modem communication problem

[alexbilo]

Hi,

I try to set up a linux box that sends a message to a pager when an event occurs.

I can use the modem to do just that in minicom (same thing than hyperterminal in windows), but when I want to access the modem in Labview, everything just go wrong. My modem is tied to a VISA device (ASRL5::INSTR) and I access it with an alias (MODEM).

When I send AT commands to the modem, I always miss the first character of the echo :

send string "ATZ\r"

get string "TZ\r\rOK\r"

The modem also behaves erratically, most of the time it doesn't even respond to the AT commands.

Any idea?

Thanks,

Alex

[MichaelChaney]

Hi Alex,

Usually problems like this are a result of impropper message termination.  It looks like you are manually appending a "\r" to your string.  Were you also doing this in minicom?  It looks like you device echos back the command and is showing a "\r\r".  Most modems terminate with a CR LF (carriage return + line feed, the same as the <Enter> key).  If you were using the enter key in minicom to terminate the command, try using "\r\n" to terminate in LabVIEW.

[alexbilo]

Hi Michael,

Thank you for your answer. Unfortunately, the modem's documentation specify that the commands should be terminated by \r, although it can also recognize \r\n. Anyway, I did test this with no results.

The strings above are just an example, in fact the result vary with each request. Sometimes the modem reacts badly (clicking without reason, even freezing the computer).

Thanks,

Alex

Message Edité par AlexTR le 02-19-2006 05:31 PM

[MichaelChaney]

Hi Alex,

It sounds like there might be something wrong with the modem, or something wrong with the line.  The clicking is probably the relay on the modem connecting and disconnecting the line.  This could be caused by no dialtone, busy line, or a damaged modem.  I'm not aware of any strings or commands that could cause a modem to behave like this or to freeze the computer.  I would take a closer look at the modem or the line.