Hi,

if I have correctly understand the TX section should be:

                                R1
 PIC out pin TX >-------------/\/\/\----------> RX 3.5V device
  19200 bps                     1K                (no RS232)


without the 3.5 zener. Is for the R1 the 1K the best value?






The revised receiving section should be:

                          +5V
                          ---
                           \
                           /
                        R2 \ 10K
                           /
                           \
                           |
 PIC RB RX <---------------+
 no UART                   |
 (bit banging)             |
                           C            R3
                   BC547    B<---+----/\/\/\----< TX 3.5V device
                           E     |      1K         19200 bps
                           |     |                 (no RS232)
                           |     |
                           |    ___
                           |     ^    D1 1n4148
                           |     |
                           |     |
                           +------
                           |
                          GND


For R3, is 1K the best value?


Regards

Leo

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