Cygwin Windows --> Accessing serial port.

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R M rm.engineer84 at gmail.com
Sat Jun 18 13:58:18 UTC 2011


Hi,

If I have a prolific usb to serial converter can I be sure that the
voltage levels that I get is 3.3V and not 5V.

My serial cable seems to be fine. I have done a loopback test and its
echoing whatever I have typed using hyperterminal.

My mobile phone's audio jack is also fine. I am able to use the hands
free feature and listen to the voice.

I hence feel that the 2.5mm male connector of the serial cable is not
properly connecting to the audio jack of the phone though it sits
properly.

Is there a way I can rectify this without buying a new serial cable?

Regards,
RM

On Mon, Jun 13, 2011 at 12:45 AM, Arne <zachso at arcor.de> wrote:
>
> the 3v3 version of max232 is max3232, but this isnt what he needs.
>
> RM, you need a usb->RS232 only if you have no RS232 at one of you
> computers/notebooks available. if you have a normal RS232-port you have
> already everything you need and can use you cable
>
> bye
> arne
>
>
> On Sun, 12 Jun 2011 20:53:49 +0200
> Sébastien Lorquet <squalyl at gmail.com> wrote:
>
> > If you want to use a basic serial port, use a 3.3V version of the
> > good ol' MAX232 (maybe MAX202? can't remember)
> >
> > Sebastien
> >
> > On Sun, Jun 12, 2011 at 8:20 PM, Alexander Huemer
> > <alexander.huemer at xx.vu>wrote:
> >
> > > 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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