tdack · August 29, 2015 14:06 · Jul 27, 2013
diff --git a/lcdui.py b/lcdui.py
@@ -0,0 +1,256 @@
+import smbus
+import getopt
+import sys
+from time import *
+from time import gmtime, strftime
+
+# TODO: Factor out all device_write calls to some PCF8574 specific module ... 
+#       will be different with another io expander
+
+# communication from expander to display: high nibble first, then low nibble
+# communication via i2c to the PCF 8547: bits are processed from highest to lowest (send P7 bit first) 
+
+
+# General i2c device class so that other devices can be added easily
+class i2c_device:
+    def __init__(self, addr, port):
+        self.addr = addr
+        self.bus = smbus.SMBus(port)
+
+    def write(self, byte):
+        self.bus.write_byte(self.addr, byte)
+
+    def read(self):
+        return self.bus.read_byte(self.addr)
+
+    def read_nbytes_data(self, data, n): # For sequential reads > 1 byte
+        return self.bus.read_i2c_block_data(self.addr, data, n)
+
+
+class ioexpander:
+    def __init__(self):
+        pass
+
+class lcd:
+    #initializes objects and lcd
+
+    # LCD 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 on/off control
+    LCD_DISPLAYON           = 0x04
+    LCD_DISPLAYOFF          = 0x00
+    LCD_CURSORON            = 0x02
+    LCD_CURSOROFF           = 0x00
+    LCD_BLINKON             = 0x01
+    LCD_BLINKOFF            = 0x00
+
+    # Flags for display entry mode
+    LCD_ENTRYRIGHT          = 0x00
+    LCD_ENTRYLEFT           = 0x02
+    LCD_ENTRYSHIFTINCREMENT = 0x01
+    LCD_ENTRYSHIFTDECREMENT = 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
+
+    # flags for backlight control
+    LCD_BACKLIGHT = 0x08
+    LCD_NOBACKLIGHT = 0x00
+
+    EN = 0b00000100  # Enable bit
+    RW = 0b00000010  # Read/Write bit
+    RS = 0b00000001  # Register select bit
+
+
+
+    '''
+    new pinout:
+    ----------
+0x80    P7 -  - D7     
+0x40    P6 -  - D6
+0x20    P5 -  - D5
+0x10    P4 -  - D4    
+    -----------
+0x08    P3 -  - BL   Backlight ???
+0x04    P2 -  - EN   Starts Data read/write 
+0x02    P1 -  - RW   low: write, high: read   
+0x01    P0 -  - RS   Register Select: 0: Instruction Register (IR) (AC when read), 1: data register (DR)
+    '''
+
+    def __init__(self, addr, port, withBacklight=True, withOneTimeInit=False):
+        '''
+        device writes!
+        crosscheck also http://www.monkeyboard.org/tutorials/81-display/70-usb-serial-to-hd44780-lcd
+        here a sequence is listed
+        '''
+        self.displayshift   = (self.LCD_CURSORMOVE |
+                               self.LCD_MOVERIGHT)
+        self.displaymode    = (self.LCD_ENTRYLEFT |
+                               self.LCD_ENTRYSHIFTDECREMENT)
+        self.displaycontrol = (self.LCD_DISPLAYON |
+                               self.LCD_CURSOROFF |
+                               self.LCD_BLINKOFF)
+
+
+        if withBacklight:
+            self.blFlag=self.LCD_BACKLIGHT
+        else:
+            self.blFlag=self.LCD_NOBACKLIGHT
+
+
+        self.lcd_device = i2c_device(addr, port)
+
+        # we can initialize the display only once after it had been powered on
+        if(withOneTimeInit):
+            self.lcd_device.write(0x20) 
+            self.lcd_strobe()
+            sleep(0.0100) # TODO: Not clear if we have to wait that long
+            self.lcd_write(self.LCD_FUNCTIONSET | self.LCD_4BITMODE  | self.LCD_2LINE | self.LCD_5x8DOTS) # 0x28
+
+        self.lcd_write(self.LCD_DISPLAYCONTROL | self.displaycontrol)   # 0x08 + 0x4 = 0x0C
+        self.lcd_write(self.LCD_ENTRYMODESET   | self.displaymode)      # 0x06
+        self.lcd_write(self.LCD_CLEARDISPLAY)                           # 0x01
+        self.lcd_write(self.LCD_CURSORSHIFT    | self.displayshift)     # 0x14 
+        self.lcd_write(self.LCD_RETURNHOME)
+
+
+    # clocks EN to latch command
+    def lcd_strobe(self):
+        self.lcd_device.write((self.lcd_device.read() | self.EN | self.blFlag)) # | 0b0000 0100 # set "EN" high
+        self.lcd_device.write(( (self.lcd_device.read() | self.blFlag) & 0xFB)) # & 0b1111 1011 # set "EN" low
+
+    # write data to lcd in 4 bit mode, 2 nibbles
+    # high nibble is sent first
+    def lcd_write(self, cmd):
+
+        #write high nibble first
+        self.lcd_device.write( (cmd & 0xF0) | self.blFlag )
+        hi= self.lcd_device.read()
+        self.lcd_strobe()
+
+        # write low nibble second ...
+        self.lcd_device.write( (cmd << 4) | self.blFlag )
+        lo= self.lcd_device.read()
+        self.lcd_strobe()
+        self.lcd_device.write(self.blFlag)
+
+
+    # write a character to lcd (or character rom) 0x09: backlight | RS=DR
+    # works as expected
+    def lcd_write_char(self, charvalue):
+        controlFlag = self.blFlag | self.RS
+
+        # write high nibble
+        self.lcd_device.write((controlFlag | (charvalue & 0xF0)))
+        self.lcd_strobe()
+
+        # write low nibble
+        self.lcd_device.write((controlFlag | (charvalue << 4)))
+        self.lcd_strobe()
+        self.lcd_device.write(self.blFlag)
+
+
+    # put char function
+    def lcd_putc(self, char):
+        self.lcd_write_char(ord(char))
+
+    def _setDDRAMAdress(self, line, col):
+        # we write to the Data Display RAM (DDRAM)        
+        # TODO: Factor line offsets for other display organizations; this is for 20x4 only 
+        if line == 1:
+            self.lcd_write(self.LCD_SETDDRAMADDR | (0x00 + col) )
+        if line == 2:
+            self.lcd_write(self.LCD_SETDDRAMADDR | (0x40 + col) )
+        if line == 3:
+            self.lcd_write(self.LCD_SETDDRAMADDR | (0x14 + col) )
+        if line == 4:
+            self.lcd_write(self.LCD_SETDDRAMADDR | (0x54 + col) )
+
+
+    # put string function
+    def lcd_puts(self, string, line):
+        self._setDDRAMAdress(line, 0)
+        for char in string:
+            self.lcd_putc(char)
+
+    # clear lcd and set to home
+    def lcd_clear(self):
+        # self.lcd_write(0x10)
+        self.lcd_write(self.LCD_CLEARDISPLAY)
+        # self.lcd_write(0x20)
+        self.lcd_write(self.LCD_RETURNHOME)
+
+    # add custom characters (0 - 7)
+    def lcd_load_custon_chars(self, fontdata):
+        self.lcd_device.bus.write(0x40);
+        for char in fontdata:
+            for line in char:
+                self.lcd_write_char(line)
+
+# Let them know how it works
+def usage():
+    print 'Usage: lcdui.py --init --debug --backlightoff'
+
+# Handle the command line arguments
+def main():    
+    initFlag=False
+    debug=False
+    backlight=True
+
+    try:
+        opts, args = getopt.getopt(sys.argv[1:],"idb",["init","debug","backlightoff"])
+
+    except getopt.GetoptError:
+        usage()
+        sys.exit(2)
+
+
+    for opt, arg in opts:
+        if opt == '-h':
+            usage()
+            sys.exit()
+        elif opt in ("-i", "--init"):
+            initFlag = True
+        elif opt in ("-d", "--debug"):
+            debug = True
+        elif opt in ("-b", "--backlightoff"):
+            backlight = False
+
+    if initFlag:
+        print "Doing initial init ..."
+    else:
+        print "Skipping init ..."
+
+    device = lcd(0x27,1,backlight, initFlag)  
+    device.lcd_puts("01234567890123456789",1)
+    device.lcd_puts("012345 Zeile 2 56789",2)
+    device.lcd_puts("012345 Zeile 3 56789",3)
+    device.lcd_puts(strftime("%Y-%m-%d %H:%M:%S", gmtime()),4)
+    sleep(3)
+    device.lcd_clear()
+    device.lcd_puts("    Simple Clock    ",1)
+    while True:
+        device.lcd_puts(strftime("%Y-%m-%d %H:%M:%S ", gmtime()),3)
+        sleep(1)
+
+if __name__ == '__main__':
+    main()
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