Hi PICer friends,


referring to my last EMAIL, and appling the previous Jhon Dammeyer and the
Olin Lathrop suggestion, I have cut/past/manipulated this schematics:



PIC out pin ----------|----------------->RX 3.5V device
                      |
                     ___/
                    / Z
                      E
                      N 3.5V
                      E
                      R
                      |
                     GND



PIC RB input <--------------+
with internal               |
pullup acivated             |
                            C
                    BC547    B<---+------TX 3.5V device
                            E     |
                            |     _
                            |     ^
                            |     D1 1n4148
                            |     |
                            +------
                            |
                           GND


but I'm not convinced about the D1 1n4148 because its presence do not permit
at the signal to reach zero level. What happen if I remove it and stay only
with the BC547? (I suppose that the junction BE also do not permit to rech
zero level; it is true?)


To have better wiev, I use the SERIN/SEROUT instruction of PICBASICPRO and
the connection is made a 19200bps, when works ;-)


Regards

Leo


> Rereading our EMAILS, I have understood that the problem that I
> have posted was given in wrong way.
>
> A little history can help.
>
> In normal working condition with PC and the device that I have at
> the begining:
>
> PC COM1: TX----->MAX3232-------->RX 3.5V device
>
> PC COM1: RX<-----MAX3232<--------RX 3.5V device
>
> and works PERFECTLY (obviously because is normal working
> conditions)
>
>
>
>
> Using a PIC powered at 5V instead of a PC:
>
> PIC out pin ----->MAX3232-------->RX 3.5 device
>
>
> PIC in  pin <-----MAX3232<--------TX 3.5 device
>
> and works PERFECTLY!
>
>
>
>
> Trying to remove the MAX3232 (It is not a typing error for MAX232, > but
the version for the 3.5V powered device), maintaining the PIC
> powered at 5V:
>
> PIC out pin -------Diode-Diode--------->RX 3.5 device
>
>
> PIC in  pin <------resistor-------------TX 3.5 device
>
> in this condition I have a working condition, (that means the TX
> and RX levels are near to good) but unreliable.
>
>
> I suppose now you have a better view of my problem.
>
>
> Saluti
>
> Leo
>
> --

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