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Cellular Radio Module - SIM900 Characters


Hi guys,

I’m working with Cellular Radio Module and trying to send SMS to my cell phone I noticed that something goes wrong when I try to send a message string that contains special characters like the VB constant “vbNewLine”, italian chars like èéàòùì, single quotes, double quotes …

What can I do for avoid this problem?
Where I can find a characters table of SIM900?

Thanks in advance



By “Something goes wrong” what exactly do you mean? Are chars missing from the end of the string? Does it not send at all? Does it replace those with chars with something else?


SMS for normal text is limited to 127 bit so accented or characters over 127 don’t work. See here.

The way they send the likes of Chinese etc is through 2 byte encoding and you are then limited to 70 characters per message.

If you are using the standard AT+CMGF=1 for text mode, you will be limited. To use anything else you’ll need use PDU mode.


Hi, thanks to both for reply.

@ Dave McLaughlin - I’ll read the link, thank you!

@ James - “Something goes wrong” means that, for example, if I try to send a message that includes the % character the SMS received from my smartphone ends before the % char. If I remove the % character from the message my smartphone receive correctly all the message I sent.