Added ASCII and string support for 7-segment backpack

[dmadison]

This swaps out the 7-segment hex-only table for a full ASCII character set, allowing the user to write alphanumeric characters and symbols in addition to hexadecimal values.

Like the alpha table, the 7-segment ASCII table is stored in flash memory. All digit display calls now pass through the writeDigitChar function, with decimal and hex characters in the pre-existing writeDigitNum now offset to their character equivalents. I've also added some overloaded print and println functions to write characters and strings to the display, left-justified. Behavior of the integer and float functions is unchanged.

This shouldn't break any pre-existing code unless it was accessing the numbertable array directly instead of through the class, as that has been replaced by the ASCII font table.

I've added a string print test to the sevenseg.ino example to demonstrate the string feature.

[K4stor]

Why u no merge this ? This awesome

[dmadison]

/home/runner/work/Adafruit_LED_Backpack/Adafruit_LED_Backpack/Adafruit_LEDBackpack.cpp:161: warning: documented symbol 'static const uint16_t alphafonttable' was not declared or defined.

I'm not sure what the CI is complaining about here. The array is defined in the source file and I don't see anything of note on line 161.

[caternuson]

@dmadison Hey, if you're still interested in working this PR, looks like the CI is failing on the doxygen part:

[dmadison]

After some more sleuthing it looks like Doxygen is getting confused with the PROGMEM keyword. Removing the keyword from the first of the two arrays (in either order) fixes the issue. Although that's certainly not a good fix for the board's memory.

On the Doxygen side this can be fixed by enabling macro expansion and adding PROGMEM to the list of predefined keywords in the Doxyfile:

MACRO_EXPANSION        = YES
PREDEFINED             = __cdecl= \
                         PROGMEM=

Unfortunately I'm not sure there's a good way around the issue without modifying the Doxyfile in some way.

[caternuson]

Ugh. What a weird doxy issue. I tried some stuff locally, and just relocating the PROGMEM modifer seemed to fix it as well. Try this:

static const PROGMEM uint8_t sevensegfonttable[] = {
static const PROGMEM uint16_t alphafonttable[] = {

[dmadison]

Hopefully that works! I've never seen the attribute placed before the variable, but it seems to compile fine on my machine.

[caternuson]

Now clang is unhappy. Looks like just some trailing whitespace. Here's how to install and run:
https://learn.adafruit.com/the-well-automated-arduino-library/formatting-with-clang-format

[dmadison]

Are the numeric base changes for char intentional? I'm not sure how that's supposed to be interpreted.

[dmadison]

Ah okay I see it - the removal of the bases for the char print types is something I changed for this pull request specifically, three years ago (2ff4d95). Merging from master reverted that change.

[caternuson]

Looks good. Gonna merge. Thanks for continuing to work this update!

Tested with:

#include "Adafruit_LEDBackpack.h"

Adafruit_7segment seg = Adafruit_7segment();

int count = 0;

void setup() { 
  seg.begin(0x70);

  for (uint8_t i='!'; i<='z'; i++) {
    seg.writeDigitAscii(0, i);
    seg.writeDigitAscii(1, i+1);
    seg.writeDigitAscii(3, i+2);
    seg.writeDigitAscii(4, i+3);
    seg.writeDisplay();
    delay(300);
  }

  seg.print(1000, DEC); seg.writeDisplay(); delay(1000);
  seg.print(0xBEEF, HEX); seg.writeDisplay(); delay(1000);
  seg.print(12.34); seg.writeDisplay(); delay(1000);
  seg.print("7SEG"); seg.writeDisplay(); delay(1000);

  for (uint16_t counter = 0; counter < 9999; counter++) {
    seg.println(counter);
    seg.writeDisplay();
    delay(10);
  }

  seg.print("YEAH");
  seg.writeDisplay(); 
}

void loop() {
}