The BiT Bang Theory

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.

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.

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. 🙂

Later I’ll make a post about the full eLab Hackerspace‘s GSM entry system (now available here) 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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