002 - Raspberry Pi Pico: LCD 4-bit Mode

 1# More details can be found in TechToTinker.blogspot.com 
 2# George Bantique | tech.to.tinker@gmail.com
 3
 4from machine import Pin
 5from gpio_lcd import GpioLcd
 6
 7# Create the LCD object
 8lcd = GpioLcd(rs_pin=Pin(8),
 9              enable_pin=Pin(9),
10              d4_pin=Pin(10),
11              d5_pin=Pin(11),
12              d6_pin=Pin(12),
13              d7_pin=Pin(13),
14              num_lines=2, num_columns=16)
15
16
17
18# #The following line of codes should be tested using the REPL
19#
20# #1. To print a string to the lcd, you can use
21lcd.putstr('Hello world!')
22# #2. Now, to clear the display.
23# lcd.clear()
24# #3. and to exactly position the cursor location
25# lcd.move_to(1,1)
26# lcd.putstr('TechToTinker')
27# # If you do not set the cursor position,
28# # the character will be displayed in the
29# # default cursor position starting from
30# # 0, x and 0, y location which is the top left-hand side.
31# # There are other useful functions we can use in using the lcd.
32# #4. Show the cursor
33# lcd.show_cursor()
34# #5. Hide the cursor
35# lcd.hide_cursor()
36# #6. Turn ON blinking cursor
37# lcd.blink_cursor_on()
38# #7. Turn OFF blinking cursor
39# lcd.blink_cursor_off()
40# #8. Disable display
41# lcd.display_off()
42# this will only hide the characters
43# #9. Enable display
44# lcd.display_on()
45# #10. Turn backlight OFF
46# lcd.backlight_off()
47# #11. Turn backlight ON
48# lcd.backlight_on()
49# # 12. Print a single character
50# lcd.putchar('x')
51# but this will only print 1 character
52# #13. Display a custom characters
53# happy_face = bytearray([0x00,0x0A,0x00,0x04,0x00,0x11,0x0E,0x00])
54# lcd.custom_char(0, happy_face)
55# lcd.putchar(chr(0))

  1"""Provides an API for talking to HD44780 compatible character LCDs."""
  2
  3import time
  4
  5class LcdApi:
  6    """Implements the API for talking with HD44780 compatible character LCDs.
  7    This class only knows what commands to send to the LCD, and not how to get
  8    them to the LCD.
  9    It is expected that a derived class will implement the hal_xxx functions.
 10    """
 11
 12    # The following constant names were lifted from the avrlib lcd.h
 13    # header file, however, I changed the definitions from bit numbers
 14    # to bit masks.
 15    #
 16    # HD44780 LCD controller command set
 17
 18    LCD_CLR = 0x01              # DB0: clear display
 19    LCD_HOME = 0x02             # DB1: return to home position
 20
 21    LCD_ENTRY_MODE = 0x04       # DB2: set entry mode
 22    LCD_ENTRY_INC = 0x02        # --DB1: increment
 23    LCD_ENTRY_SHIFT = 0x01      # --DB0: shift
 24
 25    LCD_ON_CTRL = 0x08          # DB3: turn lcd/cursor on
 26    LCD_ON_DISPLAY = 0x04       # --DB2: turn display on
 27    LCD_ON_CURSOR = 0x02        # --DB1: turn cursor on
 28    LCD_ON_BLINK = 0x01         # --DB0: blinking cursor
 29
 30    LCD_MOVE = 0x10             # DB4: move cursor/display
 31    LCD_MOVE_DISP = 0x08        # --DB3: move display (0-> move cursor)
 32    LCD_MOVE_RIGHT = 0x04       # --DB2: move right (0-> left)
 33
 34    LCD_FUNCTION = 0x20         # DB5: function set
 35    LCD_FUNCTION_8BIT = 0x10    # --DB4: set 8BIT mode (0->4BIT mode)
 36    LCD_FUNCTION_2LINES = 0x08  # --DB3: two lines (0->one line)
 37    LCD_FUNCTION_10DOTS = 0x04  # --DB2: 5x10 font (0->5x7 font)
 38    LCD_FUNCTION_RESET = 0x30   # See "Initializing by Instruction" section
 39
 40    LCD_CGRAM = 0x40            # DB6: set CG RAM address
 41    LCD_DDRAM = 0x80            # DB7: set DD RAM address
 42
 43    LCD_RS_CMD = 0
 44    LCD_RS_DATA = 1
 45
 46    LCD_RW_WRITE = 0
 47    LCD_RW_READ = 1
 48
 49    def __init__(self, num_lines, num_columns):
 50        self.num_lines = num_lines
 51        if self.num_lines > 4:
 52            self.num_lines = 4
 53        self.num_columns = num_columns
 54        if self.num_columns > 40:
 55            self.num_columns = 40
 56        self.cursor_x = 0
 57        self.cursor_y = 0
 58        self.implied_newline = False
 59        self.backlight = True
 60        self.display_off()
 61        self.backlight_on()
 62        self.clear()
 63        self.hal_write_command(self.LCD_ENTRY_MODE | self.LCD_ENTRY_INC)
 64        self.hide_cursor()
 65        self.display_on()
 66
 67    def clear(self):
 68        """Clears the LCD display and moves the cursor to the top left
 69        corner.
 70        """
 71        self.hal_write_command(self.LCD_CLR)
 72        self.hal_write_command(self.LCD_HOME)
 73        self.cursor_x = 0
 74        self.cursor_y = 0
 75
 76    def show_cursor(self):
 77        """Causes the cursor to be made visible."""
 78        self.hal_write_command(self.LCD_ON_CTRL | self.LCD_ON_DISPLAY |
 79                               self.LCD_ON_CURSOR)
 80
 81    def hide_cursor(self):
 82        """Causes the cursor to be hidden."""
 83        self.hal_write_command(self.LCD_ON_CTRL | self.LCD_ON_DISPLAY)
 84
 85    def blink_cursor_on(self):
 86        """Turns on the cursor, and makes it blink."""
 87        self.hal_write_command(self.LCD_ON_CTRL | self.LCD_ON_DISPLAY |
 88                               self.LCD_ON_CURSOR | self.LCD_ON_BLINK)
 89
 90    def blink_cursor_off(self):
 91        """Turns on the cursor, and makes it no blink (i.e. be solid)."""
 92        self.hal_write_command(self.LCD_ON_CTRL | self.LCD_ON_DISPLAY |
 93                               self.LCD_ON_CURSOR)
 94
 95    def display_on(self):
 96        """Turns on (i.e. unblanks) the LCD."""
 97        self.hal_write_command(self.LCD_ON_CTRL | self.LCD_ON_DISPLAY)
 98
 99    def display_off(self):
100        """Turns off (i.e. blanks) the LCD."""
101        self.hal_write_command(self.LCD_ON_CTRL)
102
103    def backlight_on(self):
104        """Turns the backlight on.
105        This isn't really an LCD command, but some modules have backlight
106        controls, so this allows the hal to pass through the command.
107        """
108        self.backlight = True
109        self.hal_backlight_on()
110
111    def backlight_off(self):
112        """Turns the backlight off.
113        This isn't really an LCD command, but some modules have backlight
114        controls, so this allows the hal to pass through the command.
115        """
116        self.backlight = False
117        self.hal_backlight_off()
118
119    def move_to(self, cursor_x, cursor_y):
120        """Moves the cursor position to the indicated position. The cursor
121        position is zero based (i.e. cursor_x == 0 indicates first column).
122        """
123        self.cursor_x = cursor_x
124        self.cursor_y = cursor_y
125        addr = cursor_x & 0x3f
126        if cursor_y & 1:
127            addr += 0x40    # Lines 1 & 3 add 0x40
128        if cursor_y & 2:    # Lines 2 & 3 add number of columns
129            addr += self.num_columns
130        self.hal_write_command(self.LCD_DDRAM | addr)
131
132    def putchar(self, char):
133        """Writes the indicated character to the LCD at the current cursor
134        position, and advances the cursor by one position.
135        """
136        if char == 'n':
137            if self.implied_newline:
138                # self.implied_newline means we advanced due to a wraparound,
139                # so if we get a newline right after that we ignore it.
140                pass
141            else:
142                self.cursor_x = self.num_columns
143        else:
144            self.hal_write_data(ord(char))
145            self.cursor_x += 1
146        if self.cursor_x >= self.num_columns:
147            self.cursor_x = 0
148            self.cursor_y += 1
149            self.implied_newline = (char != 'n')
150        if self.cursor_y >= self.num_lines:
151            self.cursor_y = 0
152        self.move_to(self.cursor_x, self.cursor_y)
153
154    def putstr(self, string):
155        """Write the indicated string to the LCD at the current cursor
156        position and advances the cursor position appropriately.
157        """
158        for char in string:
159            self.putchar(char)
160
161    def custom_char(self, location, charmap):
162        """Write a character to one of the 8 CGRAM locations, available
163        as chr(0) through chr(7).
164        """
165        location &= 0x7
166        self.hal_write_command(self.LCD_CGRAM | (location << 3))
167        self.hal_sleep_us(40)
168        for i in range(8):
169            self.hal_write_data(charmap[i])
170            self.hal_sleep_us(40)
171        self.move_to(self.cursor_x, self.cursor_y)
172
173    def hal_backlight_on(self):
174        """Allows the hal layer to turn the backlight on.
175        If desired, a derived HAL class will implement this function.
176        """
177        pass
178
179    def hal_backlight_off(self):
180        """Allows the hal layer to turn the backlight off.
181        If desired, a derived HAL class will implement this function.
182        """
183        pass
184
185    def hal_write_command(self, cmd):
186        """Write a command to the LCD.
187        It is expected that a derived HAL class will implement this
188        function.
189        """
190        raise NotImplementedError
191
192    def hal_write_data(self, data):
193        """Write data to the LCD.
194        It is expected that a derived HAL class will implement this
195        function.
196        """
197        raise NotImplementedError
198
199    def hal_sleep_us(self, usecs):
200        """Sleep for some time (given in microseconds)."""
201        time.sleep_us(usecs)

  1"""Implements a HD44780 character LCD connected via ESP32 GPIO pins."""
  2
  3from lcd_api import LcdApi
  4from machine import Pin
  5from utime import sleep_ms, sleep_us
  6
  7
  8class GpioLcd(LcdApi):
  9    """Implements a HD44780 character LCD connected via ESP32 GPIO pins."""
 10
 11    def __init__(self, rs_pin, enable_pin, d0_pin=None, d1_pin=None,
 12                 d2_pin=None, d3_pin=None, d4_pin=None, d5_pin=None,
 13                 d6_pin=None, d7_pin=None, rw_pin=None, backlight_pin=None,
 14                 num_lines=2, num_columns=16):
 15        """Constructs the GpioLcd object. All of the arguments must be machine.Pin
 16        objects which describe which pin the given line from the LCD is
 17        connected to.
 18        When used in 4-bit mode, only D4, D5, D6, and D7 are physically
 19        connected to the LCD panel. This function allows you call it like
 20        GpioLcd(rs, enable, D4, D5, D6, D7) and it will interpret that as
 21        if you had actually called:
 22        GpioLcd(rs, enable, d4=D4, d5=D5, d6=D6, d7=D7)
 23        The enable 8-bit mode, you need pass d0 through d7.
 24        The rw pin isn't used by this library, but if you specify it, then
 25        it will be set low.
 26        """
 27        self.rs_pin = rs_pin
 28        self.enable_pin = enable_pin
 29        self.rw_pin = rw_pin
 30        self.backlight_pin = backlight_pin
 31        self._4bit = True
 32        if d4_pin and d5_pin and d6_pin and d7_pin:
 33            self.d0_pin = d0_pin
 34            self.d1_pin = d1_pin
 35            self.d2_pin = d2_pin
 36            self.d3_pin = d3_pin
 37            self.d4_pin = d4_pin
 38            self.d5_pin = d5_pin
 39            self.d6_pin = d6_pin
 40            self.d7_pin = d7_pin
 41            if self.d0_pin and self.d1_pin and self.d2_pin and self.d3_pin:
 42                self._4bit = False
 43        else:
 44            # This is really 4-bit mode, and the 4 data pins were just
 45            # passed as the first 4 arguments, so we switch things around.
 46            self.d0_pin = None
 47            self.d1_pin = None
 48            self.d2_pin = None
 49            self.d3_pin = None
 50            self.d4_pin = d0_pin
 51            self.d5_pin = d1_pin
 52            self.d6_pin = d2_pin
 53            self.d7_pin = d3_pin
 54        self.rs_pin.init(Pin.OUT)
 55        self.rs_pin.value(0)
 56        if self.rw_pin:
 57            self.rw_pin.init(Pin.OUT)
 58            self.rw_pin.value(0)
 59        self.enable_pin.init(Pin.OUT)
 60        self.enable_pin.value(0)
 61        self.d4_pin.init(Pin.OUT)
 62        self.d5_pin.init(Pin.OUT)
 63        self.d6_pin.init(Pin.OUT)
 64        self.d7_pin.init(Pin.OUT)
 65        self.d4_pin.value(0)
 66        self.d5_pin.value(0)
 67        self.d6_pin.value(0)
 68        self.d7_pin.value(0)
 69        if not self._4bit:
 70            self.d0_pin.init(Pin.OUT)
 71            self.d1_pin.init(Pin.OUT)
 72            self.d2_pin.init(Pin.OUT)
 73            self.d3_pin.init(Pin.OUT)
 74            self.d0_pin.value(0)
 75            self.d1_pin.value(0)
 76            self.d2_pin.value(0)
 77            self.d3_pin.value(0)
 78        if self.backlight_pin is not None:
 79            self.backlight_pin.init(Pin.OUT)
 80            self.backlight_pin.value(0)
 81
 82        # See about splitting this into begin
 83
 84        sleep_ms(20)   # Allow LCD time to powerup
 85        # Send reset 3 times
 86        self.hal_write_init_nibble(self.LCD_FUNCTION_RESET)
 87        sleep_ms(5)    # need to delay at least 4.1 msec
 88        self.hal_write_init_nibble(self.LCD_FUNCTION_RESET)
 89        sleep_ms(1)
 90        self.hal_write_init_nibble(self.LCD_FUNCTION_RESET)
 91        sleep_ms(1)
 92        cmd = self.LCD_FUNCTION
 93        if not self._4bit:
 94            cmd |= self.LCD_FUNCTION_8BIT
 95        self.hal_write_init_nibble(cmd)
 96        sleep_ms(1)
 97        LcdApi.__init__(self, num_lines, num_columns)
 98        if num_lines > 1:
 99            cmd |= self.LCD_FUNCTION_2LINES
100        self.hal_write_command(cmd)
101
102    def hal_pulse_enable(self):
103        """Pulse the enable line high, and then low again."""
104        self.enable_pin.value(0)
105        sleep_us(1)
106        self.enable_pin.value(1)
107        sleep_us(1)       # Enable pulse needs to be > 450 nsec
108        self.enable_pin.value(0)
109        sleep_us(100)     # Commands need > 37us to settle
110
111    def hal_write_init_nibble(self, nibble):
112        """Writes an initialization nibble to the LCD.
113        This particular function is only used during initialization.
114        """
115        self.hal_write_4bits(nibble >> 4)
116
117    def hal_backlight_on(self):
118        """Allows the hal layer to turn the backlight on."""
119        if self.backlight_pin:
120            self.backlight_pin.value(1)
121
122    def hal_backlight_off(self):
123        """Allows the hal layer to turn the backlight off."""
124        if self.backlight_pin:
125            self.backlight_pin.value(0)
126
127    def hal_write_command(self, cmd):
128        """Writes a command to the LCD.
129        Data is latched on the falling edge of E.
130        """
131        self.rs_pin.value(0)
132        self.hal_write_8bits(cmd)
133        if cmd <= 3:
134            # The home and clear commands require a worst
135            # case delay of 4.1 msec
136            sleep_ms(5)
137
138    def hal_write_data(self, data):
139        """Write data to the LCD."""
140        self.rs_pin.value(1)
141        self.hal_write_8bits(data)
142
143    def hal_write_8bits(self, value):
144        """Writes 8 bits of data to the LCD."""
145        if self.rw_pin:
146            self.rw_pin.value(0)
147        if self._4bit:
148            self.hal_write_4bits(value >> 4)
149            self.hal_write_4bits(value)
150        else:
151            self.d3_pin.value(value & 0x08)
152            self.d2_pin.value(value & 0x04)
153            self.d1_pin.value(value & 0x02)
154            self.d0_pin.value(value & 0x01)
155            self.hal_write_4bits(value >> 4)
156
157    def hal_write_4bits(self, nibble):
158        """Writes 4 bits of data to the LCD."""
159        self.d7_pin.value(nibble & 0x08)
160        self.d6_pin.value(nibble & 0x04)
161        self.d5_pin.value(nibble & 0x02)
162        self.d4_pin.value(nibble & 0x01)
163        self.hal_pulse_enable()