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Re: Can I connect TTL devices together.

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  • Silas
    ... If you look at the stowaway hardware reference manual [http://www.splorp.com/pdf/ stowawayhwref.pdf] it stats that the Handspring edition of the keyboard
    Message 1 of 3 , Jul 6, 2007
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      --- In zipitwireless@yahoogroups.com, "Barbudor" <barbudor@...> wrote:
      >
      > Silas,
      >
      > What make you think the Stowaway is TTL ?

      If you look at the stowaway hardware reference manual [http://www.splorp.com/pdf/
      stowawayhwref.pdf] it stats that the Handspring edition of the keyboard is TTL look at
      page 14.


      > It connects to a PALM and on my PALM IIIx
      > the serial connection is direct to PC RS232, without any
      > adapter.
      >
      > Did you just measured signals ? Don't conclude that it is TTL
      > just becuase the signal range is 0..5V. It may just be because
      > it use a tolrance of the PALM input.
      > TTL serial use a positive logic while RS232 use negative logic:
      > - for a 0 bit, TTL is at 0V and RS232 is at +3..12V
      > - for a 1 bit, TTL is at 5V and RS232 is at -3..12V
      > A TTL/RS232 converter is basicaly a inverter + voltage shifter.
      > Note that default state and stop bit is 1, start bit is 0.
      >
      > By the Way the ZipIt is not TTL but LVTTL at 3.3V

      Good because VCC of the Stowaway can be 3.0V DC to 5.5V DC.

      >
      > So I feel that you will need an simple inverter such as a 74LV07
      > so they talk the same logic.

      I will look into that.

      >
      > Note that this is very quick thoughts. Did not even looked back
      > at the PALM schematics.

      Thank. It got my brain going again. I almost still think that I should convert both to serial,
      just so I have have the serial port.


      >
      > Regards,
      >
      > ~barbudor~
      >
      > ----- Original Message -----
      > From: "Silas" <silas.baronda@...>
      > To: <zipitwireless@yahoogroups.com>
      > Sent: Thursday, July 05, 2007 4:53 PM
      > Subject: [zipitwireless] Can I connect TTL devices together.
      >
      >
      > I have a TTL keyboard that I want to adapt to the zipit. If the zipit
      > is already TTL can I just connect the keyboard directly to the zipit
      > because it is TTL?
      >
      > If not, would I have to convert each device to rs-232 and then connect
      > the serial port together?
      >
      > P.S. I'm trying to connect a Visor Storaway keyboard to my zipit.
      >
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