytes (27%) of dynamic memory, leaving 1480 bytes for local variables. Maximum is 2048 bytes.
So accessing pinStructs uses extra Flash, but no extra RAM

I then roll back my changes, recompile, and it states
Sketch uses 14260 bytes (46%) of program storage space. Maximum is 30720 bytes. Global variables use 656 bytes (32%) of dynamic memory, leaving 1392 bytes for local variables. Maximum is 2048 bytes.
when accessing FastGPIO::pinStructs,
and when NOT accessing FastGPIO::pinStructs it states
Sketch uses 14164 bytes (46%) of program storage space. Maximum is 30720 bytes. Global variables use 568 bytes (27%) of dynamic memory, leaving 1480 bytes for local variables. Maximum is 2048 bytes.
So accessing pinStructs uses extra Flash, AND extra RAM

One reason for using pinStructs is to dynamically use a variable pin number to enable code like
FastGPIO::pinStructs[someDynamicPin]::setOutputHigh()
which I haven't done yet, but will very soon.