added support for gray-scale images

Added support for gray scale images on mono-color LED matrices.

Author: michaelkamprath

CHANGELOG.md

@@ -7,15 +7,17 @@ and this project adheres to [Semantic Versioning](http://semver.org/spec/v2.0.0.
 ## [Unreleased]
 
 ### Changed
-- Refactored the image classes to have a common, templated base class. This consolidates similar logic to a single location.
+- Refactored the image classes to have a common, templated base class. This consolidates similar logic to a single location. This caused the existing Glyph object to have it's API slightly changed.
+- Improved interrupt handling on 8-bit AVR microcontrollers
 
 ### Added
 - Support for the Arduino Zero and Due boards (and related)
 - Support for older ATmega8535, ATmega16 and ATmega32 microcontrollers
 - Support for ATmega1284 and ATmega1284P microcontrollers
 - A method to LEDImage for drawing circles
 - A Red-Blue-Green bit layout mode for the RGB matrix object
-- An option to shift out an "all off" signal for a short period of time in between row updates to the shift registers. This helps mitigate LEF ghosting when the time to turn off for the row power switch is appreciable and cannot be mitigated in hardware. For example, when using 2981 source drivers for the row power switching.
+- An option to shift out an "all off" signal for a short period of time in between row updates to the shift registers. This helps mitigate LED ghosting when the time to turn off for the row power switch is appreciable and cannot be mitigated in hardware. For example, when using 2981 source drivers for the row power switching, which requires 2 microseconds to turn off.
+- Added support for a "gray scale" LED matrix. This is a mono-color LED matrix where PWM is used to effect varying intensity in each LED. 
 
 
 ## [1.0.1] - 2017-12-24

keywords.txt

@@ -11,6 +11,9 @@ Frame				KEYWORD1
 Glyph				KEYWORD1
 GlyphBase			KEYWORD1
 GlyphSequenceAnimation	KEYWORD1
+GrayScaleColorType	KEYWORD1
+GrayScaleImage		KEYWORD1
+GrayScaleLEDMatrix	KEYWORD1
 ImageSequenceAnimation	KEYWORD1
 LEDMatrix			KEYWORD1
 LEDMatrixBits		KEYWORD1
@@ -69,3 +72,10 @@ YELLOW_COLOR		LITERAL1
 INDIVIDUAL_LEDS		LITERAL1
 RGB_GROUPS			LITERAL1
 RBG_GROUPS			LITERAL1
+
+GRAYSCALE_BLACK			LITERAL1
+GRAYSCALE_DARK_GRAY		LITERAL1
+GRAYSCALE_LIGHT_GRAY	LITERAL1
+GRAYSCALE_MEDIUM_GRAY	LITERAL1
+GRAYSCALE_TRANSPARENT	LITERAL1
+GRAYSCALE_WHITE			LITERAL1

library.properties

@@ -1,10 +1,10 @@
 name=Shift Register LED Matrix Lib
-version=1.0.1
+version=1.1.0
 author=Michael Kamprath <michael@kamprath.net>
 maintainer=Michael Kamprath <michael@kamprath.net>
 sentence=A driver for LED matrices that use shift registers to control rows and columns. 
 paragraph=Provides a high level API for managing and drawing to the LED matrix. Can drive either a single color or RGB LED matrices. Color shading is enabled using PWM-style updates to the matrix shift registers. Uses a clock interrupt. Designed to be used with 74HC595 and/or DM13A type shift registers, or similar. See website for hardware designs supported.
 category=Display
 url=http://www.kamprath.net/led-matrix/
 architectures=*
-includes=LEDMatrix.h,RGBLEDMatrix.h,RGBImage.h,Glyph.h,RGBAnimation.h,RGBAnimationSequence.h,TimerAction.h
+includes=LEDMatrix.h,GrayScaleLEDMatrix.h,RGBLEDMatrix.h,GrayScaleImage.h,RGBImage.h,Glyph.h,RGBAnimation.h,RGBAnimationSequence.h,TimerAction.h

src/BaseLEDMatrix.cpp

@@ -19,10 +19,6 @@
 #include "BaseLEDMatrix.h"
 #include "SRLEDMatrixUtils.h"
 
-#ifndef ICACHE_RAM_ATTR
-#define ICACHE_RAM_ATTR
-#endif
-
 const unsigned long UPDATE_INTERVAL = 2000;
 
 static BaseLEDMatrix* gSingleton = NULL;
@@ -448,12 +444,12 @@ void TC3_Handler()                              // Interrupt Service Routine (IS
 // scan timing. 
 //
 
-#define BASE_SCAN_TIMER_INTERVALS 12
+#define BASE_SCAN_TIMER_INTERVALS 24
 
 void BaseLEDMatrix::startScanning(void) {
 	this->setup();
 
-	_interFrameOffTimeInterval = max(257 - (BASE_SCAN_TIMER_INTERVALS/5)*_interFrameOffTimeMicros, 0);
+	_interFrameOffTimeInterval = max(255 - _interFrameOffTimeMicros, 0);
 
 	noInterrupts(); // disable all interrupts
 
@@ -468,13 +464,13 @@ void BaseLEDMatrix::startScanning(void) {
 	// overflow only mode
 	TIMSK2 &= ~(1<<OCIE2A);
 
-	// configure to fire about every 5 micro-second 
-	TCCR2B |= (1<<CS22) ; 
-	TCCR2B &= ~(1<<CS20);
-	TCCR2B &= ~(1<<CS21);
+	// configure prescaler to /32 
+	TCCR2B |= (1<<CS20);
+	TCCR2B |= (1<<CS21);
+	TCCR2B &= ~(1<<CS22) ; 
 
 	// load counter start point and enable the timer
-	TCNT2 = this->nextRowScanTimerInterval();
+	TCNT2 = 0; // max interval for first timer fire
 	TIMSK2 |= (1<<TOIE2);
 
   	interrupts(); // enable all interrupts
@@ -485,6 +481,7 @@ void BaseLEDMatrix::stopScanning(void) {
 }
 
 unsigned int BaseLEDMatrix::nextRowScanTimerInterval(void) const {
+	// this yields multiple of 50 microseconds on a 16 MHz chip
 	return  max(257 - this->baseIntervalMultiplier( _scanPass )*BASE_SCAN_TIMER_INTERVALS, 0 );
 }
 

src/BaseLEDMatrix.h

@@ -25,6 +25,10 @@
 
 #define LED_MATRIX_MAX_SCAN_PASS_COUNT 1
 
+#ifndef ICACHE_RAM_ATTR
+#define ICACHE_RAM_ATTR
+#endif
+
 class BaseLEDMatrix : public TimerAction {
 
 private:
@@ -84,7 +88,9 @@ class BaseLEDMatrix : public TimerAction {
 	 *				 be waited until the next row update gets shifted out. Usually a value 
 	 *				 less than 3 microseconds is sufficient for most slow row power
 	 *				 switching.
-	 *  @param slavePin which ard pin is used for the latch signal.
+	 *  @param slavePin which pin is used for the latch signal.
+	 *  @param maxSPISpeed The requested max SPI speed. The board typically picks the 
+	 *				smaller of this and it's own max.
 	 */
 	BaseLEDMatrix(
 			unsigned int rows,