1 # Using NanoEngine for systems with low resources
5 [tocstart]: # (toc start)
7 * [Introduction](#introduction)
8 * [Main idea of NanoEngine](#main-idea-of-nanoengine)
9 * [Simple NanoEngine demo](#simple-nanoengine-demo)
10 * [Reading keys with NanoEngine](#reading-keys-with-nanoengine)
11 * [Draw monochrome bitmap](#draw-monochrome-bitmap)
12 * [Draw moving bitmap](#draw-moving-bitmap)
13 * [What if not to use draw callbacks](#what-if-not-to-use-draw-callbacks)
14 * [Using Adafruit GFX with NanoEngine](#using-adafruit-gfx-with-nanoengine)
15 * [To upper level](@ref index)
19 <a name="introduction"></a>
22 Many applications use double-buffered output to physical display to avoid flickering effect, when a user observed non-completed picture for a short time. When working with color OLED/LCD displays like ssd1331, some micro-controllers do not have enough RAM to fit display buffer in. For example, in 8-bit mode ssd1331 OLED display needs 6144 bytes (`96*64`). But simple micro-controller like Atmega328 has only 2KiB, and Attiny85 has only 512B of RAM. But with ssd1306 library you still can create applications for those ones with good graphics.
23 ssd1306 library represents NanoEngine8, intended to be used with color OLED displays. Digit 8 means that engine implements 8-bit color mode. Refer to arkanoid8 as example, which can be run even on small Attiny85 with color ssd1331 display. The system supports NanoEngine1 for monochrome OLED displays, NanoEngine8 for 8-bit RGB OLED displays, NanoEngine16 for 16-bit RGB OLED displays.
25 <a name="main-idea-of-nanoengine"></a>
26 ## Main idea of NanoEngine
28 There are 2 issues with tiny controllers:
29 * they have a little RAM
30 * they support low frequencies
32 The first problem is solved in NanoEngine by using double-buffer to redraw only part of display content at once. By default NanoEngine uses 8x8 small buffer (64 bytes) and 24 bytes to store information on areas, which need to be refreshed.
33 The second problem is solved almost the same way: refresh only those part of display content, which were changed since last frame update. For example, ssd1331 oled display work on SPI at 8MHz frequency, that means in ideal conditions the screen content can be refreshed 162 times per second (`8000000/(96*64*8)`). But with the data, you need to send also commands to the display and to do some other stuff. And real tests with Atmega328p show that `ssd1306_clearScreen()` can run only at 58 FPS, coping data from buffer to OLED memory runs slower.
34 There is no such issue for Arduboy, since it uses monochrome OLED ssd1306 with only 1KiB of RAM buffer, and theoretical fps can be up to 976. For color display and small controllers the main solution is to refresh only part of display content. Arkanoid8 can give easily 60 fps with NanoEngine8
36 <a name="simple-nanoengine-demo"></a>
37 ## Simple NanoEngine demo
46 engine.canvas.clear();
47 engine.canvas.setColor(RGB_COLOR8(255,255,0));
48 engine.canvas.drawRect(15,12,70,55);
49 return true; // if to return false, the engine will skip this part of screen update
54 /* Init SPI 96x64 RBG oled. 3 - RESET, 4 - CS (can be omitted, oled CS must be pulled down), 5 - D/C */
55 ssd1331_96x64_spi_init(3, 4, 5);
58 engine.setFrameRate(30);
59 /* Set callback to draw parts, when NanoEngine8 asks */
60 engine.drawCallback( drawAll );
65 if (!engine.nextFrame()) return;
66 engine.refresh(); // Makes engine to refresh whole display content
71 <a name="reading-keys-with-nanoengine"></a>
72 ## Reading keys with NanoEngine
74 What, if we want to move yellow rectangle. There is easy way to do this with NanoEngine8. The engine supports up-to 6 keys: `BUTTON_DOWN`, `BUTTON_LEFT`, `BUTTON_RIGHT`, `BUTTON_UP`, `BUTTON_A`, `BUTTON_B`. All you need is to say the engine how it can get buttons state on your board. There are already 2 built-in implementations: `connectArduboyKeys()` allows using Arduboy platform hardware (remember that you need to replace ssd1306 oled with color ssd1331 oled), and `connectZKeypad()` allows using standard 5-keys Z-keypad (you can find it on E-bay). Or you can set custom key processing handler via `connectCustomKeys()` and implement your own hardware driver.
76 Example of using Z-keypad to move rectangle.
82 NanoRect rect = { {15,12}, {60,35} }; // Lets make rect smaller than in previous example
86 engine.canvas.clear();
87 engine.canvas.setColor(RGB_COLOR8(255,255,0));
88 engine.canvas.drawRect(rect); // draw rect in buffer
94 /* Init SPI 96x64 RBG oled. 3 - RESET, 4 - CS (can be omitted, oled CS must be pulled down), 5 - D/C */
95 ssd1331_96x64_spi_init(3, 4, 5);
98 engine.setFrameRate(30);
99 engine.drawCallback( drawAll ); // Set callback to draw parts, when NanoEngine8 asks
100 engine.connectZKeypad(0); // Connect ADC-buttons Z-keypad to analog A0 pin
101 engine.refresh(); // Makes engine to refresh whole display content at start-up
106 if (!engine.nextFrame()) return;
107 NanoPoint point = {0,0};
108 if (engine.pressed( BUTTON_RIGHT )) point.x = +1;
109 if (engine.pressed( BUTTON_LEFT )) point.x = -1;
110 if (engine.pressed( BUTTON_UP )) point.y = -1;
111 if (engine.pressed( BUTTON_DOWN )) point.y = +1;
112 engine.refresh(rect); // Update screen content at old rect position
113 rect += point; // Move rect according to pressed keys
114 engine.refresh(rect); // Update screen content at new rect position
115 engine.display(); // refresh display content
119 <a name="draw-monochrome-bitmap"></a>
120 ## Draw monochrome bitmap
127 const uint8_t heartSprite[8] PROGMEM =
141 engine.canvas.clear();
142 engine.canvas.setMode(0); // We want to draw non-transparent bitmap
143 engine.canvas.setColor(RGB_COLOR8(255,0,0)); // draw with red color
144 engine.canvas.drawBitmap1(10, 20, 8, 8, heartSprite);
150 /* Init SPI 96x64 RBG oled. 3 - RESET, 4 - CS (can be omitted, oled CS must be pulled down), 5 - D/C */
151 ssd1331_96x64_spi_init(3, 4, 5);
153 engine.drawCallback( drawAll ); // Set callback to draw parts, when NanoEngine8 asks
154 engine.refresh(); // Makes engine to refresh whole display content at start-up
159 if (!engine.nextFrame()) return;
160 engine.display(); // refresh display content
164 <a name="draw-moving-bitmap"></a>
165 ## Draw moving bitmap
167 In some applications like games, there is need to move bitmaps. It is easy to do this with ssd1306 library using NanoSprite objects. NanoSprite object is responsible for refreshing areas, touched by sprite. So, you need only to move sprite, where you want, the engine will take care of updating display content.
172 const uint8_t heartSprite[8] PROGMEM =
185 NanoSprite<NanoEngine8, engine> sprite( {0, 0}, {8, 8}, heartSprite );
189 engine.canvas.clear();
190 engine.canvas.setMode(0); // We want to draw non-transparent bitmap
191 engine.canvas.setColor(RGB_COLOR8(255,0,0)); // draw with red color
198 /* Init SPI 96x64 RBG oled. 3 - RESET, 4 - CS (can be omitted, oled CS must be pulled down), 5 - D/C */
199 ssd1331_96x64_spi_init(3, 4, 5);
201 engine.drawCallback( drawAll ); // Set callback to draw parts, when NanoEngine8 asks
202 engine.refresh(); // Makes engine to refresh whole display content at start-up
207 if (!engine.nextFrame()) return;
208 // You will see horizontal flying heart
209 sprite.moveBy( { 1, 0 } );
210 engine.display(); // refresh display content
214 <a name="what-if-not-to-use-draw-callbacks"></a>
215 ## What if not to use draw callbacks
217 If you don't want to use draw callbacks in your application, but still need a power of NanoEngine, then there is one way for you: to use full-screen double-buffering with NanoEngine. The example, you will find below, shows how to use full-screen double buffering for monochrome 128x64 ssd1306 oled display. This example can be run on Atmega328p and more powerful micro controllers. It clears back-buffer every time engine says to redraw the frame. But you can preserve previously prepared image by removing call to `engine.canvas.clear()`.
222 NanoEngine<BUFFER_128x64_MONO> engine;
226 // Init SPI 128x64 monochrome oled.
227 // 3 - RESET, 4 - CS (can be omitted, oled CS must be pulled down), 5 - D/C
228 ssd1306_128x64_spi_init(3, 4, 5);
231 engine.setFrameRate(30);
236 if (!engine.nextFrame()) return;
237 engine.canvas.clear(); // This step can be removed, if you don't want to clear buffer
238 engine.canvas.drawRect(15,12,70,55);
243 <a name="using-adafruit-gfx-with-nanoengine"></a>
244 ## Using Adafruit GFX with NanoEngine
246 Many developers are familiar with nice AdafruitGFX library. It provides rich set of graphics functions. Starting with 1.7.0 ssd1306 library it is possible to use AdafruiGFX api in combination with NanoEngine. And it is really easy.
247 You need to remember only, that AdafruitGFX uses different approach, when working with rectangles and monochrome images. NanoCanvas expects monochrome bitmaps in native ssd1306 format, while Adafruit uses more native format for human. If you compare an example below with examples above you will understand, what's the difference (heartImage). Refer to AdafruitGFX documentation.
250 // Define this before including library header, this will give Adafruit GFX support
251 // !!! Don't forget to install AdafruitGFX library to your Arduino IDE !!!
252 #define CONFIG_ADAFRUIT_GFX_ENABLE
256 // Now you can use AdafruitGFX by referencing engine.canvas
257 NanoEngine<ADATILE_8x8_RGB8> engine;
259 const PROGMEM uint8_t heartImage[8] =
273 engine.canvas.fillScreen( 0 );
274 engine.canvas.drawBitmap(10, 20, heartSprite, 8, 8, RGB_COLOR8(255,0,0)); // draw bitmap with red color
280 /* Init SPI 96x64 RBG oled. 3 - RESET, 4 - CS (can be omitted, oled CS must be pulled down), 5 - D/C */
281 ssd1331_96x64_spi_init(3, 4, 5);
283 engine.drawCallback( drawAll ); // Set callback to draw parts, when NanoEngine8 asks
284 engine.refresh(); // Makes engine to refresh whole display content at start-up
289 if (!engine.nextFrame()) return;
290 engine.display(); // refresh display content