One weird bug on the XT75

May 30, 2009 — Florent Clairambault

You might have faced this error with your X765 chip. The program crashes with this error :

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^EXIT 00010000,02d6414253485f4c434c2c70726f6365647572655265636f72645f702d3e6e756d6265724f66526567697374657265645461736b73203c3d204d41585f4e4f5f524547495354455245445f5441534b53
 
^SHUTDOWN

If you convert the hex array to some text, that will give you :

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#ABSH_LCL,procedureRecord_p->numberOfRegisteredTasks <= MAX_NO_REGISTERED_TASKS

Which might mean something to someone. But the point is, you won’t find any help. Mostly because it’s an uncommon error.

The error comes from the GPRS connection management. I had it when I was using a wrong APN (with the “AT^SJNET” command) to connect to a host. In my program, connection failed with a classic IOException (“Profile not found”) but 1 or 2 minutes later, the chip was ALWAYS crashed (with the “^EXIT” URC). So, the only solution I found to correct this problem was to automatically detect which APN is required.

This might also improve the ease of deployment of your programs. I like putting as much as possible auto-detection / auto-configuration code as possible. It takes a little time to write it but saves a lot of troubles (last minute configuration, human errors, human explanations, etc.).

The APN auto-detection code is like that :

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public static String AutoDetectApn( ATCommand atc ) {
 
    String[] apnList = {
        "\"gprs\",\"objcobytel.com\",\"\",\"\",\"88.191.11.20\",0", // Bouygues Telecom : "Objet communiquant" / "ObjetCo" / "ObjCo"
        "\"gprs\",\"m2minternet\",\"\",\"\",\"88.191.11.20\",0",
        "\"gprs\",\"internet-entreprise\",\"orange\",\"orange\",\"88.191.11.20\",0",
        "\"gprs\",\"a2bouygtel.com\",\"\",\"\",\"88.191.11.20\",0",
        "\"gprs\",\"b2bouygtel.com\",\"\",\"\",\"88.191.11.20\",0",
        "\"gprs\",\"ebouygtel.com\",\"\",\"\",\"88.191.11.20\",0",
        "\"gprs\",\"movistar.es\",\"movistar\",\"movistar\",\"88.191.11.20\",0",
        "\"gprs\",\"orange\",\"orange\",\"orange\",\"88.191.11.20\",0",
        "\"gprs\",\"orange.fr\",\"orange\",\"orange\",\"88.191.11.20\",0",
        "\"gprs\",\"websfr\",\"\",\"\",\"88.191.11.20\",0"
    };
 
 
   synchronized (atc) {
        System.out.println( "Waiting 30s..." );
        try {
            Thread.sleep( 30000 );
        } catch (InterruptedException ex) {
            ex.printStackTrace();
        }
 
        for (int i = 0; i < apnList.length; ++i) {
            try {
                String apn = apnList[i];
                System.out.println( "Trying apn " + apn + "..." );
                atc.send( "AT^SJNET=" + apn + "\r" );
 
                SocketConnection conn = (SocketConnection) Connector.open( "socket://88.191.11.20:80" );
                conn.close();
                return apn;
            } catch (Exception ex) {
                System.out.println( "Failed : " + ex.getClass() + " : " + ex.getMessage() );
            }
        }
    }
 
 
    // We couldn't find any APN
    return null;
 
}

And it is only launched when the SIM Card has been changed. To detect that, I have some simple code like this :

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{ // APN auto-detection
 
    String imsi;
 
    synchronized (atc) {
         imsi = Common.getIMSI( atc );
    }
 
    if (settings.confLastImsi.compareTo( imsi ) != 0) {
        System.out.println( "Sim card changed ! Auto-detecting APN..." );
 
        synchronized (atc) {
            String apn = Common.AutoDetectApn( atc );
 
            if (apn != null)
                reg.confAPN = apn;
        }
 
        settings.confLastImsi = imsi;
 
        // Whatever happens, we still need to save the current IMSI
        settings.Save();
    }
}

Reference :
- The forum that helped me solve this problem
- Translating Hex to Text

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