OT: Cellular modems (1xRTT/CDMA2000)

[newguy]

I'm just getting started on a revamp of a product I developed some time ago. I want to add a remote monitoring/configuration ability. The kinds of features I'd like to add are:

- Remote notification. For instance, it would be nice if the remote unit could send an email to a central monitoring facility or a text message to a cell phone in response to an alarm condition/whatever.
- Remote configuration. It would be really nice if a central monitoring facility could send a coded email/sms message to the unit to set trip points, turn it on/off, request status information, etc.

I've been digging around and, to my untrained eyes, it looks like incorporating these features will be very simple. It seems you just need a cellular modem. Sending emails/SMS are easily done using simple AT commands, and receiving emails/SMS look just as easy.

My question boils down to: is it really this easy? I don't need to incorporate a web server or anything like that, do I?

Lastly, has anyone done something like this before? Any 'gotchas' to look out for?

And the cellular modem is my only option - I can't remotely monitor these things any other way.

[Foppie]

I replied in this thread to such a topic.
I did (quikly) seek but not find any AT commands to send e-mail, so I'm not sure if that is possible...
But sending SMS is really easy, and receiving SMS needs just a little more thought. It's nothing to worry about.

Difficulties might be:
- writing the interrupt
- managing the incoming strings: Expect lots of characters, in my case it wouldn't fit in the RAM.

[newguy]

Thanks Foppie.

I read your comment about running out of RAM, and I was going to ask if you were using a 18F PIC, but I read in the other thread that you're using a 16F.

I don't know if "email" is a proper term.....I know that those modems have the capability of sending a SMS to any email address. That's what I meant. You're right about the protocol, though: it will be a little tricky to properly interface to the modem and send/receive SMS, but nothing I can't handle.

Incidentally, the modem I was looking at is found here: http://www.arcelect.com/CDS_9060_manaul.pdf. Look at the bottom of page 21, and it describes the procedure for sending and receiving SMS. Is it similar to the protocol you're familiar with?

[Foppie]

The modem I am using has two sms modes. PDU and Text. In Text mode the protocol is the same as yours, only in the AT-manual it states <data-address> and it doesn't mention e-mail. It does mention data-address as: "GSM 03.40 TP-Destination-Address Value in string format"

Sending won't be a problem because you don't need your RAM for sending, receiving might be, because you might receive a SMS that is bigger than your largest array of characters. That's what I meant by the RAM problem in this case. You won't run out of RAM (I don't on a PIC16F) but you might have to store it in multiple arrays, which gives overhead.
You will have to think about how to handle that problem...

[newguy]