用LCD1602显示树莓派的运行情况

在树莓派上有很多方式能够了解系统的运行情况，例如我们常用的top和htop命令，但是这些方法都需要使用终端才能看到系统运行的情况，有些时候显得不是很方便。接下来我介绍一种使用LCD1602显示树莓派运行情况的方法。

材料

• 树莓派一个
• II2接口LCD1602
• 面包板
• 公对母以及公对公杜邦线若干

接线

代码

# import lib
import I2C_LCD_driver
from time import sleep, strftime, time
from gpiozero import CPUTemperature, DiskUsage
import Adafruit_DHT
import psutil
import subprocess
import math

# init variables
mylcd = I2C_LCD_driver.lcd()
cpu = CPUTemperature(min_temp=20, max_temp=100)
cpuTempCurr = 0
cpuUsageCurr = 0
disk = 0
ram = 0
i = 0
symbol = ''
lstUsage = []
displayDuration = 2
symbolsTable = [   
        # arrow up
        [   0x04, 0x0E, 0x1F, 0x00, 0x00, 0x00, 0x00, 0x00],
        # arrow down
        [   0x1F, 0x0E, 0x04, 0x00, 0x00, 0x00, 0x00, 0x00],
        # square
        [   0x0E, 0x0E, 0x0E, 0x00, 0x00, 0x00, 0x00, 0x00],
]

# display a small barchart with goal / max value
def displaySmallBar(row, value):
    for i in range (0, 6):
        if i * 17 > value:
            symbol = '.'
        else:
            symbol = chr(255)

        mylcd.lcd_display_string(symbol, row, i + 9)        

# display the screen for a number of defined seconds
def screenDisplay():
    sleep(displayDuration)
    mylcd.lcd_clear()

# format and display the disk usage value on the first row  
def showDiskUsageMini(disk):
    mylcd.lcd_display_string('DSK: {:.0f}%'.format(disk), 1, 0)
    mylcd.lcd_display_string('[', 1, 8)
    mylcd.lcd_display_string(']', 1, 15)

    displaySmallBar(1, disk)

    screenDisplay()

# format and display the RAM usage value on the second row  
def showRAMUsageMini(ram):
    mylcd.lcd_display_string('RAM: {:.0f}%'.format(ram), 2, 0)
    mylcd.lcd_display_string('[', 2, 8)
    mylcd.lcd_display_string(']', 2, 15)

    displaySmallBar(2, ram)

# from https://github.com/donthideyourfeelings/rpimon
def getCommandOutput(cmd):
    out = subprocess.Popen(cmd,
                           stdout=subprocess.PIPE,
                           stderr=subprocess.STDOUT,
                           shell=True)

    stdout, stderr = out.communicate()

    return stdout.decode('utf-8')

# from https://github.com/donthideyourfeelings/rpimon   
def getUsernameHostname():
    cmd = "whoami"
    cmd2 = "hostname"

    username = getCommandOutput(cmd).replace("\n", "")
    hostname = getCommandOutput(cmd2).replace("\n", "")

    return username + "@" + hostname

# get the kpi variation symbol based on the current value and the previous value. Symbols recorded into the array symbolsTable  
def getSymbolIndex(currVal, prevVal): 
    if currVal > prevVal:
        symbolIndex = 0
    elif currVal < prevVal:
        symbolIndex = 1
    else:
        symbolIndex = 2

    return symbolIndex

# represent the last 16 CPU usage values as a bar chart 
def showCPUChart(cpuUsageCurr):
    bars = [
        # 1 bar
        [ 0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x1F],
        # 2 bars
        [ 0x00,0x00,0x00,0x00,0x00,0x00,0x1F,0x1F],
        # 3 bars
        [ 0x00,0x00,0x00,0x00,0x00,0x1F,0x1F,0x1F],
        # 4 bars
        [ 0x00,0x00,0x00,0x00,0x1F,0x1F,0x1F,0x1F],
        # 5 bars
        [ 0x00,0x00,0x00,0x1F,0x1F,0x1F,0x1F,0x1F],
        # 6 bars
        [ 0x00,0x00,0x1F,0x1F,0x1F,0x1F,0x1F,0x1F],
        # 7 bars
        [ 0x00,0x1F,0x1F,0x1F,0x1F,0x1F,0x1F,0x1F],
        # 8 bars
        [ 0x1F,0x1F,0x1F,0x1F,0x1F,0x1F,0x1F,0x1F],
    ]

    mylcd.lcd_load_custom_chars(bars)
    mylcd.lcd_display_string("CPU Usage: ", 1,0)
    mylcd.lcd_display_string("{:.1f}%".format(cpuUsageCurr), 1,11)

    for j in range (0, len(lstUsage)):
        val = int(math.trunc(lstUsage[j] / 10))
        mylcd.lcd_display_string(chr(val), 2, j)

    screenDisplay()

# display information related to the device 
def showMainInfo():
    mylcd.lcd_display_string(getUsernameHostname(),1, 2)
    mylcd.lcd_display_string(strftime("%d/%m %H:%M"),2, 2)
    screenDisplay()

# format and display the CPU usage and temperature values plus a symbol based on the variation between the current and the previous values
def showCPUInfo(cpuTempCurr, cpuTempPrev, cpuUsageCurr, cpuUsagePrev):
    mylcd.lcd_load_custom_chars(symbolsTable)
    mylcd.lcd_display_string("CPU",1, 6)
    mylcd.lcd_display_string("{:.1f}%".format(cpuUsageCurr),2, 0 if cpuUsageCurr >= 10 else 1)
    mylcd.lcd_display_string("{:04.1f}C".format(cpuTempCurr),2, 9)
    mylcd.lcd_display_string(chr(getSymbolIndex(cpuUsageCurr, cpuUsagePrev)), 2, 5)
    mylcd.lcd_display_string(chr(getSymbolIndex(cpuTempCurr, cpuTempPrev)), 2, 14)
    screenDisplay() 

# main
mylcd.lcd_clear()
if __name__ == '__main__':
    try:
        while True:
            print("-----")

            # get data
            cpuTempPrev = cpuTempCurr
            cpuTempCurr = cpu.temperature
            cpuUsagePrev = cpuUsageCurr
            cpuUsageCurr = psutil.cpu_percent()
            disk = DiskUsage()
            ram = psutil.virtual_memory()[2]

            # data stored to generate the CPU's barchart
            lstUsage.append(cpuUsageCurr)

            # display the screens
            showMainInfo()
            showCPUInfo(cpuTempCurr, cpuTempPrev, cpuUsageCurr, cpuUsagePrev)
            showCPUChart(cpuUsageCurr)
            showRAMUsageMini(ram)   
            showDiskUsageMini(disk.usage)   

            # loop / CPU's barchart reset everything 16 steps (LCD screen size)
            if i > 15:
                i = 0
                del lstUsage [:]
                mylcd.lcd_clear()
            else:
                i = i + 1

    except KeyboardInterrupt:
        print("Off")
        mylcd.lcd_clear()
        mylcd.backlight(0)

显示效果

大功告成！