1.点亮屏幕

OLED屏幕指的是这个：

这是块0.96寸的单色屏幕，分辨率是：128*64，芯片型号是SSD1306。

开启它依然需要启用I2C总线并安装smbus库，方法在上一篇文章中可以找到。

使用i2cdetect命令能看到总线地址，其中0x3c就是OLED屏幕的地址。

另外还要安装一个Adafruit_Python_SSD1306的库（之前的例程中已经运行过的就不用再运行了，我也不知道这里面哪些代码是真正有用的，没试，直接全部安装了）：

apt-get update
apt-get upgrade
pip3 install --upgrade setuptools
apt-get install python3-pip
pip3 install RPI.GPIO
pip3 install adafruit-circuitpython-ssd1306
apt-get install python3-pip
apt-get install python3-pil
git clone https://github.com/adafruit/Adafruit_CircuitPython_SSD1306.git 
cd Adafruit_CircuitPython_SSD1306-master
python setup.py install

运行下面的python代码，就可以点亮屏幕了：

import time
import busio
import adafruit_ssd1306
from board import SCL, SDA
from PIL import Image, ImageDraw, ImageFont

OLED_WIDTH  = 128
OLED_HEIGHT = 64

i2c = busio.I2C(SCL, SDA)
oled = adafruit_ssd1306.SSD1306_I2C(OLED_WIDTH, OLED_HEIGHT, i2c)

while True:
    oled.fill(0)

    image = Image.new('1', (oled.width, oled.height))
    draw = ImageDraw.Draw(image)
    font = ImageFont.truetype('/root/board/fonts/Courier_New.ttf', 32)

    draw.text((0, 0),  'Hello', font=font, fill=255)
    draw.text((0, 32),  'World', font=font, fill=255)

    oled.image(image)
    oled.show()

    time.sleep(1)

效果如下（由于相机和屏幕刷新频率问题，拍不全）：

2.展示更多信息

接下来我们就可以用这块屏幕展示一些有用的信息了。

比如，ip地址信息（上面的是wifi地址，下面的是有线网卡地址）：

日期时间信息：

系统统计信息（CPU负载、内存占用、磁盘占用、CPU温度）

环境温湿度信息（温度好像不准，虚高）：

温湿度的传感器是这个（DHT11）：

使用温湿度传感器需要安装额外的库：

git clone https://github.com/adafruit/Adafruit_Python_DHT.git
2. 
cd Adafruit_Python_DHT
python setup.py install
python3 setup.py install

CPU各核心实时频率：

代码如下（各个屏幕滚动展示）：

import sys
import time

import socket
import fcntl
import struct
import board
import busio
import subprocess

import Adafruit_DHT
import adafruit_ssd1306

from board import SCL, SDA
from PIL import Image, ImageDraw, ImageFont

font_cn = ImageFont.truetype('/root/board/fonts/微软雅黑.ttf', 14)
font_en = ImageFont.truetype('/root/board/fonts/Courier_New.ttf', 14)

def get_ip_address(ifname):
    s = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
    return socket.inet_ntoa(fcntl.ioctl(
        s.fileno(),
        0x8915,  # SIOCGIFADDR
        struct.pack('256s', str.encode(ifname[:15]))
    )[20:24])

def show_screen_ip():
    oled.fill(0)
    WIFIADDR = ""
    WIREADDR = ""
    try:
        WIFIADDR += get_ip_address('wlan0')
    except IOError:
        WIFIADDR += "0.0.0.0"
    try:
        WIREADDR += get_ip_address('eth0')
    except IOError:
        WIREADDR += "0.0.0.0"
    image = Image.new('1', (oled.width, oled.height))
    draw = ImageDraw.Draw(image)
    draw.text((0, 10), WIFIADDR, font=font_en, fill=255)
    draw.text((0, 30), WIREADDR, font=font_en, fill=255)
    oled.image(image)
    oled.show()

def show_screen_time():
    oled.fill(0)
    image = Image.new('1', (oled.width, oled.height))
    draw = ImageDraw.Draw(image)
    draw.text((0, 0),  time.strftime("%A"), font=font_en, fill=255)
    draw.text((0, 20), time.strftime("%Y-%m-%d"), font=font_en, fill=255)
    draw.text((0, 40), time.strftime("%X"), font=font_en, fill=255)
    oled.image(image)
    oled.show()

def show_screen_stats():
    oled.fill(0)
    image = Image.new('1', (oled.width, oled.height))
    draw = ImageDraw.Draw(image)

    cmd = "top -bn1 | grep load | awk '{printf \"%.2f\", $(NF-2)}'"
    cpustr = subprocess.check_output(cmd, shell=True).decode("utf-8")
    cmd = "free -m | awk 'NR==2{printf \"%s MB\", $3 }'"
    memstr = subprocess.check_output(cmd, shell=True).decode("utf-8")
    cmd = "df -h | awk '$NF==\"/\"{printf \"%d GB\", $3}'"
    diskstr = subprocess.check_output(cmd, shell=True).decode("utf-8")
    cmd = "expr `cat /sys/class/thermal/thermal_zone0/temp` / 1000"
    tempstr = subprocess.check_output(cmd, shell=True).decode("utf-8")

    draw.text((0, 0),  "CPU: " + cpustr, font=font_en, fill=255)
    draw.text((0, 14), "MEM: " + memstr, font=font_en, fill=255)
    draw.text((0, 28), "DSK: " + diskstr, font=font_en, fill=255)
    draw.text((0, 44), "TMP: " + tempstr, font=font_en, fill=255)

    oled.image(image)
    oled.show()

def show_screen_climate():
    oled.fill(0)
    image = Image.new('1', (oled.width, oled.height))
    draw = ImageDraw.Draw(image)

    humistr, tempstr = Adafruit_DHT.read_retry(Adafruit_DHT.DHT11, 4)

    draw.text((0, 0),  '温度 : {0:0.1f}度'.format(tempstr), font=font_cn, fill=255)
    draw.text((0, 20), '湿度 : {0:0.1f}%'.format(humistr), font=font_cn, fill=255)

    oled.image(image)
    oled.show()

def show_screen_cpufreq():
    oled.fill(0)
    image = Image.new('1', (oled.width, oled.height))
    draw = ImageDraw.Draw(image)

    cmd = "expr `cat /sys/devices/system/cpu/cpu0/cpufreq/scaling_cur_freq` / 1000"
    cpu0str = subprocess.check_output(cmd, shell=True).decode("utf-8")
    cmd = "expr `cat /sys/devices/system/cpu/cpu1/cpufreq/scaling_cur_freq` / 1000"
    cpu1str = subprocess.check_output(cmd, shell=True).decode("utf-8")
    cmd = "expr `cat /sys/devices/system/cpu/cpu2/cpufreq/scaling_cur_freq` / 1000"
    cpu2str = subprocess.check_output(cmd, shell=True).decode("utf-8")
    cmd = "expr `cat /sys/devices/system/cpu/cpu3/cpufreq/scaling_cur_freq` / 1000"
    cpu3str = subprocess.check_output(cmd, shell=True).decode("utf-8")

    draw.text((0, 0),   "CPU0 : " + cpu0str, font=font_en, fill=255)
    draw.text((0, 15),  "CPU1 : " + cpu1str, font=font_en, fill=255)
    draw.text((0, 30),  "CPU2 : " + cpu2str, font=font_en, fill=255)
    draw.text((0, 45),  "CPU3 : " + cpu3str, font=font_en, fill=255)

    oled.image(image)
    oled.show()

i2c = busio.I2C(SCL, SDA)
oled = adafruit_ssd1306.SSD1306_I2C(128, 64, i2c)

while True:
    # ip地址
    show_screen_ip()
    time.sleep(2)
    # 时间
    show_screen_time()
    time.sleep(2)
    # 统计信息
    show_screen_stats()
    time.sleep(2)
    # 环境信息
    show_screen_climate()
    time.sleep(2)
    # CPU频率
    show_screen_cpufreq()
    time.sleep(2)