[paolo192168]

Mi occupo della raspberry a tempo perso, ho fatto alcuni test come comandare rete ed e' tutto andato bene.
Ho di recente acquistato un display che si interfaccia con i2c, ho trafficato un po' ma non riesco a far scrivere nulla.
sudo i2cdetect -y 1
0 1 2 3 4 5 6 7 8 9 a b c d e f
00: -- -- -- -- -- -- -- -- -- -- -- -- --
10: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
20: -- -- -- -- -- -- -- 27 -- -- -- -- -- -- -- --
30: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
40: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
50: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
60: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
70: -- -- -- -- -- -- -- --
Questo é risultato del test (se sconnetto il display mi da --).

questo é il codice:
#--------------------------------------
import smbus
import time

# Define some device parameters
I2C_ADDR = 0x27 # I2C device address
LCD_WIDTH = 16 # Maximum characters per line

# Define some device constants
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
#LCD_BACKLIGHT = 0x00 # Off

ENABLE = 0b00000100 # Enable bit

# Timing constants
E_PULSE = 0.0005
E_DELAY = 0.0005

#Open I2C interface
#bus = smbus.SMBus(0) # Rev 1 Pi uses 0
bus = smbus.SMBus(1) # Rev 2 Pi uses 1

print ('ok smb bus')

def lcd_init():
# Initialise display
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):
# Send byte to data pins
# bits = the data
# mode = 1 for data
# 0 for command

bits_high = mode | (bits & 0xF0) | LCD_BACKLIGHT
bits_low = mode | ((bits<<4) & 0xF0) | LCD_BACKLIGHT

# High bits
bus.write_byte(I2C_ADDR, bits_high)
lcd_toggle_enable(bits_high)

# Low bits
bus.write_byte(I2C_ADDR, bits_low)
lcd_toggle_enable(bits_low)

def lcd_toggle_enable(bits):
# Toggle enable
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):
# Send string to display

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():
# Main program block

# Initialise display
lcd_init()

while True:
print ('ok while')
# Send some test
lcd_string("RPiSpy <",LCD_LINE_1)
lcd_string("I2C LCD <",LCD_LINE_2)

time.sleep(3)

# Send some more text
lcd_string("> RPiSpy",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)

Comincio a pensare che il display sia guasto.
Grazie a chi mi vorrà aiutare.

[paolo192168]

Mi rispondo da solo, il trimmer per il display era su 0!!!
Regolato il trimmer tutto funziona.
Grazie comunque.