SMS Length Rulez! (or is it SMS Length Rules?)



I’ve been receiving ERROR 305 when I try to send an SMS message of 550 characters.

I’m currently using the ADL_SMS_MODE_TEXT mode. Do I maybe need to be using ADL_SMS_MODE_PDU? I tried it, but the system seems to lock.

What are the rules regarding SMS Length? I had a quick look on the net, and it seems that 160 chars is the limit for a single SMS. Is this correct?

I have no difficulty sending an SMS of <160 chars (and strangely it also works for 165 chars).

Any help would be well appreciated!



Yes it is - for 7-bit characters:

The underlying “packet” used by the GSM infrastructure is the PDU = Protocol Data Unit.

A PDU can contain 140 octets (8-bit bytes) of payload data;

7-bit text data can be “compressed” such that 160 7-bit characters will fit into the 140 octets of a PDU.
(160x7 bits = 140x8 bits = 1120 bits total).

Hence the maximum size of a text message is 160 characters.

Yes, that is strange! :open_mouth:

What do you mean by “works” - are all 165 characters actually received at the other end?

If you want to send >160 characters, you will have to spit it over multiple messages, or work out some way to compress it into a single message…


Thanks for clearing that up for me, much appeciated!

I’m pretty sure that the SMS would have been truncated for 165 chars, now that I think of it.