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Troubleshooting Modem and Data Communications Problems

Troubleshooting Modem and Data Communications Problems

Although trying to get a new modem to work can be frustrating, you should be able to get your modem up and running by following this step-by-step procedure.

By Robert Causey

After spending some time in the HPHand forum on CompuServe, I noticed that many people had questions related to modems, and data communications in general. Solving modem problems can be frustrating, but it doesn't have to be.

Troubleshooting data communications can be difficult, in part because there are several hardware and software components involved, and determining where the problem resides can be challenging. Fortunately there is an easy process you can follow that can resolve most modem and data communications issues. I thought it might be helpful to review some of the basics and provide a simple modem troubleshooting guide.

 The Basics

 Before you can troubleshoot data communications, it is helpful to have an understanding of the process involved, and some of the key components.

 The beginning of any data communication starts at the communications program, or application, as it is sometimes called. Some examples of these programs are the DataComm and cc:Mail applications built into the 100/200LX.

 First the application will attempt to initialize the modem. The purpose of this process is to prepare the modem for communications and tell the modem how to communicate with other modems and the application.

 The application will attempt to initialize the modem by sending an initialization string, or setup string as it is better known. The setup string consists of a series of commands that set various options in the modem. I will cover this in more detail in a moment. The application will then wait for the modem to signal that it is ready. If all goes well the modem will indicate an OK status and the application will continue.

 The application will then instruct the modem to dial a phone number, either one preconfigured, or one the application had prompted you to enter.

 The modem will connect to the telephone line and dial the phone number it was given. The modem will then wait for another modem at the phone number that was dialed to answer. Ill refer to this second modem as the Host modem.

 Assuming all went well, the modem at the Host answers. The two modems will now start a negotiation process to agree on the speed of the connection and the error handling strategy. This process is often referred to as the handshake. This process normally takes a couple of seconds, and if you have a modem with a speaker, you will hear the high-pitched squeaky tones during this time.

 If all goes well, the two modems agree on the speed of the connection and the error handling strategy. If you have a modem with a speaker, it will go silent at this point.

 The modem tells the application of the success of the connection. Depending on the application, you may sometimes see a message on your screen indicating the connection success.

 At the same time, the modem at the Host notifies its respective application (the Host application) of the incoming call and connection.

 Now that the physical path is established, the applications (palmtop and host) will start to communicate.

 What happens next is determined solely by the two applications, and will vary from application to application. Since a majority of data communications problems occur before this point, I will focus on troubleshooting those areas.


Here is a troubleshooting technique that should help you isolate your problem. First we will prepare the modem and palmtop for the test.

1. For PCMCIA modems, start with your modem card inserted into the palmtop and connected to the phone line. Also, make sure the palmtop has a fresh set of batteries, or is connected to the AC adapter.

For external modems, start with your modem connected to the palmtop, connected to the phone line, and powered on. Also make sure the palmtop and modem have a fresh set of batteries, or are connected to the AC adapter.

 In addition to HPs HP F1015A serial cable, you may also need HPs HP 5181-6642 modem adapter. You could also use a null-modem instead of the modem adapter.

2. Open DataComm by pressing (CTRL)+(QUICKEN). [On the 100LX, press (CTRL)+(cc:MAIL).]

3. Press (MENU) Connect Settings and adjust your settings as follows:

 Baud: 2400

Interface: com2 for PCMCIA modems, com1 for external modems. Parity: Even

Data Bits: 7

Stop Bits: 1

 Then save settings by pressing F10.

4. You should now be at the main terminal screen. We are now ready to begin the test.

5. The rest of the test involves typing the commands directly to the modem. Do not use the connect or dial features of DataComm for this test. The reason is the connect function causes the DataComm program to communicate with the modem on autopilot during dialing. You will need to see the modem results so we will bypass the autopilot.

6. Earlier I mentioned the setup string as being a series of commands. These commands are used to program, or configure, the modem. The AT command is used to get the modems attention. By prefixing it to whatever command you are testing, the modem will recognize the command; otherwise the command may be ignored.

 Type AT and press (ENTER). You should get an ok prompt or 0 prompt. If you do not, your palmtop is not communicating with the modem.

Things to check if there is no response PCMCIA modems

 a) Is the modem card seated well?

b) The connection settings are not as above (see point 3).

c) Modem is configured strangely. Try entering +++ (do not press ENTER).

Also try typing ATZ and hitting (ENTER). When you get an OK prompt, go to the next step.

 Things to check if there is no response : external modems

 a) Is the modem plugged in to the palmtop and turned on?

b) The connection settings are not as above (see point 3).

c) The modem is configured strangely. Try entering +++ (do not press ENTER). Also try ATZ (ENTER).

d) You have not used the correct modem adapter. See point number 1. When you get an OK prompt, go to the next step. If you can not get an OK response, you may have a problem with your modem, cables, or on rare occasions, your palmtop. The best source of help would be the modem manufacturer, or the HPHand forum on CompuServe.

7. Manually enter your modem setup string (get it from the modems manual or the application). Make sure you put the AT in front of the string. For example: ATV1&C3&D2(ENTER)

8. You should get either an OK or 0 response, depending on the contents of the string.

9. If you get an error response, try entering each item individually. For example, using the above string, try typing:


 You will need to refer to your modem manual for the specifics of each command. You should get an OK or 0 response to each command. If you get an error, check the format of the command against the modems manual. Also, note that some modems are case sensitive.

10. If all goes well, place a call to a BBS manually by entering ATDT, followed by the phone number. For example, ATDT555-1212(ENTER). If all goes well, you should get connected without error. You will know you are connected when you see something like CONNECT xxxx yyyy. You will usually see the word connect, followed by a number and other verbiage. The number is the speed the modems are communicating at, and the verbiage will describe the error handling strategy the modems are using (if any).

 If you get a no dial tone or no dial tone message, this indicates a problem with the phone connection. Check the phone cord between the modem and the wall jack. Is this a working jack? To find out, plug into the jack a telephone that you know works. But even if the jack works with a phone, you may have a digital connection, not the analog connection that is required for a modem. Many businesses use fancy telephone systems. These systems typically support two kinds of connections: the digital connections used for the fancy business phones, and the analog connections used for modems and fax machines. Digital connections will not work with modems, and may actually damage them.

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