View Full Version : Questions about a phone project.

08-06-2005, 06:56 PM

I'm new to the forums here and also new to BS2.·I have some questions·for you BS2 gurus here.

I'm currently working on building a land line phone that is capable of collecting and storing·Contacts (phone numbers and info)·from handphones via several means (such as InfraRed, USB, Bluetooth) with the BS2p40.

I was wondering if there's anyone here who did projects that is similar to one such as mine, because I really need guidance. I read that, in order to communicate with handphones, I would require different protocols (1 for IR, 1 for Bluetooth, and maybe 1 for USB?). Can someone tell me of the various different protocols?

In addition to that, I was wondering if the BS2p40 is capable of handling all these 3 functions on top of the basic dialing circuitry, memory storage EEPROM?


Paul Baker
08-06-2005, 08:14 PM
Ok Im a little confused about your request, you desire to collect and store contact information.
How is this information collected, are you capturing the DTMF (phone key presses) or are you capturing Caller ID information, or both?
Second for what purpose does the IR/Bluetooth/USB connection serve? Is it to sync the contact information with another device (PDA/cellphone/computer)?

As a preliminary answer to part of your question, the BS2 has a DTMFOUT function which can be used to dial a number, refer to pages 167-170 of the Basic Stamp Manual (http://www.parallax.com/dl/docs/prod/stamps/BasicStampMan.pdf#page=171). The pages also give an example interface circuit so you can safely interface your stamp with the phone line. The downside is there is no DTMFIN, nor is there any easy means for capturing CallerID information directly. The BS2 simply doesn't run fast enough to do either of these functions. To do either of these using the BS2, you will have to add an external chip capable of performing either/both of these operations.

Now if you collect your contact information only through syncing with an external device (not through DTMF or Caller ID) you could quite possibly be able to do most if not all the functions through the BS2 with minimal external components.

You state you are new to the world of BS2, is this your first development platform or do you have experience working with other chips? The reason I ask is; this is not a beginner project, at best it is an intermeadiate level project, approaching an advanced level. You should work through all the example experiements which came with your BS2 in addition to studying What's a Microcontroller (http://www.parallax.com/dl/docs/books/edu/Wamv2_2.pdf), this will give you some experience that will be nessesary before attempting more advaced projects such as this. Failing to do so will make the project significantly more difficult (therefore you're much less likely to end up with a working system), and also you run the definite risk of destroying your BS2. For instance, If you tried to connect your BS2 directly to the phone line you will end up with an expensive paperweight that doesn't even work well as a paperweight.


Post Edited (Paul Baker) : 8/6/2005 1:20:13 PM GMT

Bruce Bates
08-06-2005, 08:52 PM
Gabe -

When you say "handphones" do you mean handheld cell phones?


Bruce Bates

08-06-2005, 08:58 PM
Hi Paul and Bruce,

Thanks for the reply. I'm sorry for not specifying clear enough what my queries was.

To Bruce, yes I meant handheld cell phones.

To Paul,

I'm actually a student working on a project done by a previous group of students. They have constructed a land line telephone with a BS2p40 as its 'main brain'. It has a 4x4 matrix keypad for keying numbers and alphabets (for functions such as dialing directly from the device / storing contacts in a seperate EEPROM that is in the circuitry of the device). There is also a 4x20 LCD for display. Basically, the device could dial out a number like a normal land line telephone, and storing contacts by keypad input.

Now, my group and I are going to try and improve on the device, by adding additional ways to storing contacts in the device, and thats where the IR, USB, Bluetooth comes in. (e.g. The device has a IR (or USB/Bluetooth) port that is able to detect a handphone (or a PC in the case of USB), and is able to communicate with the handphone/PC to retreive contact information from it and store it directly into the EEPROM in the device.

Ideally, I would like the device to be able to send contact information to a handphone too (just in case, loss of handphone or new SIM card being inserted into the phone.), but this can wait. I would prefer the device to be able to take in contact information before I get started on the sending part.

With regards to your questions, I must say my group and I have very little development experience prior to this. I have worked with microcontrollers such as motorola 68HC11 in school, and did very basic programming on C. We chose the project because we felt that it was rather challenging, we thought we would learn as we go along, but so far it seems to me we have too much questions regarding various concepts to get ourselves up and going.

Please pardon my limited english, I'm actually from Singapore =)


Paul Baker
08-06-2005, 09:43 PM
Your english is exceptional considering it is a second language for you.

The project seems much more "do-able" now that you have clarified the scope of your project.

I have a feeling that the USB interface will be the easiest to do, adding a product such as Parallax's USB2SER device should take care of the hardware aspect of the BS2 communicating with a PC via USB. I have not implemented this myself, but other members most likely have, and they would be able to give more specific advice on the software required to inteface with the USB2SER.

The IR and bluetooth will likely be more problematic, because not only will you need to be concerned about the hardware interface, you will have to implement the communication protocol that your handphone expects. And unfortunately there isn't a standard protocol that all devices use. You will likely have to find out the specific protocol for whatever handphone you will be using.

Bluetooth has a standard protocol, but unfortuantely some manufacturers do not completely follow the protocol, with luck your handphone will. Using Parallax's EmbeddedBlue Tranceiver AppMod should take care of the hardware aspect, the user manual for the product gives example code which should get you well on your way to getting your Stamp to talk with a Bluetooth enabled handset.

IR will likely be the most problematic, if your lucky, the handphone will expect the IRDA protocol. This is a fairly well documented protocol so I will leave finding the information on it to you. Parallax's IR buddy pair should take care of the hardware aspect of communicating with your handphone.


08-06-2005, 10:15 PM
Hi Paul

Thanks for the quick reply and the information you have provided. It certainly gave me more food for thoughts now. =)


08-06-2005, 10:21 PM
You would have to use gprs modems (wireless modems) MultiTech is the way to go.

A data sheet from Multitech is attached. The Multitech URL for this modem is

copy and paste this link.
This url is out of data but it will get you to the site anyway
Go to products at catagory pick EXTERNAL DEVICE NETWORKING then

·This is the new URL

Look at drawing this is the only way you can· expence wise do your storage, you cant convert cell phones or tell cell phone companys to make a program for you to fit your needs.

···· I can draw you a cicuit of an dial in auto answer tone decoder if thats is what you need.

·· Short

Post Edited (Short) : 8/7/2005 1:02:29 AM GMT