Serial Communication With Cell Phones

Hackaday alum [Will O’Brien] has been doing some cellphone integration work. He recently picked up some Motorola c168i cellphones from eBay. It turns out there is a serial port that uses TTL communication with a standard head-phone jack as an interface. [Will] soldered up a connector and used a USB to FTDI cable to interface with the phone. To his surprise he was able to read off the stored text messages even though they were PIN protected in the phone’s operating system. The messages on these units were trivial but this is another example of the importance of clearing your data before discarding your devices.

20 thoughts on “Serial Communication With Cell Phones

  1. This is a perfect platform to connect to a micro and listen to incoming texts. Then based on the incoming texts an action could be performed, starting/unlocking a car. And it could only react to a certain phone number so you dont have to worry about some bozo dialing a wrong number and leaving your car running all day long.

  2. @Addictronics: You mean you’ve had to pause for awhile, right? It seems to me that once you’re addicted to electronics/technology projects, it’s really hard to actually quit, even if funds run short for awhile ;)

    Fun-looking project, btw.

  3. @inventorjack

    Exactly. :) A hiatus more than a true cease in production. Also every time I work on it I find something new that has come out that would work better than what I have. The only think I don’t think that I will ever be replacing is the GPS since it was made before the >60,000 ft ban several years ago, so it will work up to my intended 100,000 ft.

  4. @Robby: No, you see exactly the same pieces of memory as the normal phone interface sees, there’s no hidden log of messages.

    I bought one these as an emergency phone because it was the cheapest option ($20 for the phone, $15 for minutes, $10 mail-in rebate after) and later saw this online:

    After toying with from a terminal and the FTDI USB ttl break-out cable, I found it quite annoying to deal with. The phone’s CPU is rather challenged w/ normal moment-to-moment issues and often misses incoming characters, which means that a microcontroller would have to do a LOT of feed-back checking to ensure it’s commands actually go through. (As I recall, I know you can have it just spit out when a phone call or text arrives, but I don’t think it’ll spit out the body of the text message, only the sender)

    For anyone interested in working with one of these, be sure to read through the AT command list for the G24 which is what you’re really talking to:

  5. I have been doing for almost 4 years.
    I used some old Siemens cellphones like the A56 and my old M55.
    what I did was use a cable RS232 to TTL.
    to normalize the signals I used an HEX inverter between the cable and the phone.
    what I did was a application to execute shell commands sent on SMS.
    To read the SMS from the cellphone I used GAMMU to talk with the phone and my main code was made on TCL and all that under Linux.
    It was a small University project.
    If you find it interesting or need more info please feel free to contact me

  6. siemens M55 (M56 in U?S) was a great phone. my brother and i both had one in high school and i bought a couple more on ebay and kept Franken-phone-ing them together every time one of them broke ( we were really rough on them) i lost one for a few months and when i found it in the ground, with mud all over its chips..
    it didnt work. so i had to franken-phone it together to recover my data.
    i use to text all day long, never having to look at what i was typing. i wish someone would make a phone that cool with modern-technology (although COLOR LCD was top-of the line back then)
    i didn have any trouble getting it to run all kinds of java programs. nowadays you have to use the master key and operator code. but the lights, they were fun to bust out at a club, or a concert, or when you’re in the dark and someone is rollin’

Leave a Reply

Please be kind and respectful to help make the comments section excellent. (Comment Policy)

This site uses Akismet to reduce spam. Learn how your comment data is processed.