NerdKits - electronics education for a digital generation

You are not logged in. [log in]

NEW: Learning electronics? Ask your questions on the new Electronics Questions & Answers site hosted by CircuitLab.

Microcontroller Programming » Connection to cell phones

September 21, 2009
by prasaday1
prasaday1's Avatar

Can I program nerdkit to dial phone numbers based on the certain response from temperature sensor.

Thanks,

PA

September 21, 2009
by wayward
wayward's Avatar

I suppose that depends on how you interface to the cell phone. I know that some of them do support the extended Hayes set of commands, once used to talk to phone-line modems. But your problem of immediate concern is the actual wiring and protocol you would use to talk to the phone in the first place. If you really must use the phone/SIM card to dial out, then I think you'd best look around on the manufacturer's website, or ask on specialized cellphone forums about hooking up your phone to the computer (or, alternatively, directly to the NerdKit, but that could be more trouble than it's worth for 99% of the phones out there).

Alternatively, you can take a look at Skype development tools and API. If it's all the same to you whether you dial out using your cell phone or Skype, then this may be the easiest way out.

Cheers,

Zoran

September 22, 2009
by rusirius
rusirius's Avatar

The other "quick and dirty" way to do it would be to just tie into the buttons you needed...

i.e. if you were dialing 410-541-9155, then you only need the 0,1,4,5,9 and SEND keys... See if the buttons are pulling up or down, and then just do it with the MCU instead... Then you can just "press 4", delay, "release 4", delay, "press 1" delay, "release 1", delay, etc.... Finally "push" the send key and make the call...

If you need a "voice" on the call, you can wire the mic input up with one of those "voice recorder" chips to play out a message... Of course you might also want to do some sampling of the speaker output to determine when somebody "answers"... All in all it should be a pretty fun project to play around with... For a cheap way of doing it, just buy one of the pre-paid cell phones and rip it apart... ;)

September 22, 2009
by maas15
maas15's Avatar

If voice isn't needed, have you considered using an external modem? They're really easy to deal with, and your nerdkit already has a serial connection. It's usually a short string to set up the modem (which is sorta optional, it sets up hangup options, dialing speed, etc), and then something like "ATDT5551212" to call someone, and "++ATH" to hang up.

Though, as a disclaimer, I should add that I haven't actually tried to use my serial port in any projects yet

September 22, 2009
by maas15
maas15's Avatar

Whoops, I was intending to include the following link to modem commands.

http://docs.kde.org/development/en/kdenetwork/kppp/appendix-hayes-commands.html#hayes-basic-commands

September 22, 2009
by tech20
tech20's Avatar

I would use the "cheap and dirty" way of doing it. Measure the hold time of the button for one digit, wire up the keys to the ATmega168 C pins(basic IO, I'm not familiar with voltages in cell phones, so you may need to lower the 5v used) and use ms_delay(t); to set the "button press" timing.

September 22, 2009
by rusirius
rusirius's Avatar

The other "cheap trick" when dealing with things like that is to throw the emitter and collector over the "contacts" and then drive the base... (make sure the polarity is right for the type of transistor you use...)

Post a Reply

Please log in to post a reply.

Did you know that a piezoelectric buzzer can be used in reverse as a microphone? Learn more...