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TUCoPS :: Hardware Hacks :: hp48sxir.htm

Instructions for the HP48SX IR Decoder



INSTRUCTONS FOR THE HP48SX IR DECODER

-\/\/--    resistor

!
\
/
\    resistor
/
!

  !!
--!!-- capacitor
  !!

   !--!
  +!  !+
 -!!  !!-   Quartz Crystal
  +!  !+
   !--!


!/
!     NPN transistor
!\!
 -

\\
>>
! /
!/
!\    IR phototransistor
! \!
 -

 ! >>
 V//
---  IR LED
 !

 !\
-! >o-   NOT gate
 !/

-!\
 ! )-   AND gate
-!/

-)
 )
-)--\
 )   >o-- NOR gate
-)--/
 )
-)

Good Luck!
I am on ARD@UK.AC.BRIS.SIVA (JANET) = internet ARD@siva.bris.ac.uk

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!\  P/transistor                             !  !  ---------       !
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                2.45MHz                       !----!   !----!  !   !
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    !   !/   ! +!  !+  !   !/       !  !/     !R  D!-+ !R  D!  !   !
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                ! !                                            !   !
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  ----     !!        !! 4*22u                                  !   !
   !     +-!!-+    +-!!-+                                      !   !
   !     ! !! !    ! !! !                                      !   !
   !     !    !    !    !                                      !   !
   !    -------------------                                    !   !
   !    !  C1       C2    !  +---------------------------------)---+
   +----!Vcc              !  !                                 !
  ---   !                 !  !                                 !  +5
  ---+  !                 !  !                                 ! ----
   +----!+10v             !  !                                 !  !  >>
        !                 !  !   +-----------------------------+  V //
 PC     !                 !  !   !    '393                       ---
RS232   !                 !  !   !   !----!                       ! IR
  >-----!TxO1         TxI1!--+   !   !   A!              +-/\/\---+ LED
 Tx     !                 !      !   !   B!       2N3904 ! 56R
        !TxO2         TxI2!      +---!>  C!            !/
        !                 !  +-------!R  D!----/\/\----!
  >-----!RxI1         RxO1!--+       !----!    1k2     !\!
 Rx     !                 !                            - !
        !RxI2         RxO2!                              !
        !                 !                             ---
  >--+  !  -10V     Gnd   !                             ///
 Sg  !  -------------------
     !       !  !!  !
     !       +--!!--+
     !          !!  !
    ---          +  !
    ///             !
                   ---
                   ///


HP IR FORMAT BELOW

Taken from ioguide.doc, ftp from ftp hpcvbbs.cv.hp.com, dir pub

The IR port allows half-duplex communication between systems at 2400 baud using pulses of infrared light instead of wires. Full-duplex is not used due to the need to suppress reflections. The format for IR transmission is similar to serial transmission except that a pulse of infrared light of 52 Ns duration (nominal) is used to transmit a zero-bit. The absence of a pulse indicates a one-bit or idle condition. Note that if the pulses are stretched out to fill a bit time this becomes very similar to the serial signal.



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