如何在Java上使用grovepi和pi4jv2？

Question

我最近想在树莓派 3 上使用 pi4j v2 库的 Grove lcd rgb 显示器，操作系统：dietpi。 我遵循了所有 pi4j 文档（https://www.pi4j.com/about/new-in-v2/），我还遵循了 Grove 库的文档（有点过时）（https://dexterind） .github.io/GrovePi/）。尽管我进行了所有尝试，但我无法使用 pi4j 在 i2c 端口上写入。但是，当我启动 jar 时，控制台上没有出现任何错误，并且我的测试脚本告诉我正在写入它。 i2c 端口在 Dietpi 上启用，奇怪的是，我的测试在 python 中运行得很好。 你有遇到过类似的问题吗？

这是我的java示例测试： （注意：GrovePi4j 类是 Grove 库提供的预配置类。i2c 输入/输出是预配置的，与 python 示例中的相同。）

import java.io.IOException;
import java.util.Random;

import com.github.yafna.raspberry.grovepi.GroveDigitalOut;
import com.github.yafna.raspberry.grovepi.GrovePi;
import com.github.yafna.raspberry.grovepi.devices.GroveRgbLcd;
import com.github.yafna.raspberry.grovepi.pi4j.GrovePi4J;
import com.pi4j.Pi4J;
import com.pi4j.context.Context;


public class LcdService {
    
    public void exec() throws IOException, InterruptedException {
        Context pi4j = Pi4J.newAutoContext();
        GrovePi grovePi = new GrovePi4J(pi4j);
        GroveRgbLcd lcd = grovePi.getLCD();

        String[] phrases = new String[]{
          "Hi! ALL!",
          "This should work just fine",
          "A message\nA response",
          "More data that you can handle for sure!",
          "Welcome to the internet of things with java",
          "Short\nMessage"
        };
        int[][] colors = new int[][]{
          {50, 255, 30},
          {15, 88, 245},
          {248, 52, 100},
          {48, 56, 190},
          {178, 25, 180},
          {210, 210, 210}
        };
        while (true) {
          try {
            String text = phrases[new Random().nextInt(phrases.length)];
            int[] color = colors[new Random().nextInt(colors.length)];
            lcd.setRGB(color[0], color[1], color[2]);
            Thread.sleep(100);
            lcd.setText(text);
            Thread.sleep(2000);
          } catch (IOException io) {
          }
        }
    }
}

这是我的Python示例测试：

import time,sys

if sys.platform == 'uwp':
    import winrt_smbus as smbus
    bus = smbus.SMBus(1)
else:
    import smbus
    import RPi.GPIO as GPIO
    rev = GPIO.RPI_REVISION
    if rev == 2 or rev == 3:
        bus = smbus.SMBus(1)
    else:
        bus = smbus.SMBus(0)

# this device has two I2C addresses
DISPLAY_RGB_ADDR = 0x62
DISPLAY_TEXT_ADDR = 0x3e

# set backlight to (R,G,B) (values from 0..255 for each)
def setRGB(r,g,b):
    bus.write_byte_data(DISPLAY_RGB_ADDR,0,0)
    bus.write_byte_data(DISPLAY_RGB_ADDR,1,0)
    bus.write_byte_data(DISPLAY_RGB_ADDR,0x08,0xaa)
    bus.write_byte_data(DISPLAY_RGB_ADDR,4,r)
    bus.write_byte_data(DISPLAY_RGB_ADDR,3,g)
    bus.write_byte_data(DISPLAY_RGB_ADDR,2,b)

# send command to display (no need for external use)
def textCommand(cmd):
    bus.write_byte_data(DISPLAY_TEXT_ADDR,0x80,cmd)

# set display text \n for second line(or auto wrap)
def setText(text):
    textCommand(0x01) # clear display
    time.sleep(.05)
    textCommand(0x08 | 0x04) # display on, no cursor
    textCommand(0x28) # 2 lines
    time.sleep(.05)
    count = 0
    row = 0
    for c in text:
        if c == '\n' or count == 16:
            count = 0
            row += 1
            if row == 2:
                break
            textCommand(0xc0)
            if c == '\n':
                continue
        count += 1
        bus.write_byte_data(DISPLAY_TEXT_ADDR,0x40,ord(c))

#Update the display without erasing the display
def setText_norefresh(text):
    textCommand(0x02) # return home
    time.sleep(.05)
    textCommand(0x08 | 0x04) # display on, no cursor
    textCommand(0x28) # 2 lines
    time.sleep(.05)
    count = 0
    row = 0
    while len(text) < 32: #clears the rest of the screen
        text += ' '
    for c in text:
        if c == '\n' or count == 16:
            count = 0
            row += 1
            if row == 2:
                break
            textCommand(0xc0)
            if c == '\n':
                continue
        count += 1
        bus.write_byte_data(DISPLAY_TEXT_ADDR,0x40,ord(c))

# Create a custom character (from array of row patterns)
def create_char(location, pattern):
    """
    Writes a bit pattern to LCD CGRAM

    Arguments:
    location -- integer, one of 8 slots (0-7)
    pattern -- byte array containing the bit pattern, like as found at
               https://omerk.github.io/lcdchargen/
    """
    location &= 0x07 # Make sure location is 0-7
    textCommand(0x40 | (location << 3))
    bus.write_i2c_block_data(DISPLAY_TEXT_ADDR, 0x40, pattern)

# example code
if __name__=="__main__":
    setText("Hello world\nThis is an LCD test")
    setRGB(0,128,64)
    time.sleep(2)
    for c in range(0,255):
        setText_norefresh("Going to sleep in {}...".format(str(c)))
        setRGB(c,255-c,0)
        time.sleep(0.1)
    setRGB(0,255,0)
    setText("Bye bye, this should wrap onto next line")

Answer 1

使用 Linux i2cdetect 工具确认在 I2C 总线上正确检测到 Grove LCD RGB 显示器

sudo i2cDetect -y 1

地址 0x62 和 0x3E 应该出现（分别是背光和文本的地址）。如果没有，请检查接线和连接。