max7219.py

# MicroPython max7219 8x8 LED matrix driver, cascadable, SPI interface

from micropython import const
import framebuf

_NOOP = const(0)
_DIGIT0 = const(1)
_DECODEMODE = const(9)
_INTENSITY = const(10)
_SCANLIMIT = const(11)
_SHUTDOWN = const(12)
_DISPLAYTEST = const(15)

class Max7219:
    def __init__(self, spi, cs, num):
        self.spi = spi
        self.cs = cs
        self.cs.init(cs.OUT, True)
        self.buffer = bytearray(8 * num)
        self.num = num
        fb = framebuf.FrameBuffer(self.buffer, 8 * num, 8, framebuf.MONO_HLSB)
        self.framebuf = fb
        # Provide methods for accessing FrameBuffer graphics primitives. This is a workround
        # because inheritance from a native class is currently unsupported.
        # http://docs.micropython.org/en/latest/pyboard/library/framebuf.html
        self.fill = fb.fill  # (col)
        self.pixel = fb.pixel # (x, y[, c])
        self.hline = fb.hline  # (x, y, w, col)
        self.vline = fb.vline  # (x, y, h, col)
        self.line = fb.line  # (x1, y1, x2, y2, col)
        self.rect = fb.rect  # (x, y, w, h, col)
        self.fill_rect = fb.fill_rect  # (x, y, w, h, col)
        self.text = fb.text  # (string, x, y, col=1)
        self.scroll = fb.scroll  # (dx, dy)
        self.blit = fb.blit  # (fbuf, x, y[, key])
        self.init()

    def _write(self, command, data):
        self.cs(0)
        for m in range(self.num):
            self.spi.write(bytearray([command, data]))
        self.cs(1)

    def init(self):
        for command, data in (
            (_SHUTDOWN, 0),
            (_DISPLAYTEST, 0),
            (_SCANLIMIT, 7),
            (_DECODEMODE, 0),
            (_SHUTDOWN, 1),
        ):
            self._write(command, data)

    def brightness(self, value):
        if not 0 <= value <= 15:
            raise ValueError("Brightness out of range")
        self._write(_INTENSITY, value)

    def show(self):
        for y in range(8):
            self.cs(0)
            for m in range(self.num):
                self.spi.write(bytearray([_DIGIT0 + y, self.buffer[(y * self.num) + m]]))
            self.cs(1)