87 lines
3.2 KiB
Python
87 lines
3.2 KiB
Python
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import utime
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import gc
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from lcd_api import LcdApi
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from machine import I2C
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# PCF8574 pin definitions
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MASK_RS = 0x01 # P0
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MASK_RW = 0x02 # P1
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MASK_E = 0x04 # P2
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SHIFT_BACKLIGHT = 3 # P3
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SHIFT_DATA = 4 # P4-P7
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class I2cLcd(LcdApi):
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#Implements a HD44780 character LCD connected via PCF8574 on I2C
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def __init__(self, i2c, i2c_addr, num_lines, num_columns):
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self.i2c = i2c
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self.i2c_addr = i2c_addr
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self.i2c.writeto(self.i2c_addr, bytes([0]))
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utime.sleep_ms(20) # Allow LCD time to powerup
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# Send reset 3 times
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self.hal_write_init_nibble(self.LCD_FUNCTION_RESET)
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utime.sleep_ms(5) # Need to delay at least 4.1 msec
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self.hal_write_init_nibble(self.LCD_FUNCTION_RESET)
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utime.sleep_ms(1)
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self.hal_write_init_nibble(self.LCD_FUNCTION_RESET)
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utime.sleep_ms(1)
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# Put LCD into 4-bit mode
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self.hal_write_init_nibble(self.LCD_FUNCTION)
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utime.sleep_ms(1)
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LcdApi.__init__(self, num_lines, num_columns)
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cmd = self.LCD_FUNCTION
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if num_lines > 1:
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cmd |= self.LCD_FUNCTION_2LINES
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self.hal_write_command(cmd)
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gc.collect()
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def hal_write_init_nibble(self, nibble):
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# Writes an initialization nibble to the LCD.
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# This particular function is only used during initialization.
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byte = ((nibble >> 4) & 0x0f) << SHIFT_DATA
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self.i2c.writeto(self.i2c_addr, bytes([byte | MASK_E]))
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self.i2c.writeto(self.i2c_addr, bytes([byte]))
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gc.collect()
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def hal_backlight_on(self):
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# Allows the hal layer to turn the backlight on
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self.i2c.writeto(self.i2c_addr, bytes([1 << SHIFT_BACKLIGHT]))
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gc.collect()
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def hal_backlight_off(self):
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#Allows the hal layer to turn the backlight off
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self.i2c.writeto(self.i2c_addr, bytes([0]))
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gc.collect()
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def hal_write_command(self, cmd):
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# Write a command to the LCD. Data is latched on the falling edge of E.
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byte = ((self.backlight << SHIFT_BACKLIGHT) |
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(((cmd >> 4) & 0x0f) << SHIFT_DATA))
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self.i2c.writeto(self.i2c_addr, bytes([byte | MASK_E]))
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self.i2c.writeto(self.i2c_addr, bytes([byte]))
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byte = ((self.backlight << SHIFT_BACKLIGHT) |
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((cmd & 0x0f) << SHIFT_DATA))
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self.i2c.writeto(self.i2c_addr, bytes([byte | MASK_E]))
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self.i2c.writeto(self.i2c_addr, bytes([byte]))
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if cmd <= 3:
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# The home and clear commands require a worst case delay of 4.1 msec
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utime.sleep_ms(5)
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gc.collect()
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def hal_write_data(self, data):
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# Write data to the LCD. Data is latched on the falling edge of E.
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byte = (MASK_RS |
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(self.backlight << SHIFT_BACKLIGHT) |
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(((data >> 4) & 0x0f) << SHIFT_DATA))
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self.i2c.writeto(self.i2c_addr, bytes([byte | MASK_E]))
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self.i2c.writeto(self.i2c_addr, bytes([byte]))
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byte = (MASK_RS |
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(self.backlight << SHIFT_BACKLIGHT) |
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((data & 0x0f) << SHIFT_DATA))
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self.i2c.writeto(self.i2c_addr, bytes([byte | MASK_E]))
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self.i2c.writeto(self.i2c_addr, bytes([byte]))
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gc.collect()
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