Cygwin Windows --> Accessing serial port.

Alexander Huemer alexander.huemer at xx.vu
Sun Jun 12 18:20:53 UTC 2011


On Sun, Jun 12, 2011 at 11:11:37PM +0530, R M wrote:
> Why do I need a USB/RS232 cable ?
> 
> If its a laptop, I can understand that they don't come with a serial port so
> you need the converter.
> 
> Many PCs come with a serial port.
> 
> Can I not connect the serial version of the T191 unlock cable to PC serial
> port?
You could, but the RS232 ports that are often present on ATX-style
mainboards provide 12V, which is too much for the phone. 
> 
> As far as I understand, the T191 unlock cable is used to convert RS232
> signal level to 3.3V required by C128.
no. A serial T191 cable does nothing by itself.
> 
> Since I was able to get hold of a serial version of T191 unlock cable as I
> told you in the begining of the mail, I also purchased a USB to Serial
> converter. Its a BAFO BF-810.
> Its based on Prolific chipset.
Unfortunately the prolific chips seem to not work as well for this
purpose as the FTDI chips.
> 
> So I connected first the USB/RS232 converter  ju(BAFO BF-810) and then the
> serial version of the T191 unlock cable.
> 
> Is this the right way ?
>    OR
> Can I just connect the USB/R232 converter (based on Prolific chipset) and
> the use a cable which contains DB9 female on one side and 2.5mm jack on the
> other?
I don't get the difference between those two ways.
> 
> I am asking the second question because you have mentioned in the wiki under
> Hints and Warnings like this:
> 
> If you don't use a 3.3V (low voltage TTL, LVCMOS) serial port you can fry
> your phone! (internally, it connects to the IO-pins of the baseband
> processor which run at 2.8V). *Don't connect directly to your PCs serial
> port (running at +/- 12V!).*
This warning wants to tell you that you should use a USB<-->RS232
converter and not use an onboard port of a PC.

Kind regards
-Alex




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