How to parse multiline response of 09 04 PID from OBD adapter in Android

Question

I am getting raw data from OBD adapter, It is getting parsed for single line but for multiline response I am not able to parse. I used below code to parse

    String hexaData = getResult(); // getResult is here the raw data("4904014A4D422A490402333637364904033135303049040400000000") after parsing I am getting parsed value(JMB*36761500) which is correct and only working for single line 
        Log.i("CalID_hexa", hexaData);
        final String result = getResult();
        String workingData;
        if (result.contains(":")) {//CAN(ISO-15765) protocol.
            workingData = result.replaceAll(".:", "").substring(9);//9 is xxx49040701, xxx is bytes of information to follow.
            Matcher m = Pattern.compile("[^a-z0-9 ]", Pattern.CASE_INSENSITIVE).matcher(convertHexToString(workingData));
            if(m.find()) workingData = result.replaceAll("0:49", "").replaceAll(".:", "");
        } else {//ISO9141-2, KWP2000 Fast and KWP2000 5Kbps (ISO15031) protocols.
            workingData = result.replaceAll("49040.", "");
        }
         calId = convertHexToString(workingData).replaceAll("[\u0000-\u001f]", "");
        L.stringStringHashMap.put("CAL_ID",calId);


public String convertHexToString(String hex) {
        StringBuilder sb = new StringBuilder();
        //49204c6f7665204a617661 split into two characters 49, 20, 4c...
        for (int i = 0; i < hex.length() - 1; i += 2) {

            //grab the hex in pairs
            String output = hex.substring(i, (i + 2));
            //convert hex to decimal
            int decimal = Integer.parseInt(output, 16);
            //convert the decimal to character
            sb.append((char) decimal);
        }
        return sb.toString();
    }

How to parse multiline response like below response on PID 09 04 from OBD Adapter:

18 DA F1 11 10 13 49 04 01 33 37 38 
18 DA F1 1D 10 13 49 04 01 33 37 38
18 DA F1 11 21 30 35 2D 52 59 45 2D
18 DA F1 11 22 41 37 34 30 00 00 55
18 DA F1 1D 21 30 36 2D 52 59 45 2D
18 DA F1 1D 22 41 37 37 30 00 00 55

How can I parse the above?

score 0 · Answer 1 · answered Feb 08 '22 at 17:47

If you want to parse multiple line responses as single line responses then you can first form the array from the multiple line response separating the lines by character \n. After forming the array of responses, you can join the strings in one single line.

score 0 · Answer 2 · answered Feb 15 '22 at 20:04

You have two issues here. The first is that you sent your request using a broadcast address, that's why two ECUs (namely, 18 DA F1 11 and 18 DA F1 1D) answered to your request. You either have to sort these out or ask only one ECU directly.

The second is you should learn about ISO 15765-2 (also named ISO-TP), which is a transport protocol, much like TCP (or rather IP) is for Ethernet. https://en.wikipedia.org/wiki/ISO_15765-2 contains a rough outline.

A general notice: If you're serious about implementing OBD2 communication, write a layered architecture, in which the communication layer (BLE, TTY, TCP, etc.) sits below the vehicle protocol which ISO-TP sits on top of. On the actual application layer you can then decode the individual PIDs and their measurements.

How to parse multiline response of 09 04 PID from OBD adapter in Android

2 Answers2