MaxO/max7219.py

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2020-11-15 17:47:23 +00:00
from machine import Pin
from micropython import const
import framebuf
_DIGIT_0 = const(0x1)
_DECODE_MODE = const(0x9)
_NO_DECODE = const(0x0)
_INTENSITY = const(0xa)
_INTENSITY_MIN = const(0x0)
_SCAN_LIMIT = const(0xb)
_DISPLAY_ALL_DIGITS = const(0x7)
_SHUTDOWN = const(0xc)
_SHUTDOWN_MODE = const(0x0)
_NORMAL_OPERATION = const(0x1)
_DISPLAY_TEST = const(0xf)
_DISPLAY_TEST_NORMAL_OPERATION = const(0x0)
_MATRIX_SIZE = const(8)
class Max7219(framebuf.FrameBuffer):
"""
Driver for MAX7219 8x8 LED matrices
Example for ESP8266 with 2x4 matrices (one on top, one on bottom),
so we have a 32x16 display area:
>>> from machine import Pin, SPI
>>> from max7219 import Max7219
>>> spi = SPI(1, baudrate=10000000)
>>> screen = Max7219(32, 16, spi, Pin(15))
>>> screen.rect(0, 0, 32, 16, 1) # Draws a frame
>>> screen.text('Hi!', 4, 4, 1)
>>> screen.show()
On some matrices, the display is inverted (rotated 180°), in this case
you can use `rotate_180=True` in the class constructor.
"""
def __init__(self, width, height, spi, cs, rotate_180=False):
# Pins setup
self.spi = spi
self.cs = cs
self.cs.init(Pin.OUT, True)
# Dimensions
self.width = width
self.height = height
# Guess matrices disposition
self.cols = width // _MATRIX_SIZE
self.rows = height // _MATRIX_SIZE
self.nb_matrices = self.cols * self.rows
self.rotate_180 = rotate_180
# 1 bit per pixel (on / off) -> 8 bytes per matrix
self.buffer = bytearray(width * height // 8)
format = framebuf.MONO_HLSB if not self.rotate_180 else framebuf.MONO_HMSB
super().__init__(self.buffer, width, height, format)
# Init display
self.init_display()
def _write_command(self, command, data):
"""Write command on SPI"""
cmd = bytearray([command, data])
self.cs(0)
for matrix in range(self.nb_matrices):
self.spi.write(cmd)
self.cs(1)
def init_display(self):
"""Init hardware"""
for command, data in (
(_SHUTDOWN, _SHUTDOWN_MODE), # Prevent flash during init
(_DECODE_MODE, _NO_DECODE),
(_DISPLAY_TEST, _DISPLAY_TEST_NORMAL_OPERATION),
(_INTENSITY, _INTENSITY_MIN),
(_SCAN_LIMIT, _DISPLAY_ALL_DIGITS),
(_SHUTDOWN, _NORMAL_OPERATION), # Let's go
):
self._write_command(command, data)
self.fill(0)
self.show()
def brightness(self, value):
"""Set display brightness (0 to 15)"""
if not 0 <= value < 16:
raise ValueError('Brightness must be between 0 and 15')
self._write_command(_INTENSITY, value)
def show(self):
"""Update display"""
# Write line per line on the matrices
for line in range(8):
self.cs(0)
for matrix in range(self.nb_matrices):
# Guess where the matrix is placed
row, col = divmod(matrix, self.cols)
# Compute where the data starts
if not self.rotate_180:
offset = row * 8 * self.cols
index = col + line * self.cols + offset
else:
offset = 8 * self.cols - row * self.cols * 8 - 1
index = self.cols * (8 - line) - col + offset
self.spi.write(bytearray([_DIGIT_0 + line, self.buffer[index]]))
self.cs(1)