16x2 LCD Display graphics

[Vishruth_kumar]

I am using Adafruit Library to display the instantaneous values of LDR on 16x2 LCD screen . The Adafruit libarary;'s code is:

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from time import sleep


class Adafruit_CharLCD(object):

    # commands
    LCD_CLEARDISPLAY        = 0x01
    LCD_RETURNHOME          = 0x02
    LCD_ENTRYMODESET        = 0x04
    LCD_DISPLAYCONTROL      = 0x08
    LCD_CURSORSHIFT         = 0x10
    LCD_FUNCTIONSET         = 0x20
    LCD_SETCGRAMADDR        = 0x40
    LCD_SETDDRAMADDR        = 0x80

    # flags for display entry mode
    LCD_ENTRYRIGHT          = 0x00
    LCD_ENTRYLEFT           = 0x02
    LCD_ENTRYSHIFTINCREMENT = 0x01
    LCD_ENTRYSHIFTDECREMENT = 0x00

    # flags for display on/off control
    LCD_DISPLAYON           = 0x04
    LCD_DISPLAYOFF          = 0x00
    LCD_CURSORON            = 0x02
    LCD_CURSOROFF           = 0x00
    LCD_BLINKON             = 0x01
    LCD_BLINKOFF            = 0x00

    # flags for display/cursor shift
    LCD_DISPLAYMOVE         = 0x08
    LCD_CURSORMOVE          = 0x00

    # flags for display/cursor shift
    LCD_DISPLAYMOVE         = 0x08
    LCD_CURSORMOVE          = 0x00
    LCD_MOVERIGHT           = 0x04
    LCD_MOVELEFT            = 0x00

    # flags for function set
    LCD_8BITMODE            = 0x10
    LCD_4BITMODE            = 0x00
    LCD_2LINE               = 0x08
    LCD_1LINE               = 0x00
    LCD_5x10DOTS            = 0x04
    LCD_5x8DOTS             = 0x00

    def __init__(self, pin_rs=7, pin_e=8, pins_db=[25, 24, 23, 18], GPIO=None):
        # Emulate the old behavior of using RPi.GPIO if we haven't been given
        # an explicit GPIO interface to use
        if not GPIO:
            import RPi.GPIO as GPIO
            GPIO.setwarnings(False)
        self.GPIO = GPIO
        self.pin_rs = pin_rs
        self.pin_e = pin_e
        self.pins_db = pins_db

        self.GPIO.setmode(GPIO.BCM)
        self.GPIO.setup(self.pin_e, GPIO.OUT)
        self.GPIO.setup(self.pin_rs, GPIO.OUT)

        for pin in self.pins_db:
            self.GPIO.setup(pin, GPIO.OUT)

        self.write4bits(0x33)  # initialization
        self.write4bits(0x32)  # initialization
        self.write4bits(0x28)  # 2 line 5x7 matrix
        self.write4bits(0x0C)  # turn cursor off 0x0E to enable cursor
        self.write4bits(0x06)  # shift cursor right

        self.displaycontrol = self.LCD_DISPLAYON | self.LCD_CURSOROFF | self.LCD_BLINKOFF

        self.displayfunction = self.LCD_4BITMODE | self.LCD_1LINE | self.LCD_5x8DOTS
        self.displayfunction |= self.LCD_2LINE

        # Initialize to default text direction (for romance languages)
        self.displaymode = self.LCD_ENTRYLEFT | self.LCD_ENTRYSHIFTDECREMENT
        self.write4bits(self.LCD_ENTRYMODESET | self.displaymode)  # set the entry mode

        self.clear()

    def begin(self, cols, lines):
        if (lines > 1):
            self.numlines = lines
            self.displayfunction |= self.LCD_2LINE

    def home(self):
        self.write4bits(self.LCD_RETURNHOME)  # set cursor position to zero
        self.delayMicroseconds(3000)  # this command takes a long time!

    def clear(self):
        self.write4bits(self.LCD_CLEARDISPLAY)  # command to clear display
        self.delayMicroseconds(3000)  # 3000 microsecond sleep, clearing the display takes a long time

    def setCursor(self, col, row):
        self.row_offsets = [0x00, 0x40, 0x14, 0x54]
        if row > self.numlines:
            row = self.numlines - 1  # we count rows starting w/0
        self.write4bits(self.LCD_SETDDRAMADDR | (col + self.row_offsets[row]))

    def noDisplay(self):
        """ Turn the display off (quickly) """
        self.displaycontrol &= ~self.LCD_DISPLAYON
        self.write4bits(self.LCD_DISPLAYCONTROL | self.displaycontrol)

    def display(self):
        """ Turn the display on (quickly) """
        self.displaycontrol |= self.LCD_DISPLAYON
        self.write4bits(self.LCD_DISPLAYCONTROL | self.displaycontrol)

    def noCursor(self):
        """ Turns the underline cursor off """
        self.displaycontrol &= ~self.LCD_CURSORON
        self.write4bits(self.LCD_DISPLAYCONTROL | self.displaycontrol)

    def cursor(self):
        """ Turns the underline cursor on """
        self.displaycontrol |= self.LCD_CURSORON
        self.write4bits(self.LCD_DISPLAYCONTROL | self.displaycontrol)

    def noBlink(self):
        """ Turn the blinking cursor off """
        self.displaycontrol &= ~self.LCD_BLINKON
        self.write4bits(self.LCD_DISPLAYCONTROL | self.displaycontrol)

    def blink(self):
        """ Turn the blinking cursor on """
        self.displaycontrol |= self.LCD_BLINKON
        self.write4bits(self.LCD_DISPLAYCONTROL | self.displaycontrol)

    def DisplayLeft(self):
        """ These commands scroll the display without changing the RAM """
        self.write4bits(self.LCD_CURSORSHIFT | self.LCD_DISPLAYMOVE | self.LCD_MOVELEFT)

    def scrollDisplayRight(self):
        """ These commands scroll the display without changing the RAM """
        self.write4bits(self.LCD_CURSORSHIFT | self.LCD_DISPLAYMOVE | self.LCD_MOVERIGHT)

    def leftToRight(self):
        """ This is for text that flows Left to Right """
        self.displaymode |= self.LCD_ENTRYLEFT
        self.write4bits(self.LCD_ENTRYMODESET | self.displaymode)

    def rightToLeft(self):
        """ This is for text that flows Right to Left """
        self.displaymode &= ~self.LCD_ENTRYLEFT
        self.write4bits(self.LCD_ENTRYMODESET | self.displaymode)

    def autoscroll(self):
        """ This will 'right justify' text from the cursor """
        self.displaymode |= self.LCD_ENTRYSHIFTINCREMENT
        self.write4bits(self.LCD_ENTRYMODESET | self.displaymode)

    def noAutoscroll(self):
        """ This will 'left justify' text from the cursor """
        self.displaymode &= ~self.LCD_ENTRYSHIFTINCREMENT
        self.write4bits(self.LCD_ENTRYMODESET | self.displaymode)

    def write4bits(self, bits, char_mode=False):
        """ Send command to LCD """
        self.delayMicroseconds(1000)  # 1000 microsecond sleep
        bits = bin(bits)[2:].zfill(8)
        self.GPIO.output(self.pin_rs, char_mode)
        for pin in self.pins_db:
            self.GPIO.output(pin, False)
        for i in range(4):
            if bits[i] == "1":
                self.GPIO.output(self.pins_db[::-1][i], True)
        self.pulseEnable()
        for pin in self.pins_db:
            self.GPIO.output(pin, False)
        for i in range(4, 8):
            if bits[i] == "1":
                self.GPIO.output(self.pins_db[::-1][i-4], True)
        self.pulseEnable()

    def delayMicroseconds(self, microseconds):
        seconds = microseconds / float(1000000)  # divide microseconds by 1 million for seconds
        sleep(seconds)

    def pulseEnable(self):
        self.GPIO.output(self.pin_e, False)
        self.delayMicroseconds(1)       # 1 microsecond pause - enable pulse must be > 450ns
        self.GPIO.output(self.pin_e, True)
        self.delayMicroseconds(1)       # 1 microsecond pause - enable pulse must be > 450ns
        self.GPIO.output(self.pin_e, False)
        self.delayMicroseconds(1)       # commands need > 37us to settle

    def message(self, text):
        """ Send string to LCD. Newline wraps to second line"""
        for char in text:
            if char == '\n':
                self.write4bits(0xC0)  # next line
            else:
                self.write4bits(ord(char), True)

The main part of program is:

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from Adafruit_CharLCD import Adafruit_CharLCD
import RPi.GPIO as GPIO
import time
lcd = Adafruit_CharLCD()
lcd.clear()

GPIO.setmode(GPIO.BCM)
pin_to_circuit = 4
def rc_time (pin_to_circuit):
     count = 0
  
     #Output on the pin for 
     GPIO.setup(pin_to_circuit, GPIO.OUT)
     GPIO.output(pin_to_circuit, GPIO.LOW)
     time.sleep(0.5)

     # Change the pin back to input
     GPIO.setup(pin_to_circuit, GPIO.IN)
  
     #Count until the pin goes high
     while (GPIO.input(pin_to_circuit) == GPIO.LOW):
        count += 1

     return count

 #Catch when script is interrupted, cleanup correctly
try:
    # Main loop
    while True:
        
        print rc_time(pin_to_circuit)
        lcd.clear()
        lcd.message('LDR Reading:')
        lcd.message(str(rc_time(pin_to_circuit)))
        
       
except KeyboardInterrupt:
    pass
finally:
    GPIO.cleanup()

The program is working properly by displaying the LDR's reading after every 500 micro seconds. I want to convert this data in bar graphics form like the one we see while changing the sound volume of any device.
Is that possible?
I am new to python programming , Can somebody help me with the code??
Thank you!!

[elParaguayo]

My volume display on an LCD looks something like this:

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-|XXXXXX----|+

where the "X" is a solid block.

You can get a solid block on the LCD by using chr(255) in your string.

This is my volume change function: https://github.com/elParaguayo/PiRadio/ ... io.py#L162

It's this function that creates the number of square blocks for my volume display.

The final bit is formatted by my LCD module. I've defined some templates for the display and one of the lines (https://github.com/elParaguayo/PiRadio/ ... lay.py#L64) displays the volume with the "{vol}" bit being replaced by the output of the formula above.

To be honest, you're best ignoring that last bit and just concentrating on the function that creates a number of square blocks (between 0-10) depending on the volume level.

[Vishruth_kumar]

it works , thank you!

[DougieLawson]

If you use

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    def create_char(self, location, pattern):
        """Fill one of the first 8 CGRAM locations with custom characters.
        The location parameter should be between 0 and 7 and pattern should
        provide an array of 8 bytes containing the pattern. E.g. you can easyly
        design your custom character at http://www.quinapalus.com/hd44780udg.html
        To show your custom character use eg. lcd.message('\x01')
        """

You can create the 1/5, 2/5, 3/5 & 4/5 custom characters to get better precision on your display.

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x.... xx... xxx.. xxxx.
x.... xx... xxx.. xxxx.
x.... xx... xxx.. xxxx.
x.... xx... xxx.. xxxx.
x.... xx... xxx.. xxxx.
x.... xx... xxx.. xxxx.
x.... xx... xxx.. xxxx.
..... ..... ..... .....

The patterns for those are

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0x10, 0x18, 0x1C, 0x1E

repeated for seven lines.

[elParaguayo]

Yes. I've been meaning to try that out.

[elParaguayo]

Seems to work nicely:

(Apologies for the shaky hands).

FYI I'm not actually using the Adafruit library but I'm doing exactly the same thing!