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488 lines
14 KiB
Go
488 lines
14 KiB
Go
// Copyright 2016 The Periph Authors. All rights reserved.
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// Use of this source code is governed under the Apache License, Version 2.0
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// that can be found in the LICENSE file.
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package ssd1306
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// Some have SPI enabled;
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// https://hallard.me/adafruit-oled-display-driver-for-pi/
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// https://learn.adafruit.com/ssd1306-oled-displays-with-raspberry-pi-and-beaglebone-black?view=all
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import (
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"bytes"
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"errors"
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"fmt"
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"image"
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"image/color"
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"image/draw"
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"periph.io/x/periph/conn"
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"periph.io/x/periph/conn/display"
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"periph.io/x/periph/conn/gpio"
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"periph.io/x/periph/conn/i2c"
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"periph.io/x/periph/conn/physic"
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"periph.io/x/periph/conn/spi"
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"periph.io/x/periph/devices/ssd1306/image1bit"
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)
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// FrameRate determines scrolling speed.
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type FrameRate byte
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// Possible frame rates. The value determines the number of refreshes between
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// movement. The lower value, the higher speed.
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const (
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FrameRate2 FrameRate = 7
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FrameRate3 FrameRate = 4
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FrameRate4 FrameRate = 5
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FrameRate5 FrameRate = 0
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FrameRate25 FrameRate = 6
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FrameRate64 FrameRate = 1
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FrameRate128 FrameRate = 2
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FrameRate256 FrameRate = 3
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)
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// Orientation is used for scrolling.
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type Orientation byte
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// Possible orientations for scrolling.
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const (
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Left Orientation = 0x27
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Right Orientation = 0x26
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UpRight Orientation = 0x29
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UpLeft Orientation = 0x2A
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)
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// DefaultOpts is the recommended default options.
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var DefaultOpts = Opts{
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W: 128,
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H: 64,
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Rotated: false,
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Sequential: false,
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SwapTopBottom: false,
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}
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// Opts defines the options for the device.
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type Opts struct {
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W int
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H int
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// Rotated determines if the display is rotated by 180°.
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Rotated bool
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// Sequential corresponds to the Sequential/Alternative COM pin configuration
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// in the OLED panel hardware. Try toggling this if half the rows appear to be
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// missing on your display.
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Sequential bool
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// SwapTopBottom corresponds to the Left/Right remap COM pin configuration in
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// the OLED panel hardware. Try toggling this if the top and bottom halves of
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// your display are swapped.
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SwapTopBottom bool
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}
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// NewSPI returns a Dev object that communicates over SPI to a SSD1306 display
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// controller.
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//
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// The SSD1306 can operate at up to 3.3Mhz, which is much higher than I²C. This
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// permits higher refresh rates.
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//
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// Wiring
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//
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// Connect SDA to SPI_MOSI, SCK to SPI_CLK, CS to SPI_CS.
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//
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// In 3-wire SPI mode, pass nil for 'dc'. In 4-wire SPI mode, pass a GPIO pin
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// to use.
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//
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// The RES (reset) pin can be used outside of this driver but is not supported
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// natively. In case of external reset via the RES pin, this device drive must
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// be reinstantiated.
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func NewSPI(p spi.Port, dc gpio.PinOut, opts *Opts) (*Dev, error) {
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if dc == gpio.INVALID {
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return nil, errors.New("ssd1306: use nil for dc to use 3-wire mode, do not use gpio.INVALID")
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}
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bits := 8
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if dc == nil {
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// 3-wire SPI uses 9 bits per word.
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bits = 9
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} else if err := dc.Out(gpio.Low); err != nil {
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return nil, err
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}
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c, err := p.Connect(3300*physic.KiloHertz, spi.Mode0, bits)
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if err != nil {
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return nil, err
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}
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return newDev(c, opts, true, dc)
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}
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// NewI2C returns a Dev object that communicates over I²C to a SSD1306 display
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// controller.
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func NewI2C(i i2c.Bus, opts *Opts) (*Dev, error) {
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// Maximum clock speed is 1/2.5µs = 400KHz.
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return newDev(&i2c.Dev{Bus: i, Addr: 0x3C}, opts, false, nil)
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}
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// Dev is an open handle to the display controller.
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type Dev struct {
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// Communication
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c conn.Conn
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dc gpio.PinOut
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spi bool
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// Display size controlled by the SSD1306.
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rect image.Rectangle
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// Mutable
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// See page 25 for the GDDRAM pages structure.
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// Narrow screen will waste the end of each page.
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// Short screen will ignore the lower pages.
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// There is 8 pages, each covering an horizontal band of 8 pixels high (1
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// byte) for 128 bytes.
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// 8*128 = 1024 bytes total for 128x64 display.
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buffer []byte
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// next is lazy initialized on first Draw(). Write() skips this buffer.
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next *image1bit.VerticalLSB
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startPage, endPage int
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startCol, endCol int
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scrolled bool
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halted bool
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}
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func (d *Dev) String() string {
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if d.spi {
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return fmt.Sprintf("ssd1360.Dev{%s, %s, %s}", d.c, d.dc, d.rect.Max)
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}
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return fmt.Sprintf("ssd1360.Dev{%s, %s}", d.c, d.rect.Max)
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}
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// ColorModel implements display.Drawer.
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//
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// It is a one bit color model, as implemented by image1bit.Bit.
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func (d *Dev) ColorModel() color.Model {
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return image1bit.BitModel
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}
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// Bounds implements display.Drawer. Min is guaranteed to be {0, 0}.
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func (d *Dev) Bounds() image.Rectangle {
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return d.rect
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}
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// Draw implements display.Drawer.
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//
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// It draws synchronously, once this function returns, the display is updated.
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// It means that on slow bus (I²C), it may be preferable to defer Draw() calls
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// to a background goroutine.
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func (d *Dev) Draw(r image.Rectangle, src image.Image, sp image.Point) error {
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var next []byte
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if img, ok := src.(*image1bit.VerticalLSB); ok && r == d.rect && img.Rect == d.rect && sp.X == 0 && sp.Y == 0 {
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// Exact size, full frame, image1bit encoding: fast path!
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next = img.Pix
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} else {
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// Double buffering.
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if d.next == nil {
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d.next = image1bit.NewVerticalLSB(d.rect)
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}
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next = d.next.Pix
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draw.Src.Draw(d.next, r, src, sp)
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}
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return d.drawInternal(next)
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}
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// Write writes a buffer of pixels to the display.
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//
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// The format is unsual as each byte represent 8 vertical pixels at a time. The
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// format is horizontal bands of 8 pixels high.
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//
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// This function accepts the content of image1bit.VerticalLSB.Pix.
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func (d *Dev) Write(pixels []byte) (int, error) {
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if len(pixels) != len(d.buffer) {
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return 0, fmt.Errorf("ssd1306: invalid pixel stream length; expected %d bytes, got %d bytes", len(d.buffer), len(pixels))
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}
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// Write() skips d.next so it saves 1kb of RAM.
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if err := d.drawInternal(pixels); err != nil {
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return 0, err
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}
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return len(pixels), nil
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}
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// Scroll scrolls an horizontal band.
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//
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// Only one scrolling operation can happen at a time.
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//
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// Both startLine and endLine must be multiples of 8.
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//
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// Use -1 for endLine to extend to the bottom of the display.
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func (d *Dev) Scroll(o Orientation, rate FrameRate, startLine, endLine int) error {
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h := d.rect.Dy()
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if endLine == -1 {
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endLine = h
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}
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if startLine >= endLine {
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return fmt.Errorf("startLine (%d) must be lower than endLine (%d)", startLine, endLine)
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}
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if startLine&7 != 0 || startLine < 0 || startLine >= h {
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return fmt.Errorf("invalid startLine %d", startLine)
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}
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if endLine&7 != 0 || endLine < 0 || endLine > h {
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return fmt.Errorf("invalid endLine %d", endLine)
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}
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startPage := uint8(startLine / 8)
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endPage := uint8(endLine / 8)
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d.scrolled = true
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if o == Left || o == Right {
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// page 28
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// <op>, dummy, <start page>, <rate>, <end page>, <dummy>, <dummy>, <ENABLE>
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return d.sendCommand([]byte{byte(o), 0x00, startPage, byte(rate), endPage - 1, 0x00, 0xFF, 0x2F})
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}
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// page 29
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// <op>, dummy, <start page>, <rate>, <end page>, <offset>, <ENABLE>
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// page 30: 0xA3 permits to set rows for scroll area.
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return d.sendCommand([]byte{byte(o), 0x00, startPage, byte(rate), endPage - 1, 0x01, 0x2F})
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}
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// StopScroll stops any scrolling previously set and resets the screen.
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func (d *Dev) StopScroll() error {
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return d.sendCommand([]byte{0x2E})
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}
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// SetContrast changes the screen contrast.
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//
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// Note: values other than 0xff do not seem useful...
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func (d *Dev) SetContrast(level byte) error {
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return d.sendCommand([]byte{0x81, level})
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}
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// Halt turns off the display.
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//
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// Sending any other command afterward reenables the display.
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func (d *Dev) Halt() error {
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d.halted = false
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err := d.sendCommand([]byte{0xAE})
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if err == nil {
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d.halted = true
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}
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return err
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}
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// Invert the display (black on white vs white on black).
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func (d *Dev) Invert(blackOnWhite bool) error {
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b := []byte{0xA6}
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if blackOnWhite {
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b[0] = 0xA7
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}
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return d.sendCommand(b)
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}
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//
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// newDev is the common initialization code that is independent of the
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// communication protocol (I²C or SPI) being used.
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func newDev(c conn.Conn, opts *Opts, usingSPI bool, dc gpio.PinOut) (*Dev, error) {
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if opts.W < 8 || opts.W > 128 || opts.W&7 != 0 {
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return nil, fmt.Errorf("ssd1306: invalid width %d", opts.W)
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}
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if opts.H < 8 || opts.H > 64 || opts.H&7 != 0 {
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return nil, fmt.Errorf("ssd1306: invalid height %d", opts.H)
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}
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nbPages := opts.H / 8
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pageSize := opts.W
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d := &Dev{
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c: c,
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spi: usingSPI,
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dc: dc,
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rect: image.Rect(0, 0, opts.W, opts.H),
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buffer: make([]byte, nbPages*pageSize),
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startPage: 0,
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endPage: nbPages,
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startCol: 0,
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endCol: opts.W,
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// Signal that the screen must be redrawn on first draw().
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scrolled: true,
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}
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if err := d.sendCommand(getInitCmd(opts)); err != nil {
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return nil, err
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}
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return d, nil
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}
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func getInitCmd(opts *Opts) []byte {
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// Set COM output scan direction; C0 means normal; C8 means reversed
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comScan := byte(0xC8)
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// See page 40.
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columnAddr := byte(0xA1)
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if opts.Rotated {
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// Change order both horizontally and vertically.
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comScan = 0xC0
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columnAddr = byte(0xA0)
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}
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// See page 40.
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hwLayout := byte(0x02)
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if !opts.Sequential {
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hwLayout |= 0x10
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}
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if opts.SwapTopBottom {
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hwLayout |= 0x20
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}
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// Set the max frequency. The problem with I²C is that it creates visible
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// tear down. On SPI at high speed this is not visible. Page 23 pictures how
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// to avoid tear down. For now default to max frequency.
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freq := byte(0xF0)
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// Initialize the device by fully resetting all values.
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// Page 64 has the full recommended flow.
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// Page 28 lists all the commands.
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return []byte{
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0xAE, // Display off
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0xD3, 0x00, // Set display offset; 0
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0x40, // Start display start line; 0
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columnAddr, // Set segment remap; RESET is column 127.
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comScan, //
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0xDA, hwLayout, // Set COM pins hardware configuration; see page 40
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0x81, 0xFF, // Set max contrast
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0xA4, // Set display to use GDDRAM content
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0xA6, // Set normal display (0xA7 for inverted 0=lit, 1=dark)
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0xD5, freq, // Set osc frequency and divide ratio; power on reset value is 0x80.
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0x8D, 0x14, // Enable charge pump regulator; page 62
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0xD9, 0xF1, // Set pre-charge period; from adafruit driver
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0xDB, 0x40, // Set Vcomh deselect level; page 32
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0x2E, // Deactivate scroll
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0xA8, byte(opts.H - 1), // Set multiplex ratio (number of lines to display)
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0x20, 0x00, // Set memory addressing mode to horizontal
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0x21, 0, uint8(opts.W - 1), // Set column address (Width)
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0x22, 0, uint8(opts.H/8 - 1), // Set page address (Pages)
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0xAF, // Display on
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}
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}
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func (d *Dev) calculateSubset(next []byte) (int, int, int, int, bool) {
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w := d.rect.Dx()
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h := d.rect.Dy()
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startPage := 0
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endPage := h / 8
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startCol := 0
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endCol := w
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if d.scrolled {
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// Painting disable scrolling but if scrolling was enabled, this requires a
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// full screen redraw.
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d.scrolled = false
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} else {
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// Calculate the smallest square that need to be sent.
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pageSize := w
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// Top.
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for ; startPage < endPage; startPage++ {
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x := pageSize * startPage
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y := pageSize * (startPage + 1)
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if !bytes.Equal(d.buffer[x:y], next[x:y]) {
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break
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}
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}
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// Bottom.
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for ; endPage > startPage; endPage-- {
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x := pageSize * (endPage - 1)
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y := pageSize * endPage
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if !bytes.Equal(d.buffer[x:y], next[x:y]) {
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break
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}
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}
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if startPage == endPage {
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// Early exit, the image is exactly the same.
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return 0, 0, 0, 0, true
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}
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// TODO(maruel): This currently corrupts the screen. Likely a small error
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// in the way the commands are sent.
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/*
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// Left.
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for ; startCol < endCol; startCol++ {
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for i := startPage; i < endPage; i++ {
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x := i*pageSize + startCol
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if d.buffer[x] != next[x] {
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goto breakLeft
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}
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}
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}
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breakLeft:
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// Right.
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for ; endCol > startCol; endCol-- {
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for i := startPage; i < endPage; i++ {
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x := i*pageSize + endCol - 1
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if d.buffer[x] != next[x] {
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goto breakRight
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}
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}
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}
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breakRight:
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*/
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}
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return startPage, endPage, startCol, endCol, false
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}
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// drawInternal sends image data to the controller.
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func (d *Dev) drawInternal(next []byte) error {
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startPage, endPage, startCol, endCol, skip := d.calculateSubset(next)
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if skip {
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return nil
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}
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copy(d.buffer, next)
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if d.startPage != startPage || d.endPage != endPage || d.startCol != startCol || d.endCol != endCol {
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d.startPage = startPage
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d.endPage = endPage
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d.startCol = startCol
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d.endCol = endCol
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cmd := []byte{
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0x21, uint8(d.startCol), uint8(d.endCol - 1), // Set column address (Width)
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0x22, uint8(d.startPage), uint8(d.endPage - 1), // Set page address (Pages)
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}
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if err := d.sendCommand(cmd); err != nil {
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return err
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}
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}
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// Write the subset of the data as needed.
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pageSize := d.rect.Dx()
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return d.sendData(d.buffer[startPage*pageSize+startCol : (endPage-1)*pageSize+endCol])
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}
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func (d *Dev) sendData(c []byte) error {
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if d.halted {
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// Transparently enable the display.
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if err := d.sendCommand(nil); err != nil {
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return err
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}
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}
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if d.spi {
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// 4-wire SPI.
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if err := d.dc.Out(gpio.High); err != nil {
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return err
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}
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return d.c.Tx(c, nil)
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}
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return d.c.Tx(append([]byte{i2cData}, c...), nil)
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}
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func (d *Dev) sendCommand(c []byte) error {
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if d.halted {
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// Transparently enable the display.
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c = append([]byte{0xAF}, c...)
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d.halted = false
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}
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if d.spi {
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if d.dc == nil {
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// 3-wire SPI.
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return errors.New("ssd1306: 3-wire SPI mode is not yet implemented")
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}
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// 4-wire SPI.
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if err := d.dc.Out(gpio.Low); err != nil {
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return err
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}
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return d.c.Tx(c, nil)
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}
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return d.c.Tx(append([]byte{i2cCmd}, c...), nil)
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}
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const (
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i2cCmd = 0x00 // I²C transaction has stream of command bytes
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i2cData = 0x40 // I²C transaction has stream of data bytes
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)
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var _ display.Drawer = &Dev{}
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