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Which GSM to send SMS? Newbie question...

 
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rbruinsma

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Joined: 06 Jun 2011
Posts: 7
Location: fryslan

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PostPosted: Sun Jul 10, 2011 8:36 am    Post subject: Which GSM to send SMS? Newbie question... Reply with quote

I want to send a SMS with a ATMEGA8 or 324 microcontroller and a GSM. I have read a lot of this subject on this forum on how to do this and which GSM to use. I have tested this with a Nokia3310 and a Siemens M35 but with no luck.

I ran in serveral problems, PDU, FBUS etc. But I want to keep things simple... Smile

What I want is a simple and cheap GSM to use so I can connect it with my ATMEGA and send in clear text SMS messages with AT Commands.

I have a few questions about this subject:

- Please advice which GSM to buy to accomplish this? (no more than ±20 euro´s on ebay)

- Do I need to use an external oscillator or can I use the internal oscillator of the ATMEGA to send the AT commands to the GSM?

- Which pins do I need to use to connect the GSM to the ATMEGA? Now I only use one pin: from GSM Rx to ATMEGA Tx. Is that correct or do I need to connect more pins?

All help and answers are welcome, thanks!
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albertsm

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Joined: 09 Apr 2004
Posts: 4966
Location: Holland

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PostPosted: Sun Jul 10, 2011 9:51 pm    Post subject: Re: Which GSM to send SMS? Newbie question... Reply with quote

rbruinsma wrote:
I want to send a SMS with a ATMEGA8 or 324 microcontroller and a GSM. I have read a lot of this subject on this forum on how to do this and which GSM to use. I have tested this with a Nokia3310 and a Siemens M35 but with no luck.

I ran in serveral problems, PDU, FBUS etc. But I want to keep things simple... Smile

What I want is a simple and cheap GSM to use so I can connect it with my ATMEGA and send in clear text SMS messages with AT Commands.

I have a few questions about this subject:

- Please advice which GSM to buy to accomplish this? (no more than ±20 euro´s on ebay)

- Do I need to use an external oscillator or can I use the internal oscillator of the ATMEGA to send the AT commands to the GSM?

- Which pins do I need to use to connect the GSM to the ATMEGA? Now I only use one pin: from GSM Rx to ATMEGA Tx. Is that correct or do I need to connect more pins?

All help and answers are welcome, thanks!


- use a m324P or any other micro that has 2 UARTS. you need one uart for the gsm, the orther for debug
- you can best use a gsm modem like SIMCON 300 (has a connected which is easy to solder) or a SIMCON 900 (newer but SMD). you could also use a BT module if you use a mobi with BT module. Or use an old mobi which can be controlled by RS-232. All depends if you need just one, or more.
- for low baud rate you can use th einternal osc, but i would recommend using a crystal.
- you need to connect TX of mega to the RX of the modem. you must take care of the voltage. Most modems accept not more then 2.8V
- connect RX of mega to TX of the modem.
if using a phone with interface, maybe all you need is a max232 level converter. it all depends on the phone then.
- first send some AT commands :
print "AT"
and see if you get an OK back.

check out the recon project from the AN.

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rbruinsma

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Joined: 06 Jun 2011
Posts: 7
Location: fryslan

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PostPosted: Mon Jul 11, 2011 7:29 am    Post subject: Reply with quote

Thanks Mark! A lot of useful information.
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bzijlstra

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Joined: 30 Dec 2004
Posts: 1179
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PostPosted: Tue Jul 12, 2011 8:00 pm    Post subject: cheap... Reply with quote

http://finch.am/projects/arduinogsm/
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