Android plc通信

终于有时间总结一下用到的技术了，之前忙得狗血淋头，搞这个plc弄到自闭，由于没有百度到任何案例，遂自己花大量的精力给弄出来并应用到运营项目中，给予各位参考

modbus协议封装

modbus是一种通讯规约，简单的来说，由起始符、帧头、寄存器命令、LRC校验、结束符等组成，此文中，modbus主要用于和信捷plc通讯，采用ascll编码方式（RTU类似，自行修改代码中转码部分即可），另外，因为是规约，所以得需要与你的上位机PLC一起对接，例如本文中规约为：寄存器地址长度为4-“0001”,通讯命令长度为1-“1”,意味着，像寄存器0001发送数据1，来完成对应的操作。
modbus封装类：

public class PlcModBusUtil {
   
   
    //起始符
    private final String START = "3A";
    //帧头
    private final String FRAME_HEADER = "3032";
    //写多个寄存器命令
    private final String WRITE_COMMAND = "3130";
    //写单个寄存器
    private final String WRITE_SIGNLE_COMMAND = "3036";
    //读命令
    private final String READ_COMMAND = "3033";
    //结束符
    private final String END = "0D0A";

    public static final String TAG = "PlcModBusUtil";

    /**
     * 封装modbus，写请求协议
     *
     * @return
     */
    public String getWriteString(String address, String[] data) {
   
   
        StringBuilder stringBuilder = new StringBuilder();
        //起始符
        stringBuilder.append(START);
        //帧头
        stringBuilder.append(FRAME_HEADER);
        //功能码
        if (data.length > 1) {
   
   
            stringBuilder.append(WRITE_COMMAND);
        } else {
   
   
            stringBuilder.append(WRITE_SIGNLE_COMMAND);
        }


        //地址,多个地址，只传起始地址，16进制转ascii
        stringBuilder.append(hexToAscii(address));

        //多个地址与数据，需要添加长度和位数
        if (data.length>1){
   
   
            //长度,例如：写2条数据，长度为2，位数为4，长度补足4位，位数补足2位
            StringBuilder lengthBuilder = new StringBuilder();
            lengthBuilder.append(data.length);
            int length = lengthBuilder.length();
            for (int i = 0; i < 4 - length; i++) {
   
   
                lengthBuilder.insert(0, "0");
            }
            //转ascii
            stringBuilder.append(hexToAscii(lengthBuilder.toString()));

            //位数
            StringBuilder digitsBuilder = new StringBuilder();
            digitsBuilder.append(data.length * 2);
            int digitsLength = digitsBuilder.length();
            for (int i = 0; i < 2 - digitsLength; i++) {
   
   
                digitsBuilder.insert(0, "0");
            }
            //转ascii
            stringBuilder.append(hexToAscii(digitsBuilder.toString()));
        }

        //写入数据处理
        for (String datum : data) {
   
   
            //10进制转16进制
            StringBuilder hexString = new StringBuilder();
            hexString.append(datum);
            int hexLength = hexString.length();
            //转化后的16进制进行补位，目标为4位
            for (int i = 0; i < 4 - hexLength; i++) {
   
   
                hexString.insert(0, "0");
            }
            //转ascii，添加数据
            stringBuilder.append(hexToAscii(hexString.toString()));
        }

        //LRC校验结果生成，去掉起始
        stringBuilder.append(getLrc(stringBuilder.substring(START.length())));
        //添加结束符
        stringBuilder.append(END);
        return stringBuilder.toString();
    }

    public String getReadString(String[] address) {
   
   
        StringBuilder stringBuilder = new StringBuilder();
        //起始符
        stringBuilder.append(START);
        //帧头
        stringBuilder.append(FRAME_HEADER);
        //读命令
        stringBuilder.append(READ_COMMAND);
        //地址，多个地址，只传起始地址,16进制转ascii
        stringBuilder.append(hexToAscii(address[0]));

        //长度,例如：写读条数据，长度为2,长度补足4位   位数为4，位数补足2位
        StringBuilder lengthBuilder = new StringBuilder();
        lengthBuilder.append(address.length);
        int length = lengthBuilder.length();
        for (int i = 0; i < 4 - length; i++) {
   
   
            lengthBuilder.insert(0, "0");
        }
        //转ascii
        stringBuilder.append(hexToAscii(lengthBuilder.toString()));

        //LRC校验结果生成，去掉起始
        stringBuilder.append