ssd1306.py

# The MIT License (MIT)
#
# Copyright (c) 2014 Kenneth Henderick
#
# Permission is hereby granted, free of charge, to any person obtaining a copy
# of this software and associated documentation files (the "Software"), to deal
# in the Software without restriction, including without limitation the rights
# to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
# copies of the Software, and to permit persons to whom the Software is
# furnished to do so, subject to the following conditions:
#
# The above copyright notice and this permission notice shall be included in
# all copies or substantial portions of the Software.
#
# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
# AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
# LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
# OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
# THE SOFTWARE.

import pyb
from font import strtobit, reverse
 

# Constants
DISPLAYOFF          = 0xAE
SETCONTRAST         = 0x81
DISPLAYALLON_RESUME = 0xA4
DISPLAYALLON        = 0xA5
NORMALDISPLAY       = 0xA6
INVERTDISPLAY       = 0xA7
DISPLAYON           = 0xAF
SETDISPLAYOFFSET    = 0xD3
SETCOMPINS          = 0xDA
SETVCOMDETECT       = 0xDB
SETDISPLAYCLOCKDIV  = 0xD5
SETPRECHARGE        = 0xD9
SETMULTIPLEX        = 0xA8
SETLOWCOLUMN        = 0x00
SETHIGHCOLUMN       = 0x10
SETSTARTLINE        = 0x40
MEMORYMODE          = 0x20
COLUMNADDR          = 0x21
PAGEADDR            = 0x22
COMSCANINC          = 0xC0
COMSCANDEC          = 0xC8
SEGREMAP            = 0xA0
CHARGEPUMP          = 0x8D
EXTERNALVCC         = 0x10
SWITCHCAPVCC        = 0x20
SETPAGEADDR         = 0xB0
SETCOLADDR_LOW      = 0x00
SETCOLADDR_HIGH     = 0x10
ACTIVATE_SCROLL                      = 0x2F
DEACTIVATE_SCROLL                    = 0x2E
SET_VERTICAL_SCROLL_AREA             = 0xA3
RIGHT_HORIZONTAL_SCROLL              = 0x26
LEFT_HORIZONTAL_SCROLL               = 0x27
VERTICAL_AND_RIGHT_HORIZONTAL_SCROLL = 0x29
VERTICAL_AND_LEFT_HORIZONTAL_SCROLL  = 0x2A

# I2C devices are accessed through a Device ID. This is a 7-bit
# value but is sometimes expressed left-shifted by 1 as an 8-bit value.
# A pin on SSD1306 allows it to respond to ID 0x3C or 0x3D. The board
# I bought from ebay used a 0-ohm resistor to select between "0x78"
# (0x3c << 1) or "0x7a" (0x3d << 1). The default was set to "0x78"
DEVID = 0x3c

# I2C communication here is either <DEVID> <CTL_CMD> <command byte>
# or <DEVID> <CTL_DAT> <display buffer bytes> <> <> <> <>...
# These two values encode the Co (Continuation) bit as b7 and the
# D/C# (Data/Command Selection) bit as b6.
CTL_CMD = 0x80
CTL_DAT = 0x40

class SSD1306(object):

  def __init__(self, pinout, height=32, external_vcc=True, i2c_devid=DEVID):
    self.external_vcc = external_vcc
    self.height       = 32 if height == 32 else 64
    self.pages        = int(self.height / 8)
    self.columns      = 128

    # Infer interface type from entries in pinout{}
    if 'dc' in pinout:
      # SPI
      rate = 16 * 1024 * 1024
      self.spi = pyb.SPI(2, pyb.SPI.MASTER, baudrate=rate, polarity=1, phase=0)  # SCK: Y6: MOSI: Y8
      self.dc  = pyb.Pin(pinout['dc'],  pyb.Pin.OUT_PP, pyb.Pin.PULL_DOWN)
      self.res = pyb.Pin(pinout['res'], pyb.Pin.OUT_PP, pyb.Pin.PULL_DOWN)
      self.offset = 0
    else:
      # Infer bus number from pin
      if pinout['sda'] == 'X10':
        self.i2c = pyb.I2C(1)
      else:
        self.i2c = pyb.I2C(2)
      self.i2c.init(pyb.I2C.MASTER, baudrate=400000) # 400kHz
      self.devid = i2c_devid
      # used to reserve an extra byte in the image buffer AND as a way to
      # infer the interface type
      self.offset = 1
      # I2C command buffer
      self.cbuffer = bytearray(2)
      self.cbuffer[0] = CTL_CMD
    self.buffer = bytearray(self.offset + self.pages * self.columns)

  def clear(self):
 # avoid using storage allocator
    for i in range(len(self.buffer)):
      self.buffer[i]=0
    if self.offset == 1:
      self.buffer[0] = CTL_DAT

  def write_command(self, command_byte):
    if self.offset == 1:
      self.cbuffer[1] = command_byte
      self.i2c.send(self.cbuffer, addr=self.devid, timeout=5000)
    else:
      self.dc.low()
      self.spi.send(command_byte)

  def invert_display(self, invert):
    self.write_command(INVERTDISPLAY if invert else NORMALDISPLAY)

  def display(self):
    self.write_command(COLUMNADDR)
    self.write_command(0)
    self.write_command(self.columns - 1)
    self.write_command(PAGEADDR)
    self.write_command(0)
    self.write_command(self.pages - 1)
    if self.offset == 1:
      self.i2c.send(self.buffer, addr=self.devid, timeout=5000)
    else:
      self.dc.high()
      self.spi.send(self.buffer)

  def pixel(self, x, y, state):
    if (x<0) or (y<0):
      return
    x = 127 - x
    y = 63 - y
    if (x<0) or (y<0):
      return
    index = x + (int(y / 8) * self.columns)
    if state:
      self.buffer[self.offset + index] |= (1 << (y & 7))
    else:
      self.buffer[self.offset + index] &= ~(1 << (y & 7))

  def set_bytes(self, x, y, bs):
        x = 127 - x
        y = 63 - y
        index = x + (int(y / 8) * self.columns)
        for i in range(len(bs)):
          self.buffer[self.offset + index-i] = bs[i]

  def text(self, s, x, y, state = True):
    self.set_bytes(x,y,strtobit(s))
          
  def init_display(self):
    chargepump = 0x10 if self.external_vcc else 0x14
    precharge  = 0x22 if self.external_vcc else 0xf1
    multiplex  = 0x1f if self.height == 32 else 0x3f
    compins    = 0x02 if self.height == 32 else 0x12
    contrast   = 0xff # 0x8f if self.height == 32 else (0x9f if self.external_vcc else 0x9f)
    data = [DISPLAYOFF,
            SETDISPLAYCLOCKDIV, 0x80,
            SETMULTIPLEX, multiplex,
            SETDISPLAYOFFSET, 0x00,
            SETSTARTLINE | 0x00,
            CHARGEPUMP, chargepump,
            MEMORYMODE, 0x00,
            SEGREMAP | 0x10,
            COMSCANDEC,
            SETCOMPINS, compins,
            SETCONTRAST, contrast,
            SETPRECHARGE, precharge,
            SETVCOMDETECT, 0x40,
            DISPLAYALLON_RESUME,
            NORMALDISPLAY,
            DISPLAYON]
    for item in data:
      self.write_command(item)
    self.clear()
    self.display()

  def poweron(self):
    if self.offset == 1:
      pyb.delay(10)
    else:
      self.res.high()
      pyb.delay(1)
      self.res.low()
      pyb.delay(10)
      self.res.high()
      pyb.delay(10)

  def poweroff(self):
    self.write_command(DISPLAYOFF)

  def contrast(self, contrast):
    self.write_command(SETCONTRAST)
    self.write_command(contrast)