A small, affordable computer with free resources to help people learn, make things, and have fun
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https://www.raspberrypi.org/forums/viewtopic.php?f=28&t=171288
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#!/usr/bin/python
import smbus
import time
I2C_ADDR = 0x27 # I2C device address
LCD_WIDTH = 16 # Maximum characters per line
LCD_CHR = 1 # Mode - Sending data
LCD_CMD = 0 # Mode - Sending command
LCD_LINE_1 = 0x80 # LCD RAM address for the 1st line
LCD_LINE_2 = 0xC0 # LCD RAM address for the 2nd line
LCD_LINE_3 = 0x94 # LCD RAM address for the 3rd line
LCD_LINE_4 = 0xD4 # LCD RAM address for the 4th line
LCD_BACKLIGHT = 0x08 # On
ENABLE = 0b00000100 # Enable bit
E_PULSE = 0.0005
E_DELAY = 0.0005
bus = smbus.SMBus(1) # Rev 2 Pi uses 1
def lcd_init():
lcd_byte(0x33,LCD_CMD) # 110011 Initialise
lcd_byte(0x32,LCD_CMD) # 110010 Initialise
lcd_byte(0x06,LCD_CMD) # 000110 Cursor move direction
lcd_byte(0x0C,LCD_CMD) # 001100 Display On,Cursor Off, Blink Off
lcd_byte(0x28,LCD_CMD) # 101000 Data length, number of lines, font size
lcd_byte(0x01,LCD_CMD) # 000001 Clear display
time.sleep(E_DELAY)
def lcd_byte(bits, mode):
bits_high = mode | (bits & 0xF0) | LCD_BACKLIGHT
bits_low = mode | ((bits<<4) & 0xF0) | LCD_BACKLIGHT
print '{0:8b}'.format(bits_high)
bus.write_byte(I2C_ADDR, bits_high)
lcd_toggle_enable(bits_high)
print '{0:8b}'.format(bits_low)
bus.write_byte(I2C_ADDR, bits_low)
lcd_toggle_enable(bits_low)
def lcd_toggle_enable(bits):
time.sleep(E_DELAY)
bus.write_byte(I2C_ADDR, (bits | ENABLE))
time.sleep(E_PULSE)
bus.write_byte(I2C_ADDR,(bits & ~ENABLE))
time.sleep(E_DELAY)
def lcd_string(message,line):
message = message.ljust(LCD_WIDTH," ")
lcd_byte(line, LCD_CMD)
for i in range(LCD_WIDTH):
lcd_byte(ord(message[i]),LCD_CHR)
def main():
lcd_init()
while True:
lcd_string("Line1 ---16CHARS",LCD_LINE_1)
lcd_string("I2C LCD ",LCD_LINE_2)
time.sleep(3)
# Send some more text
lcd_string("> Line1 ",LCD_LINE_1)
lcd_string("> I2C LCD",LCD_LINE_2)
time.sleep(3)
if __name__ == '__main__':
try:
main()
except KeyboardInterrupt:
pass
finally:
lcd_byte(0x01, LCD_CMD)
Dougie, I know you posted it a few months ago but I cannot get this program to work on Python 3, or is it a Python 2 program?DougieLawson wrote:Try this program to check whether your 16x2 LCD is working and wired correctly ...
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print '{0:8b}'.format(bits_high)Yes that is what I thought but I have added those and still cannot get it to work. Having said that though, I have a 20 x 4 LCD so that could now be why. Just wanted to eliminate one thing at a time. Thanks.scotty101 wrote:Looks like python2 given the missing parenthesis for print.
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0 1 2 3 4 5 6 7 8 9 a b c d e f
00: -- -- -- -- -- -- -- -- -- -- -- -- --
10: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
20: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
30: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 3f
40: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
50: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
60: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
70: -- -- -- -- -- -- -- -- Code: Select all
111000
1000
Traceback (most recent call last):
File "/home/pi/I2C Python 2 program.py", line 79, in <module>
lcd_byte(0x01, LCD_CMD)
File "/home/pi/I2C Python 2 program.py", line 38, in lcd_byte
bus.write_byte(I2C_ADDR, bits_high)
IOError: [Errno 5] Input/output errorCode: Select all
I2C_ADDR = 0x27 # I2C device addressCode: Select all
I2C_ADDR = 0x3F # I2C device addressThank you. That has made a difference but although there are now no errors, it has just produced a (seemingly) never ending list of binary? on the screen but nothing on the LCD. The following is just a small sample and it was continuing until I pressed CTRL-C.DougieLawson wrote:You need a quick tweak to my sample python2 program
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111000
111000
111000
101000
1000
1101000
1000
11001000
101000
10001000
1000
11000
10001000Ha Ha,DougieLawson wrote:The more important test involves a pair of MK I eyeballs and the LCD you're trying to drive.