Embedded Files
原理介紹
七段顯示器是發光元件，其基本單元是發光二極體，根據段數，顯示器分為七段管和八段管。八段管比七段管還多一個發光二極體單元(小數點多一個)。發光二極體單元可根據連接方式分為共陽極和共陰極二極體。共陽極二極體是指發光連接到+5V的所有陽極。當任何一段發光二極體的陰極為低電位十，相應的段將點亮; 當陰極處於高電位時，該段保持不亮。共陰極二極體是指發光連接到GND的所有陰極。當任何一段發光二極體的陽極為高電位時，相應的段將亮起，當陽極為低電位時，該段也保持不亮。當我們想要顯示多個數位時，則需要多位元7段顯示器。這裡我們介紹4個7段顯示器。
電路圖
程式列表
Python - max7219_8digit.py
# Reference:
# Micropython driver for the max7219 with 8 x 7segment display
# https://github.com/pdwerryhouse/max7219_8digit
CHAR_MAP = {
' ': 0x00, '0': 0x7e, '1': 0x30, '2': 0x6d,
'3': 0x79, '4': 0x33, '5': 0x5b, '6': 0x5f,
'7': 0x70, '8': 0x7f, '9': 0x7b, 'a': 0x77,
'b': 0x1f, 'c': 0x4e, 'd': 0x3d, 'e': 0x4f,
'f': 0x47, 'g': 0x7b, 'h': 0x37, 'i': 0x30,
'j': 0x3c, 'k': 0x57, 'l': 0x0e, 'm': 0x54,
'n': 0x15, 'o': 0x1d, 'p': 0x67, 'q': 0x73,
'r': 0x05, 's': 0x5b, 't': 0x0f, 'u': 0x1c,
'v': 0x3e, 'w': 0x2a, 'x': 0x37, 'y': 0x3b,
'z': 0x6d, 'A': 0x77, 'B': 0x1f, 'C': 0x4e,
'D': 0x3d, 'E': 0x4f, 'F': 0x47, 'G': 0x7b,
'H': 0x37, 'I': 0x30, 'J': 0x3c, 'K': 0x57,
'L': 0x0e, 'M': 0x54, 'N': 0x15, 'O': 0x1d,
'P': 0x67, 'Q': 0x73, 'R': 0x05, 'S': 0x5b,
'T': 0x0f, 'U': 0x1c, 'V': 0x3e, 'W': 0x2a,
'X': 0x37, 'Y': 0x3b, 'Z': 0x6d, ' ': 0x00,
'-': 0x01, '\xb0': 0x63, '.': 0x80
}
REG_NO_OP = 0x00
REG_DIGIT_BASE = 0x01
REG_DIGIT0 = 0x01
REG_DIGIT1 = 0x02
REG_DIGIT2 = 0x03
REG_DIGIT3 = 0x04
REG_DIGIT4 = 0x05
REG_DIGIT5 = 0x06
REG_DIGIT6 = 0x07
REG_DIGIT7 = 0x08
REG_DECODE_MODE = 0x09 #Decode-Mode Register
# 0x00: No decode for digits 7¡V0
# 0x01: Code B decode for digit 0,No decode for digits 7¡V1
# 0x0F: Code B decode for digits 3¡V0, No decode for digits 7¡V4
# 0xFF: Code B decode for digits 7¡V0,
REG_INTENSITY = 0x0A #Intensity Register Format
# MAX7219 MAX7221
# 0x00: 1/16 1/32
# 0x01: 3/32 2/16
# 0x02: 5/32 3/16
# 0x03: 7/32 4/16
# 0x04: 9/32 5/16
# 0x05: 11/32 6/16
# 0x06: 13/32 7/16
# 0x07: 15/32 8/16
# 0x08: 17/32 9/16
# 0x09: 19/32 10/16
# 0x0A: 21/32 11/16
# 0x0B: 23/32 12/16
# 0x0C: 25/32 13/16
# 0x0D: 27/32 14/16
# 0x0E: 29/32 15/16
# 0x0F: 15/16 31/32
REG_SCAN_LIMIT = 0x0B #Scan-Limit Register Format
# 0x00: Display digits 0 X X X X X X X
# 0x01: Display digits 0 1 X X X X X X
# 0x02: Display digits 0 1 2 X X X X X
# 0x03: Display digits 0 1 2 3 X X X X
# 0x04: Display digits 0 1 2 3 4 X X X
# 0x05: Display digits 0 1 2 3 4 5 X X
# 0x06: Display digits 0 1 2 3 4 5 6 X
# 0x07: Display digits 0 1 2 3 4 5 6 7
REG_SHUTDOWN = 0x0C #Shutdown Register Format
# 0x00 Shutdown Mode
# 0x01 Normal Operation
REG_DISPLAY_TEST = 0x0F #Display-Test Register Format
# 0x00 Normal Operation
# 0x01 Display Test Mode
NUM_DIGITS = 8
class Display7seg:
def __init__(self, spi, intensity=7):
self.spi = spi
self.buffer = bytearray(NUM_DIGITS)
self.intensity = intensity
self.init()
def init(self):
for command, data in (
(REG_SHUTDOWN, 0),
(REG_DECODE_MODE, 0),
(REG_INTENSITY, self.intensity),
(REG_SCAN_LIMIT, 7),
(REG_DISPLAY_TEST, 0),
(REG_SHUTDOWN, 1),
):
self.set_register(command, data)
def set_register(self, register, value):
self.spi.write(bytearray([value, register]))
def write_to_buffer(self, s):
l = len(s)
if l < NUM_DIGITS:
s = "%-8s" % s
for i in range(0,NUM_DIGITS):
self.buffer[7-i] = self.decode_char(s[i])
def decode_char(self, c):
d = CHAR_MAP.get(c)
return d if d != None else ' '
def write_number(self, value, zeroPad=False, leftJustify=False):
# Take number, format it, look up characters then pass to buffer.
if len(str(value)) > NUM_DIGITS:
raise OverflowError('{0} too large for display'.format(value))
size = NUM_DIGITS
formatStr = '%'
if zeroPad:
formatStr += '0'
if leftJustify:
size *= -1
formatStr = '{fmt}{size}i'.format(fmt=formatStr, size=size)
position = REG_DIGIT7
strValue = formatStr % value
# look up each digit's character
# then send to buffer
for char in strValue:
self.buffer[position - 1] = self.letter(char)
position -= 1
def letter(self, char):
# Look up character on digits table & return
value = CHAR_MAP.get(str(char))
return value
def intensity(self, value):
self.send(self.intensity, value)
def brightness(self, value):
if not 0 <= value <= 15:
raise ValueError("Brightness out of range")
self.set_register(REG_INTENSITY, value)
def show(self):
for y in range(0,NUM_DIGITS):
self.set_register(REG_DIGIT_BASE + y, self.buffer[y])
Python - max7219_8digit_Test.py
from machine import SPI, Switch
import max7219_8digit
import utime
# Connections:
# EPY SPI0 MAX7219
# 3V3 VCC
# GND GND
# MOSI P6 -> DIN
# CS P9 -> CS
# CLK P8 -> CLK
# MISO P7
spi0 = None
spi0=SPI(0, SPI.MASTER, baudrate=5000000,polarity=1, phase=0, bits=16) #For Hardware SPI bus
# baudrate is the SCK clock rate.
# polarity can be 0 or 1, and is the level the idle clock line sits at.
# phase can be 0 or 1 to sample data on the first or second clock edge respectively.
# bits is the width in bits of each transfer. Only 8 is guaranteed to be supported by all hardware.
# firstbit can be SPI.MSB or SPI.LSB.
# Start Function
if __name__ == '__main__':
KeyA = Switch('keya')
display = max7219_8digit.Display7seg(spi0)
display.write_to_buffer('EPYTHON')
display.show()
utime.sleep_ms(1000)
for NUM in range(0,50000):
display.write_number(NUM)
display.show()
if (KeyA.value()) == True: #¦pªG«öÁäC³Q«ö¤U
break
utime.sleep_ms(100)
spi0 .deinit()
執行結果
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