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03-09-2008

Modify T610 USB data cable to use with Microcontroller projects

Bob Carret

About three years ago,I bought a USB data cable to use with T610 mobile phone.I can’t remember what is model just know it is made in China.But now I have a new model mobile phone and my USB data cable not used at all.So I want to modify it to use with my microcontroller projects that use rs232 communication like a USB to RS232 converter.If you have this cable and want to modify this article may help you.

ARK3116 top side PCB
click to enlarge

On the PCB it consist of main IC ARK3116s (I can’t get rich) and PCB PADs for solder like standard RS232 connector pinout show in the figure below.

ark3116s usb to rs232 pinout

These PCB PADs labeld as CTS, DTR, TxD, GND, RTS, RxD, RI, DSR, DCD and 5 V (this pin is not standard RS232 pinout).The most microcontroller projects that use RS232 communication need a null modem without handshaking cable.This means that only the data lines and signal ground are used and cross connected. All other pins have no connection. An example of such a null modem cable without handshaking can be seen in the figure below.

null modem

But a null modem without handshaking cable may not compatible with some software.We can fix this problem by using a null modem with loop back handshaking configuration as show in the figure below.


null modem with loop back handshaking

*DCD some time called CD

When it’s configured as a null modem with loop back handshaking it can be used with the most software that handshaking and no handshaking requires. The photo below is my finished USB to RS232 converter cable that configured as a null modem without handshaking.

usb-to-rs232-converter-box.jpg insert-3mm-led.jpg
solder.jpg finished usb to rs232 converter
Complete with power on LED complete without power on LED
With power status LED Without power status LED

Here is the primary test without connecting to microcontroller(loopback test)

  1. Complete install driver on the included CD-ROM.
  2. Short RxD to TxD pin.
  3. Plug the USB to RS232 converter to computer.You will see new COM PORT in Device Manager window here is COM3(right click My Computer ==> Properties==>in Hardware tab click ==> Device Manager ) like the figure below.

Device manager window

4. Launch HyperTerminal
Start»Programs»Accessories»Communications»HyperTerminal.
and set parameter as show in the figure below.

Hyperterminal

5. Connect to COM3(different for each computer) see in 3.
6. If every thing OK, the text you type will appear in the HyperTerminal window. If you remove the cable and type text, it should not appear in this window.

HyperTerminal

Now the USB data cable ready to use with microcontroller projects as a USB to RS232 converter. More information about null modem configuration check out this website lammertbies. Next time I will use this USB to RS232 converter in my microcontroller projects especially the very popular such Arduino.

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