OneBitDisplay (1-bpp OLED/LCD library)

Project started 3/23/2020
Copyright (c) 2020 BitBank Software, Inc.
Written by Larry Bank
bitbank@pobox.com


The purpose of this code is to easily control monochrome (1-bit per pixel) OLED and LCD displays. The displays can be connected to the traditional I2C or SPI bus, or you can use GPIO pins to bit bang the signals.

On AVR microcontrollers, there is an optimized option to speed up access to the GPIO pins to allow speeds which match or exceed normal I2C speeds. The pins are numbered with the Port letter as the first digit followed by the bit number. For example, To use bit 0 of Port B, you would reference pin number 0xb0.

Includes the unique feature that the I2C init function can optionally detect the display address (0x3C or 0x3D) and the controller type (SSD1306, SH1106 or SH1107).

I try to support as many OLEDs as I can. I was able to justify buying a bunch of different sized SSD1306 displays because they're around $2 each. A generous patron donated money so that I could purchase Pimoroni's 128x128 OLED and add support for it. It uses the SH1107 controller and behaves very similarly to the SH1106.

Features:
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• C API and C++ wrapper class which mimics the Adafruit_GFX API
• Supports any number of simultaneous displays of any type (mix and match)
  
• Optionally detect the display address and type (I2C only)
  
• Supports 72x40, 96x16, 64x32, 128x32, 128x64, 64x128 (SH1107), 128x128 (SH1107) and 132x64 (SH1106) OLED display sizes
  
• Supports 96x68 HX1230, 84x48 Nokia 5110 and 128x64 ST7567/UC1701 mono LCDs
  
• Supports 144x168 and 400x240 Sharp Memory LCDs
  
• Supports the ST7302 low power LCD (250x122, 2.13")
• NEW supports a few popular epd (e-ink) panels
• Virtual displays of any size which can be drawn across multiple physical displays
• Flexible copy function can convert the internal pixel format to any output format and orientation
• Drive displays from I2C, SPI or any GPIO pins (virtual I2C/SPI)
  
• Includes 5 sizes of fixed fonts (6x8, 8x8, 12x16, 16x16, 16x32)
  
• Text drawing at any fractional scale (e.g. 1.25x), and any of 4 directions/rotations
  
• Can use Adafruit_GFX format bitmap fonts (proportional and fixed)
  
• Deferred rendering allows preparing a back buffer, then displaying it (usually faster)
  
• Text scrolling features (vertical and horizontal)
  
• Text cursor position with optional line wrap
  
• A function to load a Windows BMP file
  
• Pixel drawing on SH1106/7 without needing backing RAM
  
• Optimized Bresenham line drawing
  
• Optimized Bresenham outline and filled ellipse drawing
  
• Optimized outline and filled rectangle drawing
  
• Optional backing RAM (needed for some text and drawing functions)
  
• 16x16 Tile/Sprite drawing at any angle.
  
• Run full frame animations at high frame rates with a simple API
  
  This code depends on the BitBang_I2C library. You can download it here:
  https://github.com/bitbank2/BitBang_I2C
  See the Wiki for help getting started
  https://github.com/bitbank2/OneBitDisplay/wiki
  
  

A few words about fonts
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The library includes 3 fixed fonts (6x8, 8x8 and 16x32). The 16x32 font is disabled when compiling for AVR targets (e.g. Arduino Uno) to save FLASH program space. The other 2 fonts offer 2x stretched versions (12x16 from 6x8 and 16x16 from 8x8). A simple smoothing algorithm is applied to the stretched 6x8 font to make it look better. In the photo above are the first 4 font sizes shown on a 128x64 yellow OLED display. Only 96 ASCII characters are defined per font to save space. To use more elaborate fonts with more extensive character support, use Adafruit_GFX format bitmap fonts with the obdWriteStringCustom() function.

Sharp Memory LCD Support
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New - support for the Sharp 144x168 and 400x240 memory LCDs. These are a different type of LCD that have a high refresh rate and low power usage. They cost quite a bit more than normal LCDs. They require a memory back buffer to use the drawing functions due to the way data is written to them one line at a time. I've also added a specific function if you would like to skip the back buffer - obdWriteLCDLine(). It allows you to write a single line of pixels without needing any additional memory. Please see the Wiki for more details.

Instructions for use:
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Start by initializing the library. Either using hardware I2C, bit-banged I2C or SPI to talk to the display. For I2C, the address of the display will be detected automatically (either 0x3c or 0x3d) or you can specify it. The typical MCU only allows setting the I2C speed up to 400Khz, but the SSD1306 displays can handle a much faster signal. With the bit-bang code, you can usually specify a stable 800Khz clock and with Cortex-M0 targets, the hardware I2C can be told to be almost any speed, but the displays I've tested tend to stop working beyond 1.6Mhz.

After initializing the display you can begin drawing text or graphics on it. The final parameter of all of the drawing functions is a render flag. When true, the graphics will be sent to the internal backing buffer (when available) and sent to the display. You optionally pass the library a backing buffer (if your MCU has enough RAM) with the obdSetBackBuffer() function. When the render flag is false, the graphics will only be drawn into the internal buffer. Once you're ready to send the pixels to the display, call obdDumpBuffer(NULL) and it will copy the internal buffer in its entirety to the display.

The text drawing function now has a scroll offset parameter. This tells it how many pixels of the text to skip before drawing the text at the given destination coordinates. For example, if you pass a value of 20 for the scroll offset and are using an 8-pixel wide font (FONT_8x8), the first two and a half characters will not be drawn; the second half of the third and subsequent characters will be drawn starting at the x/y you specified. This allows you to create a scrolling text effect by repeatedly calling the oledWriteString() function with progressively larger scroll offset values to make the text scroll from right to left.

If you find this code useful, please consider sending a donation or becomming a Github sponsor.