102 lines
3.2 KiB
Python
102 lines
3.2 KiB
Python
import asyncio
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import smbus
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import time
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lock = asyncio.Lock()
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class LCD:
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def __init__(self, pi_rev = 2, i2c_addr = 0x3F, backlight = True):
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# device constants
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self.I2C_ADDR = i2c_addr
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self.LCD_WIDTH = 20 # Max. characters per line
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self.LCD_CHR = 1 # Mode - Sending data
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self.LCD_CMD = 0 # Mode - Sending command
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self.LCD_LINE_1 = 0x80 # LCD RAM addr for line one
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self.LCD_LINE_2 = 0xC0 # LCD RAM addr for line two
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self.LCD_LINE_3 = 0x94 # LCD RAM addr for line three
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self.LCD_LINE_4 = 0xD4 # LCD RAM addr for line four
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if backlight:
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# on
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self.LCD_BACKLIGHT = 0x08
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else:
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# off
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self.LCD_BACKLIGHT = 0x00
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self.ENABLE = 0b00000100 # Enable bit
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# Timing constants
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self.E_PULSE = 0.0005
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self.E_DELAY = 0.0005
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# Open I2C interface
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if pi_rev == 2:
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# Rev 2 Pi uses 1
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self.bus = smbus.SMBus(1)
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elif pi_rev == 1:
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# Rev 1 Pi uses 0
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self.bus = smbus.SMBus(0)
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else:
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raise ValueError('pi_rev param must be 1 or 2')
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# Initialise display
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self.lcd_byte(0x33, self.LCD_CMD) # 110011 Initialise
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self.lcd_byte(0x32, self.LCD_CMD) # 110010 Initialise
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self.lcd_byte(0x06, self.LCD_CMD) # 000110 Cursor move direction
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self.lcd_byte(0x0C, self.LCD_CMD) # 001100 Display On,Cursor Off, Blink Off
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self.lcd_byte(0x28, self.LCD_CMD) # 101000 Data length, number of lines, font size
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self.lcd_byte(0x01, self.LCD_CMD) # 000001 Clear display
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def lcd_byte(self, bits, mode):
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# Send byte to data pins
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# bits = data
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# mode = 1 for data, 0 for command
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bits_high = mode | (bits & 0xF0) | self.LCD_BACKLIGHT
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bits_low = mode | ((bits<<4) & 0xF0) | self.LCD_BACKLIGHT
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# High bits
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self.bus.write_byte(self.I2C_ADDR, bits_high)
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self.toggle_enable(bits_high)
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# Low bits
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self.bus.write_byte(self.I2C_ADDR, bits_low)
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self.toggle_enable(bits_low)
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def toggle_enable(self, bits):
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time.sleep(self.E_DELAY)
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self.bus.write_byte(self.I2C_ADDR, (bits | self.ENABLE))
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time.sleep(self.E_PULSE)
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self.bus.write_byte(self.I2C_ADDR,(bits & ~self.ENABLE))
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time.sleep(self.E_DELAY)
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async def async_message(self, string, line = 1):
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async with lock:
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result = await asyncio.to_thread(self._message, string = string, line = line)
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def _message(self, string, line = 1):
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# display message string on indicated LCD line
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if line == 1:
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lcd_line = self.LCD_LINE_1
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elif line == 2:
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lcd_line = self.LCD_LINE_2
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elif line == 3:
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lcd_line = self.LCD_LINE_3
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elif line == 4:
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lcd_line = self.LCD_LINE_4
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else:
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raise ValueError('line number out of range')
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string = string.ljust(self.LCD_WIDTH," ")
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self.lcd_byte(lcd_line, self.LCD_CMD)
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for i in range(self.LCD_WIDTH):
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self.lcd_byte(ord(string[i]), self.LCD_CHR)
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def clear(self):
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# clear LCD display
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self.lcd_byte(0x01, self.LCD_CMD)
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