Hi! Recently I've been developing a GSM access control system for eLab Hackerspace using an old Siemens C55 cell phone and, as such, I needed a data cable to connect it to a PIC microcontroller. I searched on ebay for one but it turned out that they were a little expensive and I began thinking about a way to make myself a data cable.
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Luckily, after searching for a while in my "old power supplies box" (a box where I store all the old phone chargers and power supplies), I found two chargers for old Siemens phones, having the connector that I needed. However, I quickly realized that they only had the VCC and GND pins and I needed a connector with Tx and Rx pins too.
Since I had two chargers I decided to try to modify the connector of one of them to add two more pins and it worked perfectly! :)
The first thing to do was to find out the pinout of the connector to check where I would have to add the pins for Tx and Rx. A quick search on google and I had the pinout (source: pinouts.ru):
1 - Vin - Power charging
2 - Gnd
3 - Tx
4 - Rx
5 - CTS -
6 - RTS
7 - DCD
8 - Audio P
9 - none
10 - Audio N
11 - GND Mic
12 - EPP
So, according to the pinout I had to add pins 3 and 4 to the connector. The first thing to do was to open the case of the connector to access the inside. Then I cut the legs of a resistor and inserted them in the openings for pins 3 and 4. After that I used some pliers to make a small bend on the tip of the pins so that they would make contact when the connector was inserted in the phone, just like the VCC and GND stock pins.
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After putting the pins inside I had to find a cable with four wires to solder them to the four pins. I ended up using a damaged USB cable that I had laying around and removed the USB connector. After soldering the four wires I filled the inside of the connector with hot glue and closed the housing of the connector.
After this small process I finally had a data cable to connect my Siemens C55 to the PIC microcontroller without spending any money at all. :)
Get the flash player here: http://www.adobe.com/flashplayer
Later I'll make a post about the full eLab Hackerspace's GSM entry system so that you can make one for your local hackerspace or just gather some ideas for your next project.
Take care! :)
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