AmboVent: Low memory available, stability problems may occur

When I build the project for the Arduino Nano I see the following output in the Arduino IDE:

Sketch uses 18280 bytes (59%) of program storage space. Maximum is 30720 bytes.
Global variables use 1882 bytes (91%) of dynamic memory, leaving 166 bytes for local variables. Maximum is 2048 bytes.
Low memory available, stability problems may occur.

This is a problem, as it means the stack is nearly completely used up by global variables, so local variables in any scope or code section could potentially overflow the stack really easily. I think I can do some code cleanup to fix this, perhaps by moving strings to progmem with the F() macro, or using other coding techniques. I’ll have a look at the code.

Read more on the F() macro here:

1. https://www.arduino.cc/reference/tr/language/variables/utilities/progmem/
2. https://www.baldengineer.com/arduino-f-macro.html

UPDATE 20 APR 2020:

The bulk of this issue is resolved now that the two big lookup tables in the code are in progmem, but let’s still not close this issue until at least all strings have been surrounded by the F() macro and all large const arrays or structs (if any) have been moved to progmem.

• all string literals are inside an F() macro
• all large arrays or large data types (> ~16 bytes or so) are in PROGMEM)