GSM TextMode special characters

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Michael Debus - 04 Nov 2005 14:57 GMT

Hi,
I try to send sms via GSM-Modem TC35i in text-mode (not pdu-mode). The modem
supports only the GSM alphabet as specified by GSM 03.38.
I have problems to send special signs like "{" or "\". I followed the
specifiction an send i.e. for "{" the characters 0x1b and 0x28 but this
dosnt work.
Any ideas ?

Thanks Michael

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John Henderson - 04 Nov 2005 21:03 GMT

> I try to send sms via GSM-Modem TC35i in text-mode (not
> pdu-mode). The modem supports only the GSM alphabet as
> specified by GSM 03.38. I have problems to send special signs
> like "{" or "\". I followed the specifiction an send i.e. for
> "{" the characters 0x1b and 0x28 but this dosnt work.
> Any ideas ?

When entering text in text-mode, you can't use that mechanism
to get to the extension table. From GSM 07.05, 0x1B has a
higher priority meaning in the context of an "AT+CMGS" or
"AT+CMGW" command, namely "abort the command".

I think you might have exposed the limits of text-mode. My
Wavecom modem just drops characters from the extension table if
I include them (as ordinary ASCII characters) in a message
entered via text-mode.

John

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John Henderson - 05 Nov 2005 00:59 GMT

Earlier, I wrote:

> I think you might have exposed the limits of text-mode.

But I've got more tenacity than that :)

I've found a work-around on my Wavecom 1206b modem. I managed
to send (and read) a message with "\{}" characters by using
8-bit SMS. I typed them directly at the ">" prompt from the
"AT+CMGS" command.

Using 8-bit messaging has two drawbacks: you're limited to 140
characters in a single SMS, and you're dependant on the
receiving device being able to decode and represent 8-bit data
at the man-machine-interface. I think that most can, but I'm
not sure.

Use the "AT+CSMP" command to put the modem into 8-bit mode
before entering your text. Try

AT+CSMP=17,,0,4

The second (missing) parameter is the Validity Period (the time
the SMSC will keep trying to deliver an undeliverable SMS). If
you need to put in a value, 173 means one week IIRC.

I have a TC35 manual (but not a modem), and it suggests that the
above should work. Sending the Euro currency symbol would be a
different matter however. Whilst it's a 7-bit GSM character
from the extension set, it's not an 8-bit ASCII character.

John

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