Re: TTL serial cable: are they useless?

Is thuis a werking cable?

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Op zo 12 mei 2019 03:36 schreef <[email protected]>:

> Hi Rufus,
>
> The simple answer is the TTL cable is no good..
>
> BUT the long answer is
>
> The difference between the TTL cable and the RS232 cable is the voltage
> levels used.
>
> TTL uses TTL voltage levels of 0V for 0 and 5V for 1
> RS232 uses between +3 and+12V for 0 and -3 and -12V for 1
>
> TTL cables are intended for direct connection to say a microcontroler but
> RS232 is intended for long distance communications.
>
> To add to the confusion the Newton actual uses RS422 for the data comms
> which is a differential singling system which is basically double RS232 it
> has 2 transmit lines and 2 rx lines (one is the inverse of the other) to
> use rs232 you tie one to ground and use the other (to maintain the correct
> voltage polarity for the signal)
> As you might have noticed RS232 (and422) have a wide valid voltage range 3
> to 12V so it is possible to invert the TTL signal with a CMOS inverter and
> it usually works. The CMOS inverter is required because it can accept a
> possible 12V into it.
>
> Sorry the more I type the more involved this is becoming :-)
>
> Now depending on the ACTUAL voltage output by the Newton - it could be
> anywhere from 3 - 12V Ive never measured it but if it is no more than 5V it
> could be possible to use the +Ve data pins (6 and 7) and tie the -Ve data
> pins 3 and 5 to gnd (this is the opposite to what is required for RS232 )
> and use the TTL cable. NOTE I have not tried this or made the appropriate
> measurements it is just theoretically possible. I would not just TRY it
> with out making measurements first or damage may result.
>
> Regards
>
> Bernie
>
>
> > On 12 May 2019, at 06:19, Rufus Kohn <[email protected]> wrote:
> >
> > Hi
> > I bought a TTL serial to usb cable and found out it wont work with the
> > Newton. The mac recognizes the FDTI chipset but it is not possible to
> > connect via NCX. So i bought the correct cable but it left me wondering
> > exactly whet the difference is between the two.
> > They look identical.
> > Is the difference hardware? Like are the wires hooked up in a different
> > way? Could I switch them around to make it work?
> >
> > Or is it a software difference and it will never work on a newton?
> > Who can enlighten me?
> > --
> > Met hartelijke groet,
> >
> > Rufus Kohn
> > 0613159031
> > ----------------------------------------------------------------------
> >
> > http://newtontalk.net/
> > http://twitter.com/newtontalk
> >
>
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