Fix comments re: Arduino Mega, PROGMEM string in scrolltext example

Author: PaintYourDragon

RGBmatrixPanel.cpp

@@ -43,28 +43,26 @@ BSD license, all text above must be included in any redistribution.
 // be specified as any pin within a specific PORT register stated below.
 
 #if defined(__AVR_ATmega1280__) || defined(__AVR_ATmega2560__)
- // Arduino Mega hasn't actually been tested -- use at your own peril!
+ // Arduino Mega is now tested and confirmed, with the following caveats:
  // Because digital pins 2-7 don't map to a contiguous port register,
- // the Mega will require connecting the matrix data lines to different
- // pins.  Ports A, C, and L all offer the requisite contiguous 6 bits.
- // I wanted to use PORTL in order to keep the external memory interface
- // free, but accessing the upper PORT registers in assembly seems to
- // require some additional flaming hoops and doesn't work with the
- // inline code here.  PORTA is used instead (Mega pins 22-29, though
- // only 24-29 are actually connected to the LED matrix).  Clock may be
- // any pin on PORTB -- on the Mega, this CAN'T be pins 8 or 9 (these
- // are on PORTH), thus the wiring will need to be slightly different
- // than the tutorial's explanation on the Uno, etc.  Pins 10-13 are all
- // fair game for the clock, as are pins 50-53.
+ // the Mega requires connecting the matrix data lines to different pins.
+ // Digital pins 24-29 are used for the data interface, and 22 & 23 are
+ // unavailable for other outputs because the software needs to write to
+ // the full PORTA register for speed.  Clock may be any pin on PORTB --
+ // on the Mega, this CAN'T be pins 8 or 9 (these are on PORTH), thus the
+ // wiring will need to be slightly different than the tutorial's
+ // explanation on the Uno, etc.  Pins 10-13 are all fair game for the
+ // clock, as are pins 50-53.
  #define DATAPORT PORTA
  #define DATADIR  DDRA
  #define SCLKPORT PORTB
 #elif defined(__AVR_ATmega32U4__)
- // Arduino Leonardo is still a work in progress -- DO NOT USE!!!
- // Unlike the Uno, digital pins 2-7 do NOT map to a contiguous port
- // register, dashing our hopes for compatible wiring.  This is probably
- // going to require changes both to bit-shifting code in the library,
- // and how this board is wired to the LED matrix.  Bummer.
+ // Arduino Leonardo: this is vestigial code an unlikely to ever be
+ // finished -- DO NOT USE!!!  Unlike the Uno, digital pins 2-7 do NOT
+ // map to a contiguous port register, dashing our hopes for compatible
+ // wiring.  Making this work would require significant changes both to
+ // the bit-shifting code in the library, and how this board is wired to
+ // the LED matrix.  Bummer.
  #define DATAPORT PORTD
  #define DATADIR  DDRD
  #define SCLKPORT PORTB
@@ -75,6 +73,8 @@ BSD license, all text above must be included in any redistribution.
  #define SCLKPORT PORTB
 #endif
 
+#define nPlanes 4
+
 // The fact that the display driver interrupt stuff is tied to the
 // singular Timer1 doesn't really take well to object orientation with
 // multiple RGBmatrixPanel instances.  The solution at present is to
@@ -120,7 +120,6 @@ void RGBmatrixPanel::init(uint8_t rows, uint8_t a, uint8_t b, uint8_t c,
   addrbpin  = digitalPinToBitMask(b);
   addrcport = portOutputRegister(digitalPinToPort(c));
   addrcpin  = digitalPinToBitMask(c); 
-  nPlanes   = 4;     // Other code is fixed at 4 planes; don't change this
   plane     = nPlanes - 1;
   row       = nRows   - 1;
   swapflag  = false;
@@ -527,22 +526,24 @@ void RGBmatrixPanel::updateDisplay(void) {
     // A tiny bit of inline assembly is used; compiler doesn't pick
     // up on opportunity for post-increment addressing mode.
     // 5 instruction ticks per 'pew' = 160 ticks total
-    #define pew \
-      asm volatile("ld  __tmp_reg__,%a0+" :: "e"(ptr));                   \
-      asm volatile("out %0,__tmp_reg__" :: "I"(_SFR_IO_ADDR(DATAPORT)));  \
-      asm volatile("out %0,%1" :: "I"(_SFR_IO_ADDR(SCLKPORT)),"r"(tick)); \
-      asm volatile("out %0,%1" :: "I"(_SFR_IO_ADDR(SCLKPORT)),"r"(tock));
+    #define pew asm volatile(                 \
+      "ld  __tmp_reg__, %a[ptr]+"    "\n\t"   \
+      "out %[data]    , __tmp_reg__" "\n\t"   \
+      "out %[clk]     , %[tick]"     "\n\t"   \
+      "out %[clk]     , %[tock]"     "\n"     \
+      :: [ptr]  "e" (ptr),                    \
+         [data] "I" (_SFR_IO_ADDR(DATAPORT)), \
+         [clk]  "I" (_SFR_IO_ADDR(SCLKPORT)), \
+         [tick] "r" (tick),                   \
+         [tock] "r" (tock));
 
     // Loop is unrolled for speed:
     pew pew pew pew pew pew pew pew
     pew pew pew pew pew pew pew pew
     pew pew pew pew pew pew pew pew
     pew pew pew pew pew pew pew pew
 
-    // From the "Unsolved Mysteries" department: "buffptr += 32" doesn't
-    // work here, scrambles the display.  "buffptr = ptr" does, even though
-    // both should produce the same results.  Couldn't tell you why.
-    buffptr = ptr;
+    buffptr += 32;
 
   } else { // 920 ticks from TCNT1=0 (above) to end of function
 

RGBmatrixPanel.h

@@ -34,12 +34,12 @@ class RGBmatrixPanel : public Adafruit_GFX {
     Color888(uint8_t r, uint8_t g, uint8_t b, boolean gflag),
     ColorHSV(long hue, uint8_t sat, uint8_t val, boolean gflag);
 
-  // Printing
  private:
 
-  uint8_t *matrixbuff[2];
-  uint8_t nRows, nPlanes, backindex;
-  boolean swapflag;
+  uint8_t         *matrixbuff[2];
+  uint8_t          nRows;
+  volatile uint8_t backindex;
+  volatile boolean swapflag;
 
   // Init/alloc code common to both constructors:
   void init(uint8_t rows, uint8_t a, uint8_t b, uint8_t c,

examples/colorwheel_32x32/colorwheel_32x32.pde

@@ -11,15 +11,15 @@
 
 // If your 32x32 matrix has the SINGLE HEADER input,
 // use this pinout:
-#define CLK 8  // MUST be on PORTB!
+#define CLK 8  // MUST be on PORTB! (Use pin 11 on Mega)
 #define OE  9
 #define LAT 10
 #define A   A0
 #define B   A1
 #define C   A2
 #define D   A3
 // If your matrix has the DOUBLE HEADER input, use:
-//#define CLK 8  // MUST be on PORTB!
+//#define CLK 8  // MUST be on PORTB! (Use pin 11 on Mega)
 //#define LAT 9
 //#define OE  10
 //#define A   A3

examples/colorwheel_progmem_32x32/colorwheel_progmem_32x32.pde

@@ -15,15 +15,15 @@
 
 // If your 32x32 matrix has the SINGLE HEADER input,
 // use this pinout:
-#define CLK 8  // MUST be on PORTB!
+#define CLK 8  // MUST be on PORTB! (Use pin 11 on Mega)
 #define OE  9
 #define LAT 10
 #define A   A0
 #define B   A1
 #define C   A2
 #define D   A3
 // If your matrix has the DOUBLE HEADER input, use:
-//#define CLK 8  // MUST be on PORTB!
+//#define CLK 8  // MUST be on PORTB! (Use pin 11 on Mega)
 //#define LAT 9
 //#define OE  10
 //#define A   A3

examples/plasma_16x32/plasma_16x32.pde

@@ -10,7 +10,7 @@
 #include <Adafruit_GFX.h>   // Core graphics library
 #include <RGBmatrixPanel.h> // Hardware-specific library
 
-#define CLK 8  // MUST be on PORTB!
+#define CLK 8  // MUST be on PORTB! (Use pin 11 on Mega)
 #define LAT A3
 #define OE  9
 #define A   A0

examples/plasma_32x32/plasma_32x32.pde

@@ -12,15 +12,15 @@
 
 // If your 32x32 matrix has the SINGLE HEADER input,
 // use this pinout:
-#define CLK 8  // MUST be on PORTB!
+#define CLK 8  // MUST be on PORTB! (Use pin 11 on Mega)
 #define OE  9
 #define LAT 10
 #define A   A0
 #define B   A1
 #define C   A2
 #define D   A3
 // If your matrix has the DOUBLE HEADER input, use:
-//#define CLK 8  // MUST be on PORTB!
+//#define CLK 8  // MUST be on PORTB! (Use pin 11 on Mega)
 //#define LAT 9
 //#define OE  10
 //#define A   A3

examples/scrolltext_16x32/scrolltext_16x32.pde

@@ -9,7 +9,10 @@
 #include <Adafruit_GFX.h>   // Core graphics library
 #include <RGBmatrixPanel.h> // Hardware-specific library
 
-#define CLK 8  // MUST be on PORTB!
+// Similar to F(), but for PROGMEM string pointers rather than literals
+#define F2(progmem_ptr) (const __FlashStringHelper *)progmem_ptr
+
+#define CLK 8  // MUST be on PORTB! (Use pin 11 on Mega)
 #define LAT A3
 #define OE  9
 #define A   A0
@@ -19,11 +22,14 @@
 // buttery smooth animation.  Note that NOTHING WILL SHOW ON THE DISPLAY
 // until the first call to swapBuffers().  This is normal.
 RGBmatrixPanel matrix(A, B, C, CLK, LAT, OE, true);
+// Double-buffered mode consumes nearly all the RAM available on the
+// Arduino Uno -- only a handful of free bytes remain.  Even the
+// following string needs to go in PROGMEM:
 
-char   str[]   = "Adafruit 16x32 RGB LED Matrix";
+const char str[] PROGMEM = "Adafruit 16x32 RGB LED Matrix";
 int    textX   = matrix.width(),
-       textMin = sizeof(str) * -12;
-long   hue     = 0;
+       textMin = sizeof(str) * -12,
+       hue     = 0;
 int8_t ball[3][4] = {
   {  3,  0,  1,  1 }, // Initial X,Y pos & velocity for 3 bouncy balls
   { 17, 15,  1, -1 },
@@ -64,11 +70,12 @@ void loop() {
   // Draw big scrolly text on top
   matrix.setTextColor(matrix.ColorHSV(hue, 255, 255, true));
   matrix.setCursor(textX, 1);
-  matrix.print(str);
+  matrix.print(F2(str));
 
   // Move text left (w/wrap), increase hue
   if((--textX) < textMin) textX = matrix.width();
   hue += 7;
+  if(hue >= 1536) hue -= 1536;
 
   // Update display
   matrix.swapBuffers(false);

examples/testcolors_16x32/testcolors_16x32.pde

@@ -10,7 +10,7 @@
 #include <Adafruit_GFX.h>   // Core graphics library
 #include <RGBmatrixPanel.h> // Hardware-specific library
 
-#define CLK 8  // MUST be on PORTB!
+#define CLK 8  // MUST be on PORTB! (Use pin 11 on Mega)
 #define LAT A3
 #define OE  9
 #define A   A0

examples/testshapes_16x32/testshapes_16x32.pde

@@ -10,7 +10,7 @@
 #include <Adafruit_GFX.h>   // Core graphics library
 #include <RGBmatrixPanel.h> // Hardware-specific library
 
-#define CLK 8  // MUST be on PORTB!
+#define CLK 8  // MUST be on PORTB! (Use pin 11 on Mega)
 #define LAT A3
 #define OE  9
 #define A   A0

examples/testshapes_32x32/testshapes_32x32.pde

@@ -12,15 +12,15 @@
 
 // If your 32x32 matrix has the SINGLE HEADER input,
 // use this pinout:
-#define CLK 8  // MUST be on PORTB!
+#define CLK 8  // MUST be on PORTB! (Use pin 11 on Mega)
 #define OE  9
 #define LAT 10
 #define A   A0
 #define B   A1
 #define C   A2
 #define D   A3
 // If your matrix has the DOUBLE HEADER input, use:
-//#define CLK 8  // MUST be on PORTB!
+//#define CLK 8  // MUST be on PORTB! (Use pin 11 on Mega)
 //#define LAT 9
 //#define OE  10
 //#define A   A3