Re: TTL serial cable: are they useless?
Rufus Kohn <[email protected]>
| Newsgroups | gmane.comp.systems.newton.newtontalk |
|---|---|
| Message-ID | <[email protected]> |
Thank you Bernie for taking the time to clarify the difference. You made it very clear. Rufus Kohn . > Op 12 mei 2019 om 03:34 heeft [email protected] het volgende geschreven: > > 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 >> > > ---------------------------------------------------------------------- > > http://newtontalk.net/ > http://twitter.com/newtontalk ---------------------------------------------------------------------- http://newtontalk.net/ http://twitter.com/newtontalk