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| 1 | +"""Provides an API for talking to HD44780 compatible character LCDs.""" |
| 2 | + |
| 3 | +import time |
| 4 | + |
| 5 | +class 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 | +
|
| 10 | + It is expected that a derived class will implement the hal_xxx functions. |
| 11 | + """ |
| 12 | + |
| 13 | + # The following constant names were lifted from the avrlib lcd.h |
| 14 | + # header file, however, I changed the definitions from bit numbers |
| 15 | + # to bit masks. |
| 16 | + # |
| 17 | + # HD44780 LCD controller command set |
| 18 | + |
| 19 | + LCD_CLR = 0x01 # DB0: clear display |
| 20 | + LCD_HOME = 0x02 # DB1: return to home position |
| 21 | + |
| 22 | + LCD_ENTRY_MODE = 0x04 # DB2: set entry mode |
| 23 | + LCD_ENTRY_INC = 0x02 # --DB1: increment |
| 24 | + LCD_ENTRY_SHIFT = 0x01 # --DB0: shift |
| 25 | + |
| 26 | + LCD_ON_CTRL = 0x08 # DB3: turn lcd/cursor on |
| 27 | + LCD_ON_DISPLAY = 0x04 # --DB2: turn display on |
| 28 | + LCD_ON_CURSOR = 0x02 # --DB1: turn cursor on |
| 29 | + LCD_ON_BLINK = 0x01 # --DB0: blinking cursor |
| 30 | + |
| 31 | + LCD_MOVE = 0x10 # DB4: move cursor/display |
| 32 | + LCD_MOVE_DISP = 0x08 # --DB3: move display (0-> move cursor) |
| 33 | + LCD_MOVE_RIGHT = 0x04 # --DB2: move right (0-> left) |
| 34 | + |
| 35 | + LCD_FUNCTION = 0x20 # DB5: function set |
| 36 | + LCD_FUNCTION_8BIT = 0x10 # --DB4: set 8BIT mode (0->4BIT mode) |
| 37 | + LCD_FUNCTION_2LINES = 0x08 # --DB3: two lines (0->one line) |
| 38 | + LCD_FUNCTION_10DOTS = 0x04 # --DB2: 5x10 font (0->5x7 font) |
| 39 | + LCD_FUNCTION_RESET = 0x30 # See "Initializing by Instruction" section |
| 40 | + |
| 41 | + LCD_CGRAM = 0x40 # DB6: set CG RAM address |
| 42 | + LCD_DDRAM = 0x80 # DB7: set DD RAM address |
| 43 | + |
| 44 | + LCD_RS_CMD = 0 |
| 45 | + LCD_RS_DATA = 1 |
| 46 | + |
| 47 | + LCD_RW_WRITE = 0 |
| 48 | + LCD_RW_READ = 1 |
| 49 | + |
| 50 | + def __init__(self, num_lines, num_columns): |
| 51 | + self.num_lines = num_lines |
| 52 | + if self.num_lines > 4: |
| 53 | + self.num_lines = 4 |
| 54 | + self.num_columns = num_columns |
| 55 | + if self.num_columns > 40: |
| 56 | + self.num_columns = 40 |
| 57 | + self.cursor_x = 0 |
| 58 | + self.cursor_y = 0 |
| 59 | + self.implied_newline = False |
| 60 | + self.backlight = True |
| 61 | + self.display_off() |
| 62 | + self.backlight_on() |
| 63 | + self.clear() |
| 64 | + self.hal_write_command(self.LCD_ENTRY_MODE | self.LCD_ENTRY_INC) |
| 65 | + self.hide_cursor() |
| 66 | + self.display_on() |
| 67 | + |
| 68 | + def clear(self): |
| 69 | + """Clears the LCD display and moves the cursor to the top left |
| 70 | + corner. |
| 71 | + """ |
| 72 | + self.hal_write_command(self.LCD_CLR) |
| 73 | + self.hal_write_command(self.LCD_HOME) |
| 74 | + self.cursor_x = 0 |
| 75 | + self.cursor_y = 0 |
| 76 | + |
| 77 | + def show_cursor(self): |
| 78 | + """Causes the cursor to be made visible.""" |
| 79 | + self.hal_write_command(self.LCD_ON_CTRL | self.LCD_ON_DISPLAY | |
| 80 | + self.LCD_ON_CURSOR) |
| 81 | + |
| 82 | + def hide_cursor(self): |
| 83 | + """Causes the cursor to be hidden.""" |
| 84 | + self.hal_write_command(self.LCD_ON_CTRL | self.LCD_ON_DISPLAY) |
| 85 | + |
| 86 | + def blink_cursor_on(self): |
| 87 | + """Turns on the cursor, and makes it blink.""" |
| 88 | + self.hal_write_command(self.LCD_ON_CTRL | self.LCD_ON_DISPLAY | |
| 89 | + self.LCD_ON_CURSOR | self.LCD_ON_BLINK) |
| 90 | + |
| 91 | + def blink_cursor_off(self): |
| 92 | + """Turns on the cursor, and makes it no blink (i.e. be solid).""" |
| 93 | + self.hal_write_command(self.LCD_ON_CTRL | self.LCD_ON_DISPLAY | |
| 94 | + self.LCD_ON_CURSOR) |
| 95 | + |
| 96 | + def display_on(self): |
| 97 | + """Turns on (i.e. unblanks) the LCD.""" |
| 98 | + self.hal_write_command(self.LCD_ON_CTRL | self.LCD_ON_DISPLAY) |
| 99 | + |
| 100 | + def display_off(self): |
| 101 | + """Turns off (i.e. blanks) the LCD.""" |
| 102 | + self.hal_write_command(self.LCD_ON_CTRL) |
| 103 | + |
| 104 | + def backlight_on(self): |
| 105 | + """Turns the backlight on. |
| 106 | +
|
| 107 | + This isn't really an LCD command, but some modules have backlight |
| 108 | + controls, so this allows the hal to pass through the command. |
| 109 | + """ |
| 110 | + self.backlight = True |
| 111 | + self.hal_backlight_on() |
| 112 | + |
| 113 | + def backlight_off(self): |
| 114 | + """Turns the backlight off. |
| 115 | +
|
| 116 | + This isn't really an LCD command, but some modules have backlight |
| 117 | + controls, so this allows the hal to pass through the command. |
| 118 | + """ |
| 119 | + self.backlight = False |
| 120 | + self.hal_backlight_off() |
| 121 | + |
| 122 | + def move_to(self, cursor_x, cursor_y): |
| 123 | + """Moves the cursor position to the indicated position. The cursor |
| 124 | + position is zero based (i.e. cursor_x == 0 indicates first column). |
| 125 | + """ |
| 126 | + self.cursor_x = cursor_x |
| 127 | + self.cursor_y = cursor_y |
| 128 | + addr = cursor_x & 0x3f |
| 129 | + if cursor_y & 1: |
| 130 | + addr += 0x40 # Lines 1 & 3 add 0x40 |
| 131 | + if cursor_y & 2: # Lines 2 & 3 add number of columns |
| 132 | + addr += self.num_columns |
| 133 | + self.hal_write_command(self.LCD_DDRAM | addr) |
| 134 | + |
| 135 | + def putchar(self, char): |
| 136 | + """Writes the indicated character to the LCD at the current cursor |
| 137 | + position, and advances the cursor by one position. |
| 138 | + """ |
| 139 | + if char == '\n': |
| 140 | + if self.implied_newline: |
| 141 | + # self.implied_newline means we advanced due to a wraparound, |
| 142 | + # so if we get a newline right after that we ignore it. |
| 143 | + self.implied_newline = False |
| 144 | + else: |
| 145 | + self.cursor_x = self.num_columns |
| 146 | + else: |
| 147 | + self.hal_write_data(ord(char)) |
| 148 | + self.cursor_x += 1 |
| 149 | + if self.cursor_x >= self.num_columns: |
| 150 | + self.cursor_x = 0 |
| 151 | + self.cursor_y += 1 |
| 152 | + self.implied_newline = (char != '\n') |
| 153 | + if self.cursor_y >= self.num_lines: |
| 154 | + self.cursor_y = 0 |
| 155 | + self.move_to(self.cursor_x, self.cursor_y) |
| 156 | + |
| 157 | + def putstr(self, string): |
| 158 | + """Write the indicated string to the LCD at the current cursor |
| 159 | + position and advances the cursor position appropriately. |
| 160 | + """ |
| 161 | + for char in string: |
| 162 | + self.putchar(char) |
| 163 | + |
| 164 | + def custom_char(self, location, charmap): |
| 165 | + """Write a character to one of the 8 CGRAM locations, available |
| 166 | + as chr(0) through chr(7). |
| 167 | + """ |
| 168 | + location &= 0x7 |
| 169 | + self.hal_write_command(self.LCD_CGRAM | (location << 3)) |
| 170 | + self.hal_sleep_us(40) |
| 171 | + for i in range(8): |
| 172 | + self.hal_write_data(charmap[i]) |
| 173 | + self.hal_sleep_us(40) |
| 174 | + self.move_to(self.cursor_x, self.cursor_y) |
| 175 | + |
| 176 | + def hal_backlight_on(self): |
| 177 | + """Allows the hal layer to turn the backlight on. |
| 178 | +
|
| 179 | + If desired, a derived HAL class will implement this function. |
| 180 | + """ |
| 181 | + pass |
| 182 | + |
| 183 | + def hal_backlight_off(self): |
| 184 | + """Allows the hal layer to turn the backlight off. |
| 185 | +
|
| 186 | + If desired, a derived HAL class will implement this function. |
| 187 | + """ |
| 188 | + pass |
| 189 | + |
| 190 | + def hal_write_command(self, cmd): |
| 191 | + """Write a command to the LCD. |
| 192 | +
|
| 193 | + It is expected that a derived HAL class will implement this |
| 194 | + function. |
| 195 | + """ |
| 196 | + raise NotImplementedError |
| 197 | + |
| 198 | + def hal_write_data(self, data): |
| 199 | + """Write data to the LCD. |
| 200 | +
|
| 201 | + It is expected that a derived HAL class will implement this |
| 202 | + function. |
| 203 | + """ |
| 204 | + raise NotImplementedError |
| 205 | + |
| 206 | + # This is a default implementation of hal_sleep_us which is suitable |
| 207 | + # for most micropython implementations. For platforms which don't |
| 208 | + # support `time.sleep_us()` they should provide their own implementation |
| 209 | + # of hal_sleep_us in their hal layer and it will be used instead. |
| 210 | + def hal_sleep_us(self, usecs): |
| 211 | + """Sleep for some time (given in microseconds).""" |
| 212 | + time.sleep_us(usecs) # NOTE this is not part of Standard Python library, specific hal layers will need to override this |
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