WiringPi-Pythonを使ってI2C キャラクタLCDのAQM0802Aを使ってみる。
I2Cの準備
I2C deviceの有効化
I2Cデバイスが有効になっていることを確認する。
$ cat /etc/modules
...
i2c-dev
...
$ lsmod
...
i2c_dev 6047 0
i2c_bcm2708 5014 0
...
i2c-tools
I2C toolsをインストールして、slave addressを確認する。AQM0802Aのslave addressは0x3e。
$ sudo apt-get install i2c-tools
$ i2cdetect -y 1
0 1 2 3 4 5 6 7 8 9 a b c d e f
00: -- -- -- -- -- -- -- -- -- -- -- -- --
10: -- -- -- -- -- -- -- -- -- -- -- UU -- -- -- --
20: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
30: -- -- -- -- -- -- -- -- -- -- -- -- -- -- 3e --
40: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
50: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
60: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
70: -- -- -- -- -- -- -- --
LCD制御モジュール
Wiring Piを使ってLCD表示を制御するモジュールを作成する。
本当はInstructionの間には実行時間を考慮したwaitが必要だが、clear/home以外はμs単位なのでとりあえず無視。
st7032i.py
#!/usr/bin/env python3
# -*- coding:utf-8 -*-
"""
ST7032i LCD driver control library
"""
import wiringpi2 as wp
import time
I2C_ADDR = 0x3e
class St7032iLCD:
"""
ST7032i LCD control class
"""
def __init__(self, i2c_addr = I2C_ADDR):
self.i2c = wp.I2C()
self.fd = self.i2c.setup(i2c_addr)
self._init()
def _init(self):
self.write_instruction(0x38) # function set: 8 bit, 2 line
self.write_instruction(0x39) # function set: 8 bit, 2 line, IS=1
self.write_instruction(0x14) # internal OSC freq
self.write_instruction(0x70) # contrast set
self.write_instruction(0x56) # Power/ICON/Constrast
self.write_instruction(0x6c) # Follower control
time.sleep(0.2) # wait time > 200 ms
self.write_instruction(0x38) # function set: 8 bit, 2 line, IS=0
self.write_instruction(0x06) # Entry mode set
self.write_instruction(0x0c) # Display on/off
self.write_instruction(0x01) # Clear display
time.sleep(0.01) # wait time > 1.08 ms
self.write_instruction(0x02) # return home
time.sleep(0.01) # wait time > 1.08 ms
def _write(self, control, data):
self.i2c.writeReg8(self.fd, control, data)
def write_instruction(self, data):
""" Send Instruction code. """
self._write(0x00, data)
def write_data(self, data):
""" Send data into data register. """
self._write(0x40, data)
def clear(self):
""" Clear display and return to home position. """
self.write_instruction(0x01) # clear display
time.sleep(0.01) # wait time > 1.08 ms
self.write_instruction(0x02) # return home
time.sleep(0.01) # wait time > 1.08 ms
def return_home(self):
""" return to home """
self.write_instruction(0x02) # return home
time.sleep(0.01) # wait time > 1.08 ms
def set_contrast(self, contrast):
""" Set contrast (0 - 15). """
if contrast < 0:
contrast = 0
if contrast > 0x0f:
contrast = 0x0f
self.write_instruction(0x39)
self.write_instruction(0x70 + contrast)
def set_cursor(self, x, y):
""" set cursor location (address counter)."""
if x < 0: x = 0
if y < 0: y = 0
ddram_addr = y * 0x40 + x
self.write_instruction(0x80 + ddram_addr) # set DDRAM address
def set_entry_mode(self, increment, shift):
mode = 0x04
if (increment): mode = mode + 2
if (shift): mode = mode + 1
self.write_instruction(mode)
def print(self, str, wait = 0):
for c in str:
self.write_data(ord(c))
if (wait > 0): time.sleep(wait)
if __name__ == '__main__':
lcd = St7032iLCD(I2C_ADDR)
# show characters in 2 lines
lcd.set_cursor(0, 0)
lcd.print('1234')
lcd.set_cursor(4, 1)
lcd.print('5678')
# LCD clear
time.sleep(2)
lcd.clear()
# ticker
lcd.set_entry_mode(True, True)
lcd.set_cursor(8, 0)
lcd.print('Hello, this is a ticker message.', 0.5)